[Code of Federal Regulations]
[Title 40, Volume 2]
[Revised as of July 1, 2002]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR50]

[Page 5-128]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
               CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY
 
PART 50--NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY STANDARDS--Table of Contents

Sec.
50.1  Definitions.
50.2  Scope.
50.3  Reference conditions.
50.4  National primary ambient air quality standards for sulfur oxides 
          (sulfur dioxide).
50.5  National secondary ambient air quality standard for sulfur oxides 
          (sulfur dioxide).
50.6  National primary and secondary ambient air quality standards for 
          PM<INF>10</INF>.
50.7  National primary and secondary ambient air quality standards for 
          particulate matter.
50.8  National primary ambient air quality standards for carbon 
          monoxide.
50.9  National 1-hour primary and secondary ambient air quality 
          standards for ozone.
50.10  National 8-hour primary and secondary ambient air quality 
          standards for ozone.
50.11  National primary and secondary ambient air quality standards for 
          nitrogen dioxide.
50.12  National primary and secondary ambient air quality standards for 
          lead.

Appendix A to Part 50--Reference Method for the Determination of Sulfur 
          Dioxide in the Atmosphere (Pararosaniline Method)
Appendix B to Part 50--Reference Method for the Determination of 
          Suspended Particulate Matter in the Atmosphere (High-Volume 
          Method)
Appendix C to Part 50--Measurement Principle and Calibration Procedure 
          for the Measurement of Carbon Monoxide in the Atmosphere (Non-
          Dispersive Infrared Photometry)
Appendix D to Part 50--Measurement Principle and Calibration Procedure 
          for the Measurement of Ozone in the Atmosphere
Appendix E to Part 50 [Reserved]
Appendix F to Part 50--Measurement Principle and Calibration Procedure 
          for the Measurement of Nitrogen Dioxide in the Atmosphere (Gas 
          Phase Chemiluminescence)
Appendix G to Part 50--Reference Method for the Determination of Lead in 
          Suspended Particulate Matter Collected From Ambient Air
Appendix H to Part 50--Interpretation of the 1-Hour Primary and 
          Secondary National Ambient Air Quality Standards for Ozone
Appendix I to Part 50--Interpretation of the 8-Hour Primary and 
          Secondary National Ambient Air Quality Standards for Ozone
Appendix J to Part 50--Reference Method for the Determination of 
          Particulate Matter as PM<INF>10</INF> in the Atmosphere
Appendix K to Part 50--Interpretation of the National Ambient Air 
          Quality Standards for Particulate Matter
Appendix L to Part 50--Reference Method for the Determination of Fine 
          Particulate Matter as PM<INF>2.5</INF> in the Atmosphere
Appendix M to Part 50--Reference Method for the Determination of 
          Particulate Matter as PM<INF>10</INF> in the Atmosphere
Appendix N to Part 50--Interpretation of the National Ambient Air 
          Quality Standards for Particulate Matter

    Authority: 42 U.S.C. 7401, et seq.

    Source: 36 FR 22384, Nov. 25, 1971, unless otherwise noted.

Sec. 50.1  Definitions.

    (a) As used in this part, all terms not defined herein shall have 
the meaning given them by the Act.
    (b) Act means the Clean Air Act, as amended (42 U.S.C. 1857-18571, 
as amended by Pub. L. 91-604).
    (c) Agency means the Environmental Protection Agency.
    (d) Administrator means the Administrator of the Environmental 
Protection Agency.
    (e) Ambient air means that portion of the atmosphere, external to 
buildings, to which the general public has access.
    (f) Reference method means a method of sampling and analyzing the 
ambient air for an air pollutant that is specified as a reference method 
in an appendix to this part, or a method that has been designated as a 
reference method in accordance with part 53 of this chapter; it does not 
include a method for which a reference method designation has been 
cancelled in accordance with Sec. 53.11 or Sec. 53.16 of this chapter.
    (g) Equivalent method means a method of sampling and analyzing the 
ambient air for an air pollutant that has been designated as an 
equivalent method in accordance with part 53 of this chapter; it does 
not include a method for which an equivalent method designation has

[[Page 6]]

been cancelled in accordance with Sec. 53.11 or Sec. 53.16 of this 
chapter.
    (h) Traceable means that a local standard has been compared and 
certified either directly or via not more than one intermediate 
standard, to a primary standard such as a National Bureau of Standards 
Standard Reference Material (NBS SRM), or a USEPA/NBS-approved Certified 
Reference Material (CRM).
    (i) Indian country is as defined in 18 U.S.C. 1151.

[36 FR 22384, Nov. 25, 1971, as amended at 41 FR 11253, Mar. 17, 1976; 
48 FR 2529, Jan. 20, 1983; 63 FR 7274, Feb. 12, 1998]

Sec. 50.2  Scope.

    (a) National primary and secondary ambient air quality standards 
under section 109 of the Act are set forth in this part.
    (b) National primary ambient air quality standards define levels of 
air quality which the Administrator judges are necessary, with an 
adequate margin of safety, to protect the public health. National 
secondary ambient air quality standards define levels of air quality 
which the Administrator judges necessary to protect the public welfare 
from any known or anticipated adverse effects of a pollutant. Such 
standards are subject to revision, and additional primary and secondary 
standards may be promulgated as the Administrator deems necessary to 
protect the public health and welfare.
    (c) The promulgation of national primary and secondary ambient air 
quality standards shall not be considered in any manner to allow 
significant deterioration of existing air quality in any portion of any 
State or Indian country.
    (d) The proposal, promulgation, or revision of national primary and 
secondary ambient air quality standards shall not prohibit any State or 
Indian country from establishing ambient air quality standards for that 
State or area under a tribal CAA program or any portion thereof which 
are more stringent than the national standards.

[36 FR 22384, Nov. 25, 1971, as amended at 63 FR 7274, Feb. 12, 1998]

Sec. 50.3   Reference conditions.

    All measurements of air quality that are expressed as mass per unit 
volume (e.g., micrograms per cubic meter) other than for the particulate 
matter (PM<INF>10</INF> and PM<INF>2.5</INF>) standards contained in 
Sec. 50.7 shall be corrected to a reference temperature of 25 
<degree<ls-thn-eq>C and a reference pressure of 760 millimeters of 
mercury (1,013.2 millibars). Measurements of PM<INF>10</INF> and 
PM<INF>2.5</INF> for purposes of comparison to the standards contained 
in Sec. 50.7 shall be reported based on actual ambient air volume 
measured at the actual ambient temperature and pressure at the 
monitoring site during the measurement period.

[62 FR 38711, July 18, 1997]

Sec. 50.4  National primary ambient air quality standards for sulfur 
          oxides (sulfur dioxide).

    (a) The level of the annual standard is 0.030 parts per million 
(ppm), not to be exceeded in a calendar year. The annual arithmetic mean 
shall be rounded to three decimal places (fractional parts equal to or 
greater than 0.0005 ppm shall be rounded up).
    (b) The level of the 24-hour standard is 0.14 parts per million 
(ppm), not to be exceeded more than once per calendar year. The 24-hour 
averages shall be determined from successive nonoverlapping 24-hour 
blocks starting at midnight each calendar day and shall be rounded to 
two decimal places (fractional parts equal to or greater than 0.005 ppm 
shall be rounded up).
    (c) Sulfur oxides shall be measured in the ambient air as sulfur 
dioxide by the reference method described in appendix A to this part or 
by an equivalent method designated in accordance with part 53 of this 
chapter.
    (d) To demonstrate attainment, the annual arithmetic mean and the 
second-highest 24-hour averages must be based upon hourly data that are 
at least 75 percent complete in each calendar quarter. A 24-hour block 
average shall be considered valid if at least 75 percent of the hourly 
averages for the 24-hour period are available. In the event that only 
18, 19, 20, 21, 22, or 23 hourly averages are available, the 24-hour 
block average shall be computed as the sum of the available hourly

[[Page 7]]

averages using 18, 19, etc. as the divisor. If fewer than 18 hourly 
averages are available, but the 24-hour average would exceed the level 
of the standard when zeros are substituted for the missing values, 
subject to the rounding rule of paragraph (b) of this section, then this 
shall be considered a valid 24-hour average. In this case, the 24-hour 
block average shall be computed as the sum of the available hourly 
averages divided by 24.

[61 FR 25579, May 22, 1996]

Sec. 50.5  National secondary ambient air quality standard for sulfur 
          oxides (sulfur dioxide).

    (a) The level of the 3-hour standard is 0.5 parts per million (ppm), 
not to be exceeded more than once per calendar year. The 3-hour averages 
shall be determined from successive nonoverlapping 3-hour blocks 
starting at midnight each calendar day and shall be rounded to 1 decimal 
place (fractional parts equal to or greater than 0.05 ppm shall be 
rounded up).
    (b) Sulfur oxides shall be measured in the ambient air as sulfur 
dioxide by the reference method described in appendix A of this part or 
by an equivalent method designated in accordance with part 53 of this 
chapter.
    (c) To demonstrate attainment, the second-highest 3-hour average 
must be based upon hourly data that are at least 75 percent complete in 
each calendar quarter. A 3-hour block average shall be considered valid 
only if all three hourly averages for the 3-hour period are available. 
If only one or two hourly averages are available, but the 3-hour average 
would exceed the level of the standard when zeros are substituted for 
the missing values, subject to the rounding rule of paragraph (a) of 
this section, then this shall be considered a valid 3-hour average. In 
all cases, the 3-hour block average shall be computed as the sum of the 
hourly averages divided by 3.

[61 FR 25580, May 22, 1996]

Sec. 50.6   National primary and secondary ambient air quality standards 
          for PM<INF>10</INF>.

    (a) The level of the national primary and secondary 24-hour ambient 
air quality standards for particulate matter is 150 micrograms per cubic 
meter (<greek mu<ls-thn-eq>g/m\3\), 24-hour average concentration. The 
standards are attained when the expected number of days per calendar 
year with a 24-hour average concentration above 150 <greek 
mu<ls-thn-eq>g/m\3\, as determined in accordance with appendix K to this 
part, is equal to or less than one.
    (b) The level of the national primary and secondary annual standards 
for particulate matter is 50 micrograms per cubic meter (<greek 
mu<ls-thn-eq>g/m\3\), annual arithmetic mean. The standards are attained 
when the expected annual arithmetic mean concentration, as determined in 
accordance with appendix K to this part, is less than or equal to 50 
<greek mu<ls-thn-eq>g/m\3\.
    (c) For the purpose of determining attainment of the primary and 
secondary standards, particulate matter shall be measured in the ambient 
air as PM<INF>10</INF> (particles with an aerodynamic diameter less than 
or equal to a nominal 10 micrometers) by:
    (1) A reference method based on appendix J and designated in 
accordance with part 53 of this chapter, or
    (2) An equivalent method designated in accordance with part 53 of 
this chapter.

[52 FR 24663, July 1, 1987, as amended at 62 FR 38711, July 18, 1997; 65 
FR 80779, Dec. 22, 2000]

Sec. 50.7   National primary and secondary ambient air quality standards 
          for particulate matter.

    (a) The national primary and secondary ambient air quality standards 
for particulate matter are:
    (1) 15.0 micrograms per cubic meter (<greek mu<ls-thn-eq>g/m\3\) 
annual arithmetic mean concentration, and 65 <greek mu<ls-thn-eq>g/m\3\ 
24-hour average concentration measured in the ambient air as 
PM<INF>2.5</INF> (particles with an aerodynamic diameter less than or 
equal to a nominal 2.5 micrometers) by either:
    (i) A reference method based on appendix L of this part and 
designated in accordance with part 53 of this chapter; or
    (ii) An equivalent method designated in accordance with part 53 of 
this chapter.

[[Page 8]]

    (2) 50 micrograms per cubic meter (<greek mu<ls-thn-eq>g/m\3\) 
annual arithmetic mean concentration, and 150 <greek mu<ls-thn-eq>g/m\3\ 
24-hour average concentration measured in the ambient air as 
PM<INF>10</INF> (particles with an aerodynamic diameter less than or 
equal to a nominal 10 micrometers) by either:
    (i) A reference method based on appendix M of this part and 
designated in accordance with part 53 of this chapter; or
    (ii) An equivalent method designated in accordance with part 53 of 
this chapter.
    (b) The annual primary and secondary PM<INF>2.5</INF> standards are 
met when the annual arithmetic mean concentration, as determined in 
accordance with appendix N of this part, is less than or equal to 15.0 
micrograms per cubic meter.
    (c) The 24-hour primary and secondary PM<INF>2.5</INF> standards are 
met when the 98<SUP>th</SUP> percentile 24-hour concentration, as 
determined in accordance with appendix N of this part, is less than or 
equal to 65 micrograms per cubic meter.
    (d) The annual primary and secondary PM<INF>10</INF> standards are 
met when the annual arithmetic mean concentration, as determined in 
accordance with appendix N of this part, is less than or equal to 50 
micrograms per cubic meter.
    (e) The 24-hour primary and secondary PM<INF>10</INF> standards are 
met when the 99<SUP>th</SUP> percentile 24-hour concentration, as 
determined in accordance with appendix N of this part, is less than or 
equal to 150 micrograms per cubic meter.

[62 FR 38711, July 18, 1997]

Sec. 50.8  National primary ambient air quality standards for carbon 
          monoxide.

    (a) The national primary ambient air quality standards for carbon 
monoxide are:
    (1) 9 parts per million (10 milligrams per cubic meter) for an 8-
hour average concentration not to be exceeded more than once per year 
and
    (2) 35 parts per million (40 milligrams per cubic meter) for a 1-
hour average concentration not to be exceeded more than once per year.
    (b) The levels of carbon monoxide in the ambient air shall be 
measured by:
    (1) A reference method based on appendix C and designated in 
accordance with part 53 of this chapter, or
    (2) An equivalent method designated in accordance with part 53 of 
this chapter.
    (c) An 8-hour average shall be considered valid if at least 75 
percent of the hourly average for the 8-hour period are available. In 
the event that only six (or seven) hourly averages are available, the 8-
hour average shall be computed on the basis of the hours available using 
six (or seven) as the divisor.
    (d) When summarizing data for comparision with the standards, 
averages shall be stated to one decimal place. Comparison of the data 
with the levels of the standards in parts per million shall be made in 
terms of integers with fractional parts of 0.5 or greater rounding up.

[50 FR 37501, Sept. 13, 1985]

Sec. 50.9   National 1-hour primary and secondary ambient air quality 
          standards for ozone.

    (a) The level of the national 1-hour primary and secondary ambient 
air quality standards for ozone measured by a reference method based on 
appendix D to this part and designated in accordance with part 53 of 
this chapter, is 0.12 parts per million (235 <greek mu<ls-thn-eq>g/
m\3\). The standard is attained when the expected number of days per 
calendar year with maximum hourly average concentrations above 0.12 
parts per million (235 <greek mu<ls-thn-eq>g/m\3\) is equal to or less 
than 1, as determined by appendix H to this part.
    (b) The 1-hour standards set forth in this section will remain 
applicable to all areas notwithstanding the promulgation of 8-hour ozone 
standards under Sec. 50.10. In addition, after the 8-hour standard has 
become fully enforceable under part D of title I of the CAA and subject 
to no further legal challenge, the 1-hour standards set forth in this 
section will no longer apply to an area once EPA determines that the 
area has

[[Page 9]]

air quality meeting the 1-hour standard. Area designations and 
classifications with respect to the 1-hour standards are codified in 40 
CFR part 81.

[62 FR 38894, July 18, 1997, as amended at 65 FR 45200, July 20, 2000]

Sec. 50.10   National 8-hour primary and secondary ambient air quality 
          standards for ozone.

    (a) The level of the national 8-hour primary and secondary ambient 
air quality standards for ozone, measured by a reference method based on 
appendix D to this part and designated in accordance with part 53 of 
this chapter, is 0.08 parts per million (ppm), daily maximum 8-hour 
average.
    (b) The 8-hour primary and secondary ozone ambient air quality 
standards are met at an ambient air quality monitoring site when the 
average of the annual fourth-highest daily maximum 8-hour average ozone 
concentration is less than or equal to 0.08 ppm, as determined in 
accordance with appendix I to this part.

[62 FR 38894, July 18, 1997]

Sec. 50.11  National primary and secondary ambient air quality standards 
          for nitrogen dioxide.

    (a) The level of the national primary ambient air quality standard 
for nitrogen dioxide is 0.053 parts per million (100 micrograms per 
cubic meter), annual arithmetic mean concentration.
    (b) The level of national secondary ambient air quality standard for 
nitrogen dioxide is 0.053 parts per million (100 micrograms per cubic 
meter), annual arithmetic mean concentration.
    (c) The levels of the standards shall be measured by:
    (1) A reference method based on appendix F and designated in 
accordance with part 53 of this chapter, or
    (2) An equivalent method designated in accordance with part 53 of 
this chapter.
    (d) The standards are attained when the annual arithmetic mean 
concentration in a calendar year is less than or equal to 0.053 ppm, 
rounded to three decimal places (fractional parts equal to or greater 
than 0.0005 ppm must be rounded up). To demonstrate attainment, an 
annual mean must be based upon hourly data that are at least 75 percent 
complete or upon data derived from manual methods that are at least 75 
percent complete for the scheduled sampling days in each calendar 
quarter.

[50 FR 25544, June 19, 1985]

Sec. 50.12  National primary and secondary ambient air quality standards 
          for lead.

    National primary and secondary ambient air quality standards for 
lead and its compounds, measured as elemental lead by a reference method 
based on appendix G to this part, or by an equivalent method, are: 1.5 
micrograms per cubic meter, maximum arithmetic mean averaged over a 
calendar quarter.

(Secs. 109, 301(a) Clean Air Act as amended (42 U.S.C. 7409, 7601(a)))

[43 FR 46258, Oct. 5, 1978]

Appendix A to Part 50--Reference Method for the Determination of Sulfur 
            Dioxide in the Atmosphere (Pararosaniline Method)

    1.0 Applicability.
    1.1 This method provides a measurement of the concentration of 
sulfur dioxide (SO<INF>2</INF>) in ambient air for determining 
compliance with the primary and secondary national ambient air quality 
standards for sulfur oxides (sulfur dioxide) as specified in Sec. 50.4 
and Sec. 50.5 of this chapter. The method is applicable to the 
measurement of ambient SO<INF>2</INF> concentrations using sampling 
periods ranging from 30 minutes to 24 hours. Additional quality 
assurance procedures and guidance are provided in part 58, appendixes A 
and B, of this chapter and in references 1 and 2.
    2.0 Principle.
    2.1 A measured volume of air is bubbled through a solution of 0.04 M 
potassium tetrachloromercurate (TCM). The SO<INF>2</INF> present in the 
air stream reacts with the TCM solution to form a stable 
monochlorosulfonatomercurate(3) complex. Once formed, this complex 
resists air oxidation(4, 5) and is stable in the presence of strong 
oxidants such as ozone and oxides of nitrogen. During subsequent 
analysis, the complex is reacted with acid-bleached pararosaniline dye 
and formaldehyde to form an intensely colored pararosaniline methyl 
sulfonic acid.(6) The optical density of this species is determined 
spectrophotometrically at 548 nm and is directly related to the amount 
of SO<INF>2</INF> collected. The total volume of air sampled, corrected 
to EPA reference conditions (25  deg.C, 760 mm Hg [101 kPa]), is 
determined from the measured flow rate and the sampling time. The 
concentration of SO<INF>2</INF> in

[[Page 10]]

the ambient air is computed and expressed in micrograms per standard 
cubic meter (<greek mu<ls-thn-eq>g/std m\3\).
    3.0 Range.
    3.1 The lower limit of detection of SO<INF>2</INF> in 10 mL of TCM 
is 0.75 <greek mu<ls-thn-eq>g (based on collaborative test results).(7) 
This represents a concentration of 25 <greek mu<ls-thn-eq>g 
SO<INF>2</INF>/m\3\ (0.01 ppm) in an air sample of 30 standard liters 
(short-term sampling) and a concentration of 13 <greek mu<ls-thn-eq>g 
SO<INF>2</INF>/m\3\ (0.005 ppm) in an air sample of 288 standard liters 
(long-term sampling). Concentrations less than 25 <greek mu<ls-thn-eq>g 
SO<INF>2</INF>/m\3\ can be measured by sampling larger volumes of 
ambient air; however, the collection efficiency falls off rapidly at low 
concentrations.(8, 9) Beer's law is adhered to up to 34 <greek 
mu<ls-thn-eq>g of SO<INF>2</INF> in 25 mL of final solution. This upper 
limit of the analysis range represents a concentration of 1,130 <greek 
mu<ls-thn-eq>g SO<INF>2</INF>/m\3\ (0.43 ppm) in an air sample of 30 
standard liters and a concentration of 590 <greek mu<ls-thn-eq>g 
SO<INF>2</INF>/m\3\ (0.23 ppm) in an air sample of 288 standard liters. 
Higher concentrations can be measured by collecting a smaller volume of 
air, by increasing the volume of absorbing solution, or by diluting a 
suitable portion of the collected sample with absorbing solution prior 
to analysis.
    4.0 Interferences.
    4.1 The effects of the principal potential interferences have been 
minimized or eliminated in the following manner: Nitrogen oxides by the 
addition of sulfamic acid,(10, 11) heavy metals by the addition of 
ethylenediamine tetracetic acid disodium salt (EDTA) and phosphoric 
acid,(10, 12) and ozone by time delay.(10) Up to 60 <greek 
mu<ls-thn-eq>g Fe (III), 22 <greek mu<ls-thn-eq>g V (V), 10 <greek 
mu<ls-thn-eq>g Cu (II), 10 <greek mu<ls-thn-eq>g Mn (II), and 10 <greek 
mu<ls-thn-eq>g Cr (III) in 10 mL absorbing reagent can be tolerated in 
the procedure.(10) No significant interference has been encountered with 
2.3 <greek mu<ls-thn-eq>g NH<INF>3</INF>.(13)
    5.0 Precision and Accuracy.
    5.1 The precision of the analysis is 4.6 percent (at the 95 percent 
confidence level) based on the analysis of standard sulfite samples.(10)
    5.2 Collaborative test results (14) based on the analysis of 
synthetic test atmospheres (SO<INF>2</INF> in scrubbed air) using the 
24-hour sampling procedure and the sulfite-TCM calibration procedure 
show that:

<bullet<ls-thn-eq> The replication error varies linearly with 
concentration from +/-2.5 <greek mu<ls-thn-eq>g/m\3\ at concentrations 
of 100 <greek mu<ls-thn-eq>g/m\3\ to +/-7 <greek mu<ls-thn-eq>g/m\3\ at 
concentrations of 400 <greek mu<ls-thn-eq>g/m\3\.
<bullet<ls-thn-eq> The day-to-day variability within an individual 
laboratory (repeatability) varies linearly with concentration from +/-
18.1 <greek mu<ls-thn-eq>g/m\3\ at levels of 100 <greek mu<ls-thn-eq>g/
m\3\ to +/-50.9 <greek mu<ls-thn-eq>g/m\3\ at levels of 400 <greek 
mu<ls-thn-eq>g/m\3\.
<bullet<ls-thn-eq> The day-to-day variability between two or more 
laboratories (reproducibility) varies linearly with concentration from 
+/-36.9 <greek mu<ls-thn-eq>g/m\3\ at levels of 100 <greek 
mu<ls-thn-eq>g/m\3\ to +/-103.5 <greek mu<ls-thn-eq> g/m\3\ at levels of 
400 <greek mu<ls-thn-eq>g/m\3\.
<bullet<ls-thn-eq> The method has a concentration-dependent bias, which 
becomes significant at the 95 percent confidence level at the high 
concentration level. Observed values tend to be lower than the expected 
SO<INF>2</INF> concentration level.

    6.0 Stability.
    6.1 By sampling in a controlled temperature environment of 
15 deg.+\10  deg.C, greater than 98.9 percent of the SO<INF>2</INF>-TCM 
complex is retained at the completion of sampling. (15) If kept at 5 
deg.C following the completion of sampling, the collected sample has 
been found to be stable for up to 30 days.(10) The presence of EDTA 
enhances the stability of SO<INF>2</INF> in the TCM solution and the 
rate of decay is independent of the concentration of SO<INF>2</INF>.(16)
    7.0 Apparatus.
    7.1 Sampling.
    7.1.1 Sample probe: A sample probe meeting the requirements of 
section 7 of 40 CFR part 58, appendix E (Teflon<register 
mark<ls-thn-eq>; or glass with residence time less than 20 sec.) is used 
to transport ambient air to the sampling train location. The end of the 
probe should be designed or oriented to preclude the sampling of 
precipitation, large particles, etc. A suitable probe can be constructed 
from Teflon&reg; tubing connected to an inverted funnel.
    7.1.2 Absorber--short-term sampling: An all glass midget impinger 
having a solution capacity of 30 mL and a stem clearance of 4+/-1 mm 
from the bottom of the vessel is used for sampling periods of 30 minutes 
and 1 hour (or any period considerably less than 24 hours). Such an 
impinger is shown in Figure 1. These impingers are commercially 
available from distributors such as Ace Glass, Incorporated.
    7.1.3 Absorber--24-hour sampling: A polypropylene tube 32 mm in 
diameter and 164 mm long (available from Bel Art Products, Pequammock, 
NJ) is used as the absorber. The cap of the absorber must be a 
polypropylene cap with two ports (rubber stoppers are unacceptable 
because the absorbing reagent can react with the stopper to yield 
erroneously high SO<INF>2</INF> concentrations). A glass impinger stem, 
6 mm in diameter and 158 mm long, is inserted into one port of the 
absorber cap. The tip of the stem is tapered to a small diameter orifice 
(0.4+\0.1 mm) such that a No. 79 jeweler's drill bit will pass through 
the opening but a No. 78 drill bit will not. Clearance from the bottom 
of the absorber to the tip of the stem must be 6+\2 mm. Glass stems can 
be fabricated by any reputable glass blower or can be obtained from a 
scientific supply firm. Upon receipt, the orifice test should be 
performed to verify the orifice size. The 50 mL volume level should be 
permanently marked on the absorber. The assembled absorber is shown in 
Figure 2.
    7.1.4 Moisture trap: A moisture trap constructed of a glass trap as 
shown in Figure 1 or a polypropylene tube as shown in Figure 2 is placed 
between the absorber tube and

[[Page 11]]

flow control device to prevent entrained liquid from reaching the flow 
control device. The tube is packed with indicating silica gel as shown 
in Figure 2. Glass wool may be substituted for silica gel when 
collecting short-term samples (1 hour or less) as shown in Figure 1, or 
for long term (24 hour) samples if flow changes are not routinely 
encountered.
    7.1.5 Cap seals: The absorber and moisture trap caps must seal 
securely to prevent leaks during use. Heat-shrink material as shown in 
Figure 2 can be used to retain the cap seals if there is any chance of 
the caps coming loose during sampling, shipment, or storage.
<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

[[Page 12]]

<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

[[Page 13]]

    7.1.6 Flow control device: A calibrated rotameter and needle valve 
combination capable of maintaining and measuring air flow to within +\2 
percent is suitable for short-term sampling but may not be used for 
long-term sampling. A critical orifice can be used for regulating flow 
rate for both long-term and short-term sampling. A 22-gauge hypodermic 
needle 25 mm long may be used as a critical orifice to yield a flow rate 
of approximately 1 L/min for a 30-minute sampling period. When sampling 
for 1 hour, a 23-gauge hypodermic needle 16 mm in length will provide a 
flow rate of approximately 0.5 L/min. Flow control for a 24-hour sample 
may be provided by a 27-gauge hypodermic needle critical orifice that is 
9.5 mm in length. The flow rate should be in the range of 0.18 to 0.22 
L/min.
    7.1.7 Flow measurement device: Device calibrated as specified in 
9.4.1 and used to measure sample flow rate at the monitoring site.
    7.1.8 Membrane particle filter: A membrane filter of 0.8 to 2 <greek 
mu<ls-thn-eq>m porosity is used to protect the flow controller from 
particles during long-term sampling. This item is optional for short-
term sampling.
    7.1.9 Vacuum pump: A vacuum pump equipped with a vacuum gauge and 
capable of maintaining at least 70 kPa (0.7 atm) vacuum differential 
across the flow control device at the specified flow rate is required 
for sampling.
    7.1.10 Temperature control device: The temperature of the absorbing 
solution during sampling must be maintained at 15 deg. +\10  deg.C. As 
soon as possible following sampling and until analysis, the temperature 
of the collected sample must be maintained at 5 deg. +\5  deg.C. Where 
an extended period of time may elapse before the collected sample can be 
moved to the lower storage temperature, a collection temperature near 
the lower limit of the 15 +\ 10  deg.C range should be used to minimize 
losses during this period. Thermoelectric coolers specifically designed 
for this temperature control are available commercially and normally 
operate in the range of 5 deg. to 15  deg.C. Small refrigerators can be 
modified to provide the required temperature control; however, inlet 
lines must be insulated from the lower temperatures to prevent 
condensation when sampling under humid conditions. A small heating pad 
may be necessary when sampling at low temperatures (<ls-thn-eq>7  deg.C) 
to prevent the absorbing solution from freezing.(17)
    7.1.11 Sampling train container: The absorbing solution must be 
shielded from light during and after sampling. Most commercially 
available sampler trains are enclosed in a light-proof box.
    7.1.12 Timer: A timer is recommended to initiate and to stop 
sampling for the 24-hour period. The timer is not a required piece of 
equipment; however, without the timer a technician would be required to 
start and stop the sampling manually. An elapsed time meter is also 
recommended to determine the duration of the sampling period.
    7.2 Shipping.
    7.2.1 Shipping container: A shipping container that can maintain a 
temperature of 5 deg. +\5  deg.C is used for transporting the sample 
from the collection site to the analytical laboratory. Ice coolers or 
refrigerated shipping containers have been found to be satisfactory. The 
use of eutectic cold packs instead of ice will give a more stable 
temperature control. Such equipment is available from Cole-Parmer 
Company, 7425 North Oak Park Avenue, Chicago, IL 60648.
    7.3 Analysis.
    7.3.1 Spectrophotometer: A spectrophotometer suitable for 
measurement of absorbances at 548 nm with an effective spectral 
bandwidth of less than 15 nm is required for analysis. If the 
spectrophotometer reads out in transmittance, convert to absorbance as 
follows:
[GRAPHIC] [TIFF OMITTED] TC08NO91.000

where:

A = absorbance, and
T = transmittance (0<<ls-thn-eq>/=T<1).

    A standard wavelength filter traceable to the National Bureau of 
Standards is used to verify the wavelength calibration according to the 
procedure enclosed with the filter. The wavelength calibration must be 
verified upon initial receipt of the instrument and after each 160 hours 
of normal use or every 6 months, whichever occurs first.
    7.3.2 Spectrophotometer cells: A set of 1-cm path length cells 
suitable for use in the visible region is used during analysis. If the 
cells are unmatched, a matching correction factor must be determined 
according to Section 10.1.
    7.3.3 Temperature control device: The color development step during 
analysis must be conducted in an environment that is in the range of 
20 deg. to 30  deg.C and controlled to +\1  deg.C. Both calibration and 
sample analysis must be performed under identical conditions (within 1 
deg.C). Adequate temperature control may be obtained by means of 
constant temperature baths, water baths with manual temperature control, 
or temperature controlled rooms.
    7.3.4 Glassware: Class A volumetric glassware of various capacities 
is required for preparing and standardizing reagents and standards and 
for dispensing solutions during analysis. These included pipets, 
volumetric flasks, and burets.
    7.3.5 TCM waste receptacle: A glass waste receptacle is required for 
the storage of spent TCM solution. This vessel should be stoppered and 
stored in a hood at all times.
    8.0 Reagents.
    8.1 Sampling.

[[Page 14]]

    8.1.1 Distilled water: Purity of distilled water must be verified by 
the following procedure:(18)
<bullet<ls-thn-eq> Place 0.20 mL of potassium permanganate solution 
(0.316 g/L), 500 mL of distilled water, and 1mL of concentrated sulfuric 
acid in a chemically resistant glass bottle, stopper the bottle, and 
allow to stand.
<bullet<ls-thn-eq> If the permanganate color (pink) does not disappear 
completely after a period of 1 hour at room temperature, the water is 
suitable for use.
<bullet<ls-thn-eq> If the permanganate color does disappear, the water 
can be purified by redistilling with one crystal each of barium 
hydroxide and potassium permanganate in an all glass still.

    8.1.2 Absorbing reagent (0.04 M potassium tetrachloromercurate 
[TCM]): Dissolve 10.86 g mercuric chloride, 0.066 g EDTA, and 6.0 g 
potassium chloride in distilled water and dilute to volume with 
distilled water in a 1,000-mL volumetric flask. (Caution: Mercuric 
chloride is highly poisonous. If spilled on skin, flush with water 
immediately.) The pH of this reagent should be between 3.0 and 5.0 (10) 
Check the pH of the absorbing solution by using pH indicating paper or a 
pH meter. If the pH of the solution is not between 3.0 and 5.0, dispose 
of the solution according to one of the disposal techniques described in 
Section 13.0. The absorbing reagent is normally stable for 6 months. If 
a precipitate forms, dispose of the reagent according to one of the 
procedures described in Section 13.0.
    8.2 Analysis.
    8.2.1 Sulfamic acid (0.6%): Dissolve 0.6 g sulfamic acid in 100 mL 
distilled water. Perpare fresh daily.
    8.2.2 Formaldehyde (0.2%): Dilute 5 mL formaldehyde solution (36 to 
38 percent) to 1,000 mL with distilled water. Prepare fresh daily.
    8.2.3 Stock iodine solution (0.1 N): Place 12.7 g resublimed iodine 
in a 250-mL beaker and add 40 g potassium iodide and 25 mL water. Stir 
until dissolved, transfer to a 1,000 mL volumetric flask and dilute to 
volume with distilled water.
    8.2.4 Iodine solution (0.01 N): Prepare approximately 0.01 N iodine 
solution by diluting 50 mL of stock iodine solution (Section 8.2.3) to 
500 mL with distilled water.
    8.2.5 Starch indicator solution: Triturate 0.4 g soluble starch and 
0.002 g mercuric iodide (preservative) with enough distilled water to 
form a paste. Add the paste slowly to 200 mL of boiling distilled water 
and continue boiling until clear. Cool and transfer the solution to a 
glass stopperd bottle.
    8.2.6 1 N hydrochloric acid: Slowly and while stirring, add 86 mL of 
concentrated hydrochloric acid to 500 mL of distilled water. Allow to 
cool and dilute to 1,000 mL with distilled water.
    8.2.7 Potassium iodate solution: Accurately weigh to the nearest 0.1 
mg, 1.5 g (record weight) of primary standard grade potassium iodate 
that has been previously dried at 180  deg.C for at least 3 hours and 
cooled in a dessicator. Dissolve, then dilute to volume in a 500-mL 
volumetric flask with distilled water.
    8.2.8 Stock sodium thiosulfate solution (0.1 N): Prepare a stock 
solution by dissolving 25 g sodium thiosulfate (Na<INF>2</INF> 
S<INF>2</INF> O<INF>3</INF>/5H<INF>2</INF> O) in 1,000 mL freshly 
boiled, cooled, distilled water and adding 0.1 g sodium carbonate to the 
solution. Allow the solution to stand at least 1 day before 
standardizing. To standardize, accurately pipet 50 mL of potassium 
iodate solution (Section 8.2.7) into a 500-mL iodine flask and add 2.0 g 
of potassium iodide and 10 mL of 1 N HCl. Stopper the flask and allow to 
stand for 5 minutes. Titrate the solution with stock sodium thiosulfate 
solution (Section 8.2.8) to a pale yellow color. Add 5 mL of starch 
solution (Section 8.2.5) and titrate until the blue color just 
disappears. Calculate the normality (N<INF>s</INF>) of the stock sodium 
thiosulfate solution as follows:
[GRAPHIC] [TIFF OMITTED] TC08NO91.001

where:

M = volume of thiosulfate required in mL, and
W = weight of potassium iodate in g (recorded weight in Section 8.2.7).
[GRAPHIC] [TIFF OMITTED] TC08NO91.002

    8.2.9  Working sodium thiosulfate titrant (0.01 N): Accurately pipet 
100 mL of stock sodium thiosulfate solution (Section 8.2.8) into a 
1,000-mL volumetric flask and dilute to volume with freshly boiled, 
cooled, distilled water. Calculate the normality of the working sodium 
thiosulfate titrant (N<INF>T</INF>) as follows:
[GRAPHIC] [TIFF OMITTED] TC08NO91.003

    8.2.10 Standardized sulfite solution for the preparation of working 
sulfite-TCM solution: Dissolve 0.30 g sodium metabisulfite (Na<INF>2</INF> 
S<INF>2</INF> O<INF>5</INF>) or 0.40 g sodium sulfite (Na<INF>2</INF> 
SO<INF>3</INF>) in 500 mL of recently boiled, cooled, distilled water. 
(Sulfite solution is unstable; it is therefore important to use water of 
the highest purity to minimize this instability.) This solution contains 
the equivalent of 320 to 400 <greek mu<ls-thn-eq>g SO<INF>2</INF>/mL. 
The actual concentration of the solution is determined by adding excess 
iodine and back-titrating with standard sodium thiosulfate solution. To 
back-titrate, pipet 50 mL of the 0.01 N iodine solution (Section 8.2.4) 
into each of two 500-mL iodine flasks (A and B). To flask A (blank) add 
25 mL distilled water, and to flask B (sample)

[[Page 15]]

pipet 25 mL sulfite solution. Stopper the flasks and allow to stand for 
5 minutes. Prepare the working sulfite-TCM solution (Section 8.2.11) 
immediately prior to adding the iodine solution to the flasks. Using a 
buret containing standardized 0.01 N thiosulfate titrant (Section 
8.2.9), titrate the solution in each flask to a pale yellow color. Then 
add 5 mL starch solution (Section 8.2.5) and continue the titration 
until the blue color just disappears.
    8.2.11 Working sulfite-TCM solution: Accurately pipet 5 mL of the 
standard sulfite solution (Section 8.2.10) into a 250-mL volumetric 
flask and dilute to volume with 0.04 M TCM. Calculate the concentration 
of sulfur dioxide in the working solution as follows:
[GRAPHIC] [TIFF OMITTED] TC08NO91.004

where:

A = volume of thiosulfate titrant required for the blank, mL;
B = volume of thiosulfate titrant required for the sample, mL;
N<INF>T</INF> = normality of the thiosulfate titrant, from equation (3);
32,000 = milliequivalent weight of SO<INF>2,</INF> <greek 
mu<ls-thn-eq>g;
25 = volume of standard sulfite solution, mL; and
0.02 = dilution factor.

    This solution is stable for 30 days if kept at 5  deg.C. (16) If not 
kept at 5  deg.C, prepare fresh daily.
    8.2.12 Purified pararosaniline (PRA) stock solution (0.2% nominal):
    8.2.12.1 Dye specifications--

<bullet<ls-thn-eq> The dye must have a maximum absorbance at a 
wavelength of 540 nm when assayed in a buffered solution of 0.1 M sodium 
acetate-acetic acid;
<bullet<ls-thn-eq> The absorbance of the reagent blank, which is 
temperature sensitive (0.015 absorbance unit/  deg.C), must not exceed 
0.170 at 22  deg.C with a 1-cm optical path length when the blank is 
prepared according to the specified procedure;
<bullet<ls-thn-eq> The calibration curve (Section 10.0) must have a 
slope equal to 0.030+\0.002 absorbance unit/<greek mu<ls-thn-eq>g 
SO<INF>2</INF> with a 1-cm optical path length when the dye is pure and 
the sulfite solution is properly standardized.

    8.2.12.2 Preparation of stock PRA solution-- A specially purified 
(99 to 100 percent pure) solution of pararosaniline, which meets the 
above specifications, is commercially available in the required 0.20 
percent concentration (Harleco Co.). Alternatively, the dye may be 
purified, a stock solution prepared, and then assayed according to the 
procedure as described below.(10)
    8.2.12.3 Purification procedure for PRA--
    1. Place 100 mL each of 1-butanol and 1 N HCl in a large separatory 
funnel (250-mL) and allow to equilibrate. Note: Certain batches of 1-
butanol contain oxidants that create an SO<INF>2</INF> demand. Before 
using, check by placing 20 mL of 1-butanol and 5 mL of 20 percent 
potassium iodide (KI) solution in a 50-mL separatory funnel and shake 
thoroughly. If a yellow color appears in the alcohol phase, redistill 
the 1-butanol from silver oxide and collect the middle fraction or 
purchase a new supply of 1-butanol.
    2. Weigh 100 mg of pararosaniline hydrochloride dye (PRA) in a small 
beaker. Add 50 mL of the equilibrated acid (drain in acid from the 
bottom of the separatory funnel in 1.) to the beaker and let stand for 
several minutes. Discard the remaining acid phase in the separatory 
funnel.
    3. To a 125-mL separatory funnel, add 50 mL of the equilibrated 1-
butanol (draw the 1-butanol from the top of the separatory funnel in 
1.). Transfer the acid solution (from 2.) containing the dye to the 
funnel and shake carefully to extract. The violet impurity will transfer 
to the organic phase.
    4. Transfer the lower aqueous phase into another separatory funnel, 
add 20 mL of equilibrated 1-butanol, and extract again.
    5. Repeat the extraction procedure with three more 10-mL portions of 
equilibrated 1-butanol.
    6. After the final extraction, filter the acid phase through a 
cotton plug into a 50-mL volumetric flask and bring to volume with 1 N 
HCl. This stock reagent will be a yellowish red.
    7. To check the purity of the PRA, perform the assay and adjustment 
of concentration (Section 8.2.12.4) and prepare a reagent blank (Section 
11.2); the absorbance of this reagent blank at 540 nm should be less 
than 0.170 at 22  deg.C. If the absorbance is greater than 0.170 under 
these conditions, further extractions should be performed.
    8.2.12.4 PRA assay procedure-- The concentration of pararosaniline 
hydrochloride (PRA) need be assayed only once after purification. It is 
also recommended that commercial solutions of pararosaniline be assayed 
when first purchased. The assay procedure is as follows:(10)
    1. Prepare 1 M acetate-acetic acid buffer stock solution with a pH 
of 4.79 by dissolving

[[Page 16]]

13.61 g of sodium acetate trihydrate in distilled water in a 100-mL 
volumetric flask. Add 5.70 mL of glacial acetic acid and dilute to 
volume with distilled water.
    2. Pipet 1 mL of the stock PRA solution obtained from the 
purification process or from a commercial source into a 100-mL 
volumetric flask and dilute to volume with distilled water.
    3. Transfer a 5-mL aliquot of the diluted PRA solution from 2. into 
a 50-mL volumetric flask. Add 5mL of 1 M acetate-acetic acid buffer 
solution from 1. and dilute the mixture to volume with distilled water. 
Let the mixture stand for 1 hour.
    4. Measure the absorbance of the above solution at 540 nm with a 
spectrophotometer against a distilled water reference. Compute the 
percentage of nominal concentration of PRA by
[GRAPHIC] [TIFF OMITTED] TC08NO91.005

where:

A = measured absorbance of the final mixture (absorbance units);
W = weight in grams of the PRA dye used in the assay to prepare 50 mL of 
stock solution (for example, 0.100 g of dye was used to prepare 50 mL of 
solution in the purification procedure; when obtained from commercial 
sources, use the stated concentration to compute W; for 98% PRA, W=.098 
g.); and
K = 21.3 for spectrophotometers having a spectral bandwidth of less than 
15 nm and a path length of 1 cm.

    8.2.13 Pararosaniline reagent: To a 250-mL volumetric flask, add 20 
mL of stock PRA solution. Add an additional 0.2 mL of stock solution for 
each percentage that the stock assays below 100 percent. Then add 25 mL 
of 3 M phosphoric acid and dilute to volume with distilled water. The 
reagent is stable for at least 9 months. Store away from heat and light.
    9.0 Sampling Procedure.
    9.1 General Considerations. Procedures are described for short-term 
sampling (30-minute and 1-hour) and for long-term sampling (24-hour). 
Different combinations of absorbing reagent volume, sampling rate, and 
sampling time can be selected to meet special needs. For combinations 
other than those specifically described, the conditions must be adjusted 
so that linearity is maintained between absorbance and concentration 
over the dynamic range. Absorbing reagent volumes less than 10 mL are 
not recommended. The collection efficiency is above 98 percent for the 
conditions described; however, the efficiency may be substantially lower 
when sampling concentrations below 25<greek mu<ls-thn-eq><greek 
gamma<ls-thn-eq>SO<INF>2</INF>/m\3\.(8,9)
    9.2 30-Minute and 1-Hour Sampling. Place 10 mL of TCM absorbing 
reagent in a midget impinger and seal the impinger with a thin film of 
silicon stopcock grease (around the ground glass joint). Insert the 
sealed impinger into the sampling train as shown in Figure 1, making 
sure that all connections between the various components are leak tight. 
Greaseless ball joint fittings, heat shrinkable 
Teflon<SUP><register mark<ls-thn-eq></SUP> tubing, or 
Teflon<SUP><register mark<ls-thn-eq></SUP> tube fittings may be used to 
attain leakfree conditions for portions of the sampling train that come 
into contact with air containing SO<INF>2.</INF> Shield the absorbing 
reagent from direct sunlight by covering the impinger with aluminum foil 
or by enclosing the sampling train in a light-proof box. Determine the 
flow rate according to Section 9.4.2. Collect the sample at 1+\0.10 L/
min for 30-minute sampling or 0.500+\0.05 L/min for 1-hour sampling. 
Record the exact sampling time in minutes, as the sample volume will 
later be determined using the sampling flow rate and the sampling time. 
Record the atmospheric pressure and temperature.
    9.3 24-Hour Sampling. Place 50 mL of TCM absorbing solution in a 
large absorber, close the cap, and, if needed, apply the heat shrink 
material as shown in Figure 3. Verify that the reagent level is at the 
50 mL mark on the absorber. Insert the sealed absorber into the sampling 
train as shown in Figure 2. At this time verify that the absorber 
temperature is controlled to 15+\10  deg.C. During sampling, the 
absorber temperature must be controlled to prevent decomposition of the 
collected complex. From the onset of sampling until analysis, the 
absorbing solution must be protected from direct sunlight. Determine the 
flow rate according to Section 9.4.2. Collect the sample for 24 hours 
from midnight to midnight at a flow rate of 0.200+\0.020 L/min. A start/
stop timer is helpful for initiating and stopping sampling and an 
elapsed time meter will be useful for determining the sampling time.

[[Page 17]]

<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

    9.4 Flow Measurement.
    9.4.1 Calibration: Flow measuring devices used for the on-site flow 
measurements required in 9.4.2 must be calibrated against a reliable 
flow or volume standard such as an NBS traceable bubble flowmeter or 
calibrated wet test meter. Rotameters or critical orifices used in the 
sampling train may be calibrated, if desired, as a quality control 
check, but such calibration shall not replace the on-site flow 
measurements required by 9.4.2. In-line rotameters, if they are to be 
calibrated, should be calibrated in situ, with the appropriate volume of 
solution in the absorber.
    9.4.2 Determination of flow rate at sampling site: For short-term 
samples, the standard flow rate is determined at the sampling site at 
the initiation and completion of sample collection with a calibrated 
flow measuring device connected to the inlet of the absorber. For 24-
hour samples, the standard flow rate is determined at the time the 
absorber is placed in the sampling train and again when the absorber is 
removed from the train for shipment to the analytical laboratory with a 
calibrated flow measuring device connected to the inlet of the sampling 
train. The flow rate determination must be made with all components of 
the sampling system in operation (e.g., the absorber temperature 
controller and any sample box heaters must also be operating). Equation 
6 may be used to determine the standard flow rate when a calibrated 
positive displacement meter is used as the flow measuring device. Other 
types of calibrated flow measuring devices may also be used to determine 
the flow rate at the sampling site provided that the user applies any 
appropriate corrections to devices for which output is dependent on 
temperature or pressure.

[[Page 18]]

[GRAPHIC] [TIFF OMITTED] TC08NO91.006

where:

Q<INF>std</INF> = flow rate at standard conditions, std L/min (25  deg.C 
and 760 mm Hg);
Q<INF>act</INF> = flow rate at monitoring site conditions, L/min;
P<INF>b</INF> = barometric pressure at monitoring site conditions, mm Hg 
or kPa;
RH = fractional relative humidity of the air being measured;
P<INF>H</INF>2<INF>O</INF> = vapor pressure of water at the temperature 
of the air in the flow or volume standard, in the same units as 
P<INF>b,</INF> (for wet volume standards only, i.e., bubble flowmeter or 
wet test meter; for dry standards, i.e., dry test meter, 
P<INF>H</INF>2<INF>O</INF>=0);
P<INF>std</INF> = standard barometric pressure, in the same units as 
P<INF>b</INF> (760 mm Hg or 101 kPa); and
T<INF>meter</INF> = temperature of the air in the flow or volume 
standard,  deg.C (e.g., bubble flowmeter).

    If a barometer is not available, the following equation may be used 
to determine the barometric pressure:
[GRAPHIC] [TIFF OMITTED] TC08NO91.007

where:

H = sampling site elevation above sea level in meters.

    If the initial flow rate (Q<INF>i</INF>) differs from the flow rate 
of the critical orifice or the flow rate indicated by the flowmeter in 
the sampling train (Q<INF>c</INF>) by more than 5 percent as determined 
by equation (8), check for leaks and redetermine Q<INF>i</INF>.
[GRAPHIC] [TIFF OMITTED] TC08NO91.008

    Invalidate the sample if the difference between the initial 
(Q<INF>i</INF>) and final (Q<INF>f</INF>) flow rates is more than 5 
percent as determined by equation (9):
[GRAPHIC] [TIFF OMITTED] TC08NO91.009

    9.5 Sample Storage and Shipment. Remove the impinger or absorber 
from the sampling train and stopper immediately. Verify that the 
temperature of the absorber is not above 25  deg.C. Mark the level of 
the solution with a temporary (e.g., grease pencil) mark. If the sample 
will not be analyzed within 12 hours of sampling, it must be stored at 
5 deg. +\5  deg.C until analysis. Analysis must occur within 30 days. If 
the sample is transported or shipped for a period exceeding 12 hours, it 
is recommended that thermal coolers using eutectic ice packs, 
refrigerated shipping containers, etc., be used for periods up to 48 
hours. (17) Measure the temperature of the absorber solution when the 
shipment is received. Invalidate the sample if the temperature is above 
10  deg.C. Store the sample at 5 deg. +\5  deg.C until it is analyzed.
    10.0 Analytical Calibration.
    10.1 Spectrophotometer Cell Matching. If unmatched spectrophotometer 
cells are used, an absorbance correction factor must be determined as 
follows:
    1. Fill all cells with distilled water and designate the one that 
has the lowest absorbance at 548 nm as the reference. (This reference 
cell should be marked as such and continually used for this purpose 
throughout all future analyses.)
    2. Zero the spectrophotometer with the reference cell.
    3. Determine the absorbance of the remaining cells (A<INF>c</INF>) 
in relation to the reference cell and record these values for future 
use. Mark all cells in a manner that adequately identifies the 
correction.
    The corrected absorbance during future analyses using each cell is 
determining as follows:
[GRAPHIC] [TIFF OMITTED] TC08NO91.010

where:

A = corrected absorbance,
A<INF>obs</INF> = uncorrected absorbance, and
A<INF>c</INF> = cell correction.

    10.2 Static Calibration Procedure (Option 1). Prepare a dilute 
working sulfite-TCM solution by diluting 10 mL of the working sulfite-
TCM solution (Section 8.2.11) to 100 mL with TCM absorbing reagent. 
Following the table below, accurately pipet the indicated volumes of the 
sulfite-TCM solutions into a series of 25-mL volumetric flasks. Add TCM 
absorbing reagent as indicated to bring the volume in each flask to 10 
mL.

[[Page 19]]

------------------------------------------------------------------------
                                    Volume of
                                     sulfite-  Volume of   Total <greek
       Sulfite-TCM solution            TCM      TCM, mL   mu<ls-thn-eq>g
                                     solution              SO<INF>2</INF> (approx.*
------------------------------------------------------------------------
Working...........................        4.0        6.0          28.8
Working...........................        3.0        7.0          21.6
Working...........................        2.0        8.0          14.4
Dilute working....................       10.0        0.0           7.2
Dilute working....................        5.0        5.0           3.6
                                          0.0       10.0           0.0
------------------------------------------------------------------------
*Based on working sulfite-TCM solution concentration of 7.2 <greek mu<ls-
  thn-eq>g SO<INF>2</INF>/mL; the actual total <greek mu>g SO<INF>2</INF> must be calculated
  using equation 11 below.

    To each volumetric flask, add 1 mL 0.6% sulfamic acid (Section 
8.2.1), accurately pipet 2 mL 0.2% formaldehyde solution (Section 
8.2.2), then add 5 mL pararosaniline solution (Section 8.2.13). Start a 
laboratory timer that has been set for 30 minutes. Bring all flasks to 
volume with recently boiled and cooled distilled water and mix 
thoroughly. The color must be developed (during the 30-minute period) in 
a temperature environment in the range of 20 deg. to 30  deg.C, which is 
controlled to <SUP>+</SUP>\1  deg.C. For increased precision, a constant 
temperature bath is recommended during the color development step. After 
30 minutes, determine the corrected absorbance of each standard at 548 
nm against a distilled water reference (Section 10.1). Denote this 
absorbance as (A). Distilled water is used in the reference cell rather 
than the reagant blank because of the temperature sensitivity of the 
reagent blank. Calculate the total micrograms SO<INF>2</INF> in each 
solution:
[GRAPHIC] [TIFF OMITTED] TC08NO91.011

where:

V<INF>TCM/SO</INF>2 = volume of sulfite-TCM solution used, mL;
C<INF>TCM/SO</INF>2 = concentration of sulfur dioxide in the working 
sulfite-TCM, <greek mu<ls-thn-eq>g SO<INF>2</INF>/mL (from equation 4); 
and
D = dilution factor (D = 1 for the working sulfite-TCM solution; D = 0.1 
for the diluted working sulfite-TCM solution).

    A calibration equation is determined using the method of linear 
least squares (Section 12.1). The total micrograms SO<INF>2</INF> 
contained in each solution is the x variable, and the corrected 
absorbance (eq. 10) associated with each solution is the y variable. For 
the calibration to be valid, the slope must be in the range of 0.030 
<SUP>+</SUP>\0.002 absorbance unit/<greek mu<ls-thn-eq>g SO<INF>2,</INF> 
the intercept as determined by the least squares method must be equal to 
or less than 0.170 absorbance unit when the color is developed at 22 
deg.C (add 0.015 to this 0.170 specification for each  deg.C above 22 
deg.C) and the correlation coefficient must be greater than 0.998. If 
these criteria are not met, it may be the result of an impure dye and/or 
an improperly standardized sulfite-TCM solution. A calibration factor 
(B<INF>s</INF>) is determined by calculating the reciprocal of the slope 
and is subsequently used for calculating the sample concentration 
(Section 12.3).
    10.3 Dynamic Calibration Procedures (Option 2). Atmospheres 
containing accurately known concentrations of sulfur dioxide are 
prepared using permeation devices. In the systems for generating these 
atmospheres, the permeation device emits gaseous SO<INF>2</INF> at a 
known, low, constant rate, provided the temperature of the device is 
held constant (<SUP>+</SUP>\0.1  deg.C) and the device has been 
accurately calibrated at the temperature of use. The SO<INF>2</INF> 
permeating from the device is carried by a low flow of dry carrier gas 
to a mixing chamber where it is diluted with SO<INF>2</INF>-free air to 
the desired concentration and supplied to a vented manifold. A typical 
system is shown schematically in Figure 4 and this system and other 
similar systems have been described in detail by O'Keeffe and Ortman; 
(19) Scaringelli, Frey, and Saltzman, (20) and Scaringelli, O'Keeffe, 
Rosenberg, and Bell. (21) Permeation devices may be prepared or 
purchased and in both cases must be traceable either to a National 
Bureau of Standards (NBS) Standard Reference Material (SRM 1625, SRM 
1626, SRM 1627) or to an NBS/EPA-approved commercially available 
Certified Reference Material (CRM). CRM's are described in Reference 22, 
and a list of CRM sources is available from the address shown for 
Reference 22. A recommended protocol for certifying a permeation device 
to an NBS SRM or CRM is given in Section 2.0.7 of Reference 2. Device 
permeation rates of 0.2 to 0.4 <greek mu<ls-thn-eq>g/min, inert gas 
flows of about 50 mL/min, and dilution air flow rates from 1.1 to 15 L/
min conveniently yield standard atmospheres in the range of 25 to 600 
<greek mu<ls-thn-eq>g SO<INF>2</INF>/m\3\ (0.010 to 0.230 ppm).
    10.3.1 Calibration Option 2A (30-minute and 1-hour samples): 
Generate a series of six standard atmospheres of SO<INF>2</INF> (e.g., 
0, 50, 100, 200, 350, 500, 750 <greek mu<ls-thn-eq>g/m\3\) by adjusting 
the dilution flow rates appropriately. The concentration of SO<INF>2</INF> 
in each atmosphere is calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.014

where:

[[Page 20]]

C<INF>a</INF> = concentration of SO<INF>2</INF> at standard conditions, 
<greek mu<ls-thn-eq>g/m\3\;
P<INF>r</INF> = permeation rate, <greek mu<ls-thn-eq>g/min;
Q<INF>d</INF> = flow rate of dilution air, std L/min; and
Q<INF>p</INF> = flow rate of carrier gas across permeation device, std 
L/min.
<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

[[Page 21]]

    Be sure that the total flow rate of the standard exceeds the flow 
demand of the sample train, with the excess flow vented at atmospheric 
pressure. Sample each atmosphere using similar apparatus as shown in 
Figure 1 and under the same conditions as field sampling (i.e., use same 
absorbing reagent volume and sample same volume of air at an equivalent 
flow rate). Due to the length of the sampling periods required, this 
method is not recommended for 24-hour sampling. At the completion of 
sampling, quantitatively transfer the contents of each impinger to one 
of a series of 25-mL volumetric flasks (if 10 mL of absorbing solution 
was used) using small amounts of distilled water for rinse (<5mL). If 
<ls-thn-eq>10 mL of absorbing solution was used, bring the absorber 
solution in each impinger to orginal volume with distilled H<INF>2</INF> 
O and pipet 10-mL portions from each impinger into a series of 25-mL 
volumetric flasks. If the color development steps are not to be started 
within 12 hours of sampling, store the solutions at 5 deg. +\ 5  deg.C. 
Calculate the total micrograms SO<INF>2</INF> in each solution as 
follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.015

where:

C<INF>a</INF> = concentration of SO<INF>2</INF> in the standard 
atmosphere, <greek mu<ls-thn-eq>g/m\3\ ;
O<INF>s</INF> = sampling flow rate, std L/min;
t=sampling time, min;
V<INF>a</INF> = volume of absorbing solution used for color development 
(10 mL); and
V<INF>b</INF> = volume of absorbing solution used for sampling, mL.

    Add the remaining reagents for color development in the same manner 
as in Section 10.2 for static solutions. Calculate a calibration 
equation and a calibration factor (B<INF>g</INF>) according to Section 
10.2, adhering to all the specified criteria.
    10.3.2 Calibration Option 2B (24-hour samples): Generate a standard 
atmosphere containing approximately 1,050 <greek mu<ls-thn-eq>g 
SO<INF>2</INF>/m\3\ and calculate the exact concentration according to 
equation 12. Set up a series of six absorbers according to Figure 2 and 
connect to a common manifold for sampling the standard atmosphere. Be 
sure that the total flow rate of the standard exceeds the flow demand at 
the sample manifold, with the excess flow vented at atmospheric 
pressure. The absorbers are then allowed to sample the atmosphere for 
varying time periods to yield solutions containing 0, 0.2, 0.6, 1.0, 
1.4, 1.8, and 2.2 <greek mu<ls-thn-eq>g SO<INF>2</INF>/mL solution. The 
sampling times required to attain these solution concentrations are 
calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.016

where:

t = sampling time, min;
V<INF>b</INF> = volume of absorbing solution used for sampling (50 mL);
C<INF>s</INF> = desired concentration of SO<INF>2</INF> in the absorbing 
solution, <greek mu<ls-thn-eq>g/mL;
C<INF>a</INF> = concentration of the standard atmosphere calculated 
according to equation 12, <greek mu<ls-thn-eq>g/m\3\ ; and
Q<INF>s</INF> = sampling flow rate, std L/min.

    At the completion of sampling, bring the absorber solutions to 
original volume with distilled water. Pipet a 10-mL portion from each 
absorber into one of a series of 25-mL volumetric flasks. If the color 
development steps are not to be started within 12 hours of sampling, 
store the solutions at 5 deg. +\ 5  deg.C. Add the remaining reagents 
for color development in the same manner as in Section 10.2 for static 
solutions. Calculate the total <greek mu<ls-thn-eq>g SO<INF>2</INF> in 
each standard as follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.017

where:

V<INF>a</INF> = volume of absorbing solution used for color development 
(10 mL).
All other parameters are defined in equation 14.

    Calculate a calibration equation and a calibration factor 
(B<INF>t</INF>) according to Section 10.2 adhering to all the specified 
criteria.
    11.0 Sample Preparation and Analysis.
    11.1 Sample Preparation. Remove the samples from the shipping 
container. If the shipment period exceeded 12 hours from the completion 
of sampling, verify that the temperature is below 10  deg.C. Also, 
compare the solution level to the temporary level mark on the absorber. 
If either the temperature is above 10  deg.C or there was significant 
loss (more than 10 mL) of the sample during shipping, make an 
appropriate notation in the record and invalidate the sample. Prepare 
the samples for analysis as follows:
    1. For 30-minute or 1-hour samples: Quantitatively transfer the 
entire 10 mL amount of absorbing solution to a 25-mL volumetric flask 
and rinse with a small amount (<5 mL) of distilled water.
    2. For 24-hour samples: If the volume of the sample is less than the 
original 50-mL volume (permanent mark on the absorber), adjust the 
volume back to the original volume with distilled water to compensate 
for water lost to evaporation during sampling. If the final volume is 
greater than the original volume, the volume must be measured using a 
graduated cylinder. To analyze, pipet 10 mL

[[Page 22]]

of the solution into a 25-mL volumetric flask.
    11.2 Sample Analysis. For each set of determinations, prepare a 
reagent blank by adding 10 mL TCM absorbing solution to a 25-mL 
volumetric flask, and two control standards containing approximately 5 
and 15 <greek mu<ls-thn-eq>g SO<INF>2,</INF> respectively. The control 
standards are prepared according to Section 10.2 or 10.3. The analysis 
is carried out as follows:
    1. Allow the sample to stand 20 minutes after the completion of 
sampling to allow any ozone to decompose (if applicable).
    2. To each 25-mL volumetric flask containing reagent blank, sample, 
or control standard, add 1 mL of 0.6% sulfamic acid (Section 8.2.1) and 
allow to react for 10 min.
    3. Accurately pipet 2 mL of 0.2% formaldehyde solution (Section 
8.2.2) and then 5 mL of pararosaniline solution (Section 8.2.13) into 
each flask. Start a laboratory timer set at 30 minutes.
    4. Bring each flask to volume with recently boiled and cooled 
distilled water and mix thoroughly.
    5. During the 30 minutes, the solutions must be in a temperature 
controlled environment in the range of 20 deg. to 30  deg.C maintained 
to <SUP>+</SUP>\ 1  deg.C. This temperature must also be within 1  deg.C 
of that used during calibration.
    6. After 30 minutes and before 60 minutes, determine the corrected 
absorbances (equation 10) of each solution at 548 nm using 1-cm optical 
path length cells against a distilled water reference (Section 10.1). 
(Distilled water is used as a reference instead of the reagent blank 
because of the sensitivity of the reagent blank to temperature.)
    7. Do not allow the colored solution to stand in the cells because a 
film may be deposited. Clean the cells with isopropyl alcohol after use.
    8. The reagent blank must be within 0.03 absorbance units of the 
intercept of the calibration equation determined in Section 10.
    11.3 Absorbance range. If the absorbance of the sample solution 
ranges between 1.0 and 2.0, the sample can be diluted 1:1 with a portion 
of the reagent blank and the absorbance redetermined within 5 minutes. 
Solutions with higher absorbances can be diluted up to sixfold with the 
reagent blank in order to obtain scale readings of less than 1.0 
absorbance unit. However, it is recommended that a smaller portion (<10 
mL) of the original sample be reanalyzed (if possible) if the sample 
requires a dilution greater than 1:1.
    11.4 Reaqent disposal. All reagents containing mercury compounds 
must be stored and disposed of using one of the procedures contained in 
Section 13. Until disposal, the discarded solutions can be stored in 
closed glass containers and should be left in a fume hood.
    12.0 Calculations.
    12.1 Calibration Slope, Intercept, and Correlation Coefficient. The 
method of least squares is used to calculate a calibration equation in 
the form of:
[GRAPHIC] [TIFF OMITTED] TC08NO91.012

where:

y = corrected absorbance,
m = slope, absorbance unit/<greek mu<ls-thn-eq>g SO<INF>2,</INF>
x = micrograms of SO<INF>2,</INF>
b = y intercept (absorbance units).

    The slope (m), intercept (b), and correlation coefficient (r) are 
calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.018

[GRAPHIC] [TIFF OMITTED] TR31AU93.019

[GRAPHIC] [TIFF OMITTED] TR31AU93.020

where n is the number of calibration points.
    A data form (Figure 5) is supplied for easily organizing calibration 
data when the slope, intercept, and correlation coefficient are 
calculated by hand.
    12.2 Total Sample Volume. Determine the sampling volume at standard 
conditions as follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.021

where:

V<INF>std</INF> = sampling volume in std L,
Q<INF>i</INF> = standard flow rate determined at the initiation of 
sampling in std L/min,
Q<INF>f</INF> = standard flow rate determined at the completion of 
sampling is std L/min, and
t = total sampling time, min.

    12.3 Sulfur Dioxide Concentration. Calculate and report the 
concentration of each sample as follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.022

where:

A = corrected absorbance of the sample solution, from equation (10);
A<INF>o</INF> = corrected absorbance of the reagent blank, using 
equation (10);
B<INF>x</INF> = calibration factor equal to B<INF>s,</INF> 
B<INF>g,</INF> or B<INF>t</INF> depending on the calibration procedure 
used, the reciprocal of the slope of the calibration equation;
V<INF>a</INF> = volume of absorber solution analyzed, mL;
V<INF>b</INF> = total volume of solution in absorber (see 11.1-2), mL; 
and
V<INF>std</INF> = standard air volume sampled, std L (from Section 
12.2).

[[Page 23]]

                                                    Data Form
                                             [For hand calculations]
----------------------------------------------------------------------------------------------------------------
                                                      Absor- bance
     Calibration point no.       Micro- grams So<INF>2</INF>        units
----------------------------------------------------------------------------------------------------------------
                                       (x)                (y)                 x<SUP>2</SUP>                xy           y<SUP>2</SUP>
1.............................  .................  .................  .................  ................  .....
2.............................  .................  .................  .................  ................  .....
3.............................  .................  .................  .................  ................  .....
4.............................  .................  .................  .................  ................  .....
5.............................  .................  .................  .................  ................  .....
6.............................  .................  .................  .................  ................  .....
----------------------------------------------------------------------------------------------------------------

<greek sigma<ls-thn-eq> x=------  <greek sigma<ls-thn-eq> y=------  
<greek sigma<ls-thn-eq> x\2\=------  <greek sigma<ls-thn-eq>xy------  
<greek sigma<ls-thn-eq>y\2\------  
n=------ (number of pairs of coordinates.)
________________________________________________________________________

Figure 5. Data form for hand calculations.

    12.4 Control Standards. Calculate the analyzed micrograms of 
SO<INF>2</INF> in each control standard as follows:
[GRAPHIC] [TIFF OMITTED] TC08NO91.070

where:

C<INF>q</INF> = analyzed <greek mu<ls-thn-eq>g SO<INF>2</INF> in each 
control standard,
A = corrected absorbance of the control standard, and
A<INF>o</INF> = corrected absorbance of the reagent blank.

    The difference between the true and analyzed values of the control 
standards must not be greater than 1 <greek mu<ls-thn-eq>g. If the 
difference is greater than 1 <greek mu<ls-thn-eq>g, the source of the 
discrepancy must be identified and corrected.
    12.5 Conversion of <greek mu<ls-thn-eq>g/m\3\ to ppm (v/v). If 
desired, the concentration of sulfur dioxide at reference conditions can 
be converted to ppm SO<INF>2</INF> (v/v) as follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.023

    13.0 The TCM absorbing solution and any reagents containing mercury 
compounds must be treated and disposed of by one of the methods 
discussed below. Both methods remove greater than 99.99 percent of the 
mercury.
    13.1 Disposal of Mercury-Containing Solutions.
    13.2 Method for Forming an Amalgam.
    1. Place the waste solution in an uncapped vessel in a hood.
    2. For each liter of waste solution, add approximately 10 g of 
sodium carbonate until neutralization has occurred (NaOH may have to be 
used).
    3. Following neutralization, add 10 g of granular zinc or magnesium.
    4. Stir the solution in a hood for 24 hours. Caution must be 
exercised as hydrogen gas is evolved by this treatment process.
    5. After 24 hours, allow the solution to stand without stirring to 
allow the mercury amalgam (solid black material) to settle to the bottom 
of the waste receptacle.
    6. Upon settling, decant and discard the supernatant liquid.
    7. Quantitatively transfer the solid material to a container and 
allow to dry.
    8. The solid material can be sent to a mercury reclaiming plant. It 
must not be discarded.
    13.3 Method Using Aluminum Foil Strips.
    1. Place the waste solution in an uncapped vessel in a hood.
    2. For each liter of waste solution, add approximately 10 g of 
aluminum foil strips. If all the aluminum is consumed and no gas is 
evolved, add an additional 10 g of foil. Repeat until the foil is no 
longer consumed and allow the gas to evolve for 24 hours.
    3. Decant the supernatant liquid and discard.
    4. Transfer the elemental mercury that has settled to the bottom of 
the vessel to a storage container.
    5. The mercury can be sent to a mercury reclaiming plant. It must 
not be discarded.
    14.0 References for SO<INF>2</INF> Method.
    1. Quality Assurance Handbook for Air Pollution Measurement Systems, 
Volume I, Principles. EPA-600/9-76-005, U.S. Environmental Protection 
Agency, Research Triangle Park, NC 27711, 1976.
    2. Quality Assurance Handbook for Air Pollution Measurement Systems, 
Volume II, Ambient Air Specific Methods. EPA-600/4-77-027a, U.S. 
Environmental Protection Agency, Research Triangle Park, NC 27711, 1977.
    3. Dasqupta, P. K., and K. B. DeCesare. Stability of Sulfur Dioxide 
in Formaldehyde and Its Anomalous Behavior in Tetrachloromercurate (II). 
Submitted for publication in Atmospheric Environment, 1982.
    4. West, P. W., and G. C. Gaeke. Fixation of Sulfur Dioxide as 
Disulfitomercurate (II) and Subsequent Colorimetric Estimation. Anal. 
Chem., 28:1816, 1956.
    5. Ephraim, F. Inorganic Chemistry. P. C. L. Thorne and E. R. 
Roberts, Eds., 5th Edition, Interscience, 1948, p. 562.
    6. Lyles, G. R., F. B. Dowling, and V. J. Blanchard. Quantitative 
Determination of Formaldehyde in the Parts Per Hundred Million 
Concentration Level. J. Air. Poll. Cont. Assoc., Vol. 15(106), 1965.
    7. McKee, H. C., R. E. Childers, and O. Saenz, Jr. Collaborative 
Study of Reference Method for Determination of Sulfur Dioxide in the 
Atmosphere (Pararosaniline Method). EPA-APTD-0903, U.S. Environmental 
Protection Agency, Research Triangle Park, NC 27711, September 1971.
    8. Urone, P., J. B. Evans, and C. M. Noyes. Tracer Techniques in 
Sulfur--Air Pollution Studies Apparatus and Studies of Sulfur Dioxide 
Colorimetric and Conductometric Methods. Anal. Chem., 37: 1104, 1965.

[[Page 24]]

    9. Bostrom, C. E. The Absorption of Sulfur Dioxide at Low 
Concentrations (pphm) Studied by an Isotopic Tracer Method. Intern. J. 
Air Water Poll., 9:333, 1965.
    10. Scaringelli, F. P., B. E. Saltzman, and S. A. Frey. 
Spectrophotometric Determination of Atmospheric Sulfur Dioxide. Anal. 
Chem., 39: 1709, 1967.
    11. Pate, J. B., B. E. Ammons, G. A. Swanson, and J. P. Lodge, Jr. 
Nitrite Interference in Spectrophotometric Determination of Atmospheric 
Sulfur Dioxide. Anal. Chem., 37:942, 1965.
    12. Zurlo, N., and A. M. Griffini. Measurement of the Sulfur Dioxide 
Content of the Air in the Presence of Oxides of Nitrogen and Heavy 
Metals. Medicina Lavoro, 53:330, 1962.
    13. Rehme, K. A., and F. P. Scaringelli. Effect of Ammonia on the 
Spectrophotometric Determination of Atmospheric Concentrations of Sulfur 
Dioxide. Anal. Chem., 47:2474, 1975.
    14. McCoy, R. A., D. E. Camann, and H. C. McKee. Collaborative Study 
of Reference Method for Determination of Sulfur Dioxide in the 
Atmosphere (Pararosaniline Method) (24-Hour Sampling). EPA-650/4-74-027, 
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, 
December 1973.
    15. Fuerst, R. G. Improved Temperature Stability of Sulfur Dioxide 
Samples Collected by the Federal Reference Method. EPA-600/4-78-018, 
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, 
April 1978.
    16. Scaringelli, F. P., L. Elfers, D. Norris, and S. Hochheiser. 
Enhanced Stability of Sulfur Dioxide in Solution. Anal. Chem., 42:1818, 
1970.
    17. Martin, B. E. Sulfur Dioxide Bubbler Temperature Study. EPA-600/
4-77-040, U.S. Environmental Protection Agency, Research Triangle Park, 
NC 27711, August 1977.
    18. American Society for Testing and Materials. ASTM Standards, 
Water; Atmospheric Analysis. Part 23. Philadelphia, PA, October 1968, p. 
226.
    19. O'Keeffe, A. E., and G. C. Ortman. Primary Standards for Trace 
Gas Analysis. Anal. Chem., 38:760, 1966.
    20. Scaringelli, F. P., S. A. Frey, and B. E. Saltzman. Evaluation 
of Teflon Permeation Tubes for Use with Sulfur Dioxide. Amer. Ind. 
Hygiene Assoc. J., 28:260, 1967.
    21. Scaringelli, F. P., A. E. O'Keeffe, E. Rosenberg, and J. P. 
Bell, Preparation of Known Concentrations of Gases and Vapors With 
Permeation Devices Calibrated Gravimetrically. Anal. Chem., 42:871, 
1970.
    22. A Procedure for Establishing Traceability of Gas Mixtures to 
Certain National Bureau of Standards Standard Reference Materials. EPA-
600/7-81-010, U.S. Environmental Protection Agency, Environmental 
Monitoring Systems Laboratory (MD-77), Research Triangle Park, NC 27711, 
January 1981.

[47 FR 54899, Dec. 6, 1982; 48 FR 17355, Apr. 22, 1983]

    Appendix B to Part 50--Reference Method for the Determination of 
   Suspended Particulate Matter in the Atmosphere (High-Volume Method)

    1.0 Applicability.
    1.1 This method provides a measurement of the mass concentration of 
total suspended particulate matter (TSP) in ambient air for determining 
compliance with the primary and secondary national ambient air quality 
standards for particulate matter as specified in Sec. 50.6 and Sec. 50.7 
of this chapter. The measurement process is nondestructive, and the size 
of the sample collected is usually adequate for subsequent chemical 
analysis. Quality assurance procedures and guidance are provided in part 
58, appendixes A and B, of this chapter and in References 1 and 2.
    2.0 Principle.
    2.1 An air sampler, properly located at the measurement site, draws 
a measured quantity of ambient air into a covered housing and through a 
filter during a 24-hr (nominal) sampling period. The sampler flow rate 
and the geometry of the shelter favor the collection of particles up to 
25-50 <greek mu<ls-thn-eq>m (aerodynamic diameter), depending on wind 
speed and direction.(3) The filters used are specified to have a minimum 
collection efficiency of 99 percent for 0.3 <greek mu<ls-thn-eq>m (DOP) 
particles (see Section 7.1.4).
    2.2 The filter is weighed (after moisture equilibration) before and 
after use to determine the net weight (mass) gain. The total volume of 
air sampled, corrected to EPA standard conditions (25  deg.C, 760 mm Hg 
[101 kPa]), is determined from the measured flow rate and the sampling 
time. The concentration of total suspended particulate matter in the 
ambient air is computed as the mass of collected particles divided by 
the volume of air sampled, corrected to standard conditions, and is 
expressed in micrograms per standard cubic meter (<greek mu<ls-thn-eq>g/
std m\3\). For samples collected at temperatures and pressures 
significantly different than standard conditions, these corrected 
concentrations may differ substantially from actual concentrations 
(micrograms per actual cubic meter), particularly at high elevations. 
The actual particulate matter concentration can be calculated from the 
corrected concentration using the actual temperature and pressure during 
the sampling period.
    3.0 Range.
    3.1 The approximate concentration range of the method is 2 to 750 
<greek mu<ls-thn-eq>g/std m<SUP>3.</SUP> The upper limit is determined 
by the point at which the sampler can no longer maintain the specified

[[Page 25]]

flow rate due to the increased pressure drop of the loaded filter. This 
point is affected by particle size distribution, moisture content of the 
collected particles, and variability from filter to filter, among other 
things. The lower limit is determined by the sensitivity of the balance 
(see Section 7.10) and by inherent sources of error (see Section 6).
    3.2 At wind speeds between 1.3 and 4.5 m/sec (3 and 10 mph), the 
high-volume air sampler has been found to collect particles up to 25 to 
50 <greek mu<ls-thn-eq>m, depending on wind speed and direction.(3) For 
the filter specified in Section 7.1, there is effectively no lower limit 
on the particle size collected.
    4.0 Precision.
    4.1 Based upon collaborative testing, the relative standard 
deviation (coefficient of variation) for single analyst precision 
(repeatability) of the method is 3.0 percent. The corresponding value 
for interlaboratory precision (reproducibility) is 3.7 percent.(4)
    5.0 Accuracy.
    5.1 The absolute accuracy of the method is undefined because of the 
complex nature of atmospheric particulate matter and the difficulty in 
determining the ``true'' particulate matter concentration. This method 
provides a measure of particulate matter concentration suitable for the 
purpose specified under Section 1.0, Applicability.
    6.0 Inherent Sources of Error.
    6.1 Airflow variation. The weight of material collected on the 
filter represents the (integrated) sum of the product of the 
instantaneous flow rate times the instantaneous particle concentration. 
Therefore, dividing this weight by the average flow rate over the 
sampling period yields the true particulate matter concentration only 
when the flow rate is constant over the period. The error resulting from 
a nonconstant flow rate depends on the magnitude of the instantaneous 
changes in the flow rate and in the particulate matter concentration. 
Normally, such errors are not large, but they can be greatly reduced by 
equipping the sampler with an automatic flow controlling mechanism that 
maintains constant flow during the sampling period. Use of a contant 
flow controller is recommended.*
---------------------------------------------------------------------------

    *At elevated altitudes, the effectiveness of automatic flow 
controllers may be reduced because of a reduction in the maximum sampler 
flow.
---------------------------------------------------------------------------

    6.2 Air volume measurement. If the flow rate changes substantially 
or nonuniformly during the sampling period, appreciable error in the 
estimated air volume may result from using the average of the 
presampling and postsampling flow rates. Greater air volume measurement 
accuracy may be achieved by (1) equipping the sampler with a flow 
controlling mechanism that maintains constant air flow during the 
sampling period,* (2) using a calibrated, continuous flow rate recording 
device to record the actual flow rate during the samping period and 
integrating the flow rate over the period, or (3) any other means that 
will accurately measure the total air volume sampled during the sampling 
period. Use of a continuous flow recorder is recommended, particularly 
if the sampler is not equipped with a constant flow controller.
    6.3 Loss of volatiles. Volatile particles collected on the filter 
may be lost during subsequent sampling or during shipment and/or storage 
of the filter prior to the postsampling weighing.(5) Although such 
losses are largely unavoidable, the filter should be reweighed as soon 
after sampling as practical.
    6.4 Artifact particulate matter. Artifact particulate matter can be 
formed on the surface of alkaline glass fiber filters by oxidation of 
acid gases in the sample air, resulting in a higher than true TSP 
determination.(6 7) This effect usually occurs early in the sample 
period and is a function of the filter pH and the presence of acid 
gases. It is generally believed to account for only a small percentage 
of the filter weight gain, but the effect may become more significant 
where relatively small particulate weights are collected.
    6.5 Humidity. Glass fiber filters are comparatively insensitive to 
changes in relative humidity, but collected particulate matter can be 
hygroscopic.(8) The moisture conditioning procedure minimizes but may 
not completely eliminate error due to moisture.
    6.6 Filter handling. Careful handling of the filter between the 
presampling and postsampling weighings is necessary to avoid errors due 
to loss of fibers or particles from the filter. A filter paper cartridge 
or cassette used to protect the filter can minimize handling errors. 
(See Reference 2, Section 2).
    6.7 Nonsampled particulate matter. Particulate matter may be 
deposited on the filter by wind during periods when the sampler is 
inoperative. (9) It is recommended that errors from this source be 
minimized by an automatic mechanical device that keeps the filter 
covered during nonsampling periods, or by timely installation and 
retrieval of filters to minimize the nonsampling periods prior to and 
following operation.
    6.8 Timing errors. Samplers are normally controlled by clock timers 
set to start and stop the sampler at midnight. Errors in the nominal 
1,440-min sampling period may result from a power interruption during 
the sampling period or from a discrepancy between the start or stop time 
recorded on the filter information record and the actual start or stop 
time of the sampler. Such discrepancies may be caused by (1) poor 
resolution of the timer set-points, (2) timer error due to power 
interruption, (3) missetting of

[[Page 26]]

the timer, or (4) timer malfunction. In general, digital electronic 
timers have much better set-point resolution than mechanical timers, but 
require a battery backup system to maintain continuity of operation 
after a power interruption. A continuous flow recorder or elapsed time 
meter provides an indication of the sampler run-time, as well as 
indication of any power interruption during the sampling period and is 
therefore recommended.
    6.9 Recirculation of sampler exhaust. Under stagnant wind 
conditions, sampler exhaust air can be resampled. This effect does not 
appear to affect the TSP measurement substantially, but may result in 
increased carbon and copper in the collected sample. (10) This problem 
can be reduced by ducting the exhaust air well away, preferably 
downwind, from the sampler.
    7.0 Apparatus.
    (See References 1 and 2 for quality assurance information.)
    Note: Samplers purchased prior to the effective date of this 
amendment are not subject to specifications preceded by 
(<dagger<ls-thn-eq>).
    7.1 Filter. (Filters supplied by the Environmental Protection Agency 
can be assumed to meet the following criteria. Additional specifications 
are required if the sample is to be analyzed chemically.)
    7.1.1 Size: 20.3 +\ 0.2 x 25.4 +\ 0.2 cm (nominal 8 x 10 in).
    7.1.2 Nominal exposed area: 406.5 cm\2\ (63 in\2\).
    7.1.3. Material: Glass fiber or other relatively inert, 
nonhygroscopic material. (8)
    7.1.4 Collection efficiency: 99 percent minimum as measured by the 
DOP test (ASTM-2986) for particles of 0.3 <greek mu<ls-thn-eq>m 
diameter.
    7.1.5 Recommended pressure drop range: 42-54 mm Hg (5.6-7.2 kPa) at 
a flow rate of 1.5 std m\3\/min through the nominal exposed area.
    7.1.6 pH: 6 to 10. (11)
    7.1.7 Integrity: 2.4 mg maximum weight loss. (11)
    7.1.8 Pinholes: None.
    7.1.9 Tear strength: 500 g minimum for 20 mm wide strip cut from 
filter in weakest dimension. (See ASTM Test D828-60).
    7.1.10 Brittleness: No cracks or material separations after single 
lengthwise crease.
    7.2 Sampler. The air sampler shall provide means for drawing the air 
sample, via reduced pressure, through the filter at a uniform face 
velocity.
    7.2.1 The sampler shall have suitable means to:
    a. Hold and seal the filter to the sampler housing.
    b. Allow the filter to be changed conveniently.
    c. Preclude leaks that would cause error in the measurement of the 
air volume passing through the filter.
    d. (<dagger<ls-thn-eq>) Manually adjust the flow rate to accommodate 
variations in filter pressure drop and site line voltage and altitude. 
The adjustment may be accomplished by an automatic flow controller or by 
a manual flow adjustment device. Any manual adjustment device must be 
designed with positive detents or other means to avoid unintentional 
changes in the setting.
---------------------------------------------------------------------------

    (<dagger<ls-thn-eq>) See note at beginning of Section 7 of this 
appendix.
---------------------------------------------------------------------------

    7.2.2 Minimum sample flow rate, heavily loaded filter: 1.1 m\3\/min 
(39 ft\3\/min).<dagger<ls-thn-eq>
---------------------------------------------------------------------------

    <dagger<ls-thn-eq> These specifications are in actual air volume 
units; to convert to EPA standard air volume units, multiply the 
specifications by (P<INF>b</INF>/P<INF>std</INF>)(298/T) where 
P<INF>b</INF> and T are the barometric pressure in mm Hg (or kPa) and 
the temperature in K at the sampler, and P<INF>std</INF> is 760 mm Hg 
(or 101 kPa).
---------------------------------------------------------------------------

    7.2.3 Maximum sample flow rate, clean filter: 1.7 m\3\/min (60 
ft\3\/min).<dagger<ls-thn-eq>
    7.2.4 Blower Motor: The motor must be capable of continuous 
operation for 24-hr periods.
    7.3 Sampler shelter.
    7.3.1 The sampler shelter shall:
    a. Maintain the filter in a horizontal position at least 1 m above 
the sampler supporting surface so that sample air is drawn downward 
through the filter.
    b. Be rectangular in shape with a gabled roof, similar to the design 
shown in Figure 1.
    c. Cover and protect the filter and sampler from precipitation and 
other weather.
    d. Discharge exhaust air at least 40 cm from the sample air inlet.
    e. Be designed to minimize the collection of dust from the 
supporting surface by incorporating a baffle between the exhaust outlet 
and the supporting surface.
    7.3.2 The sampler cover or roof shall overhang the sampler housing 
somewhat, as shown in Figure 1, and shall be mounted so as to form an 
air inlet gap between the cover and the sampler housing walls. 
<SUP><dagger<ls-thn-eq></SUP> This sample air inlet should be 
approximately uniform on all sides of the sampler. 
<SUP><dagger<ls-thn-eq></SUP> The area of the sample air inlet must be 
sized to provide an effective particle capture air velocity of between 
20 and 35 cm/sec at the recommended operational flow rate. The capture 
velocity is the sample air flow rate divided by the inlet area measured 
in a horizontal plane at the lower edge of the cover. 
<SUP><dagger<ls-thn-eq></SUP> Ideally, the inlet area and operational 
flow rate should be selected to obtain a capture air velocity of 25 +\2 
cm/sec.
    7.4 Flow rate measurement devices.
    7.4.1 The sampler shall incorporate a flow rate measurement device 
capable of indicating the total sampler flow rate. Two common types of 
flow indicators covered in the calibration procedure are (1) an 
electronic mass flowmeter and (2) an orifice or orifices

[[Page 27]]

located in the sample air stream together with a suitable pressure 
indicator such as a manometer, or aneroid pressure gauge. A pressure 
recorder may be used with an orifice to provide a continuous record of 
the flow. Other types of flow indicators (including rotameters) having 
comparable precision and accuracy are also acceptable.
    7.4.2 <dagger<ls-thn-eq> The flow rate measurement device must be 
capable of being calibrated and read in units corresponding to a flow 
rate which is readable to the nearest 0.02 std m\3\/min over the range 
1.0 to 1.8 std m\3\/min.
    7.5 Thermometer, to indicate the approximate air temperature at the 
flow rate measurement orifice, when temperature corrections are used.
    7.5.1 Range: -40 deg. to +50  deg.C (223-323 K).
    7.5.2 Resolution: 2  deg.C (2 K).
    7.6 Barometer, to indicate barometric pressure at the flow rate 
measurement orifice, when pressure corrections are used.
    7.6.1 Range: 500 to 800 mm Hg (66-106 kPa).
    7.6.2 Resolution: +\5 mm Hg (0.67 kPa).
    7.7 Timing/control device.
    7.7.1 The timing device must be capable of starting and stopping the 
sampler to obtain an elapsed run-time of 24 hr +\1 hr (1,440 +\60 min).
    7.7.2 Accuracy of time setting: +\30 min, or better. (See Section 
6.8).
    7.8 Flow rate transfer standard, traceable to a primary standard. 
(See Section 9.2.)
    7.8.1 Approximate range: 1.0 to 1.8 m\3\/min.
    7.8.2 Resolution: 0.02 m\3\/min.
    7.8.3 Reproducibility: +\2 percent (2 times coefficient of 
variation) over normal ranges of ambient temperature and pressure for 
the stated flow rate range. (See Reference 2, Section 2.)
    7.8.4 Maximum pressure drop at 1.7 std m\3\/min; 50 cm H2 O (5 kPa).
    7.8.5 The flow rate transfer standard must connect without leaks to 
the inlet of the sampler and measure the flow rate of the total air 
sample.
    7.8.6 The flow rate transfer standard must include a means to vary 
the sampler flow rate over the range of 1.0 to 1.8 m\3\/min (35-64 
ft\3\/min) by introducing various levels of flow resistance between the 
sampler and the transfer standard inlet.
    7.8.7 The conventional type of flow transfer standard consists of: 
An orifice unit with adapter that connects to the inlet of the sampler, 
a manometer or other device to measure orifice pressure drop, a means to 
vary the flow through the sampler unit, a thermometer to measure the 
ambient temperature, and a barometer to measure ambient pressure. Two 
such devices are shown in Figures 2a and 2b. Figure 2a shows multiple 
fixed resistance plates, which necessitate disassembly of the unit each 
time the flow resistance is changed. A preferable design, illustrated in 
Figure 2b, has a variable flow restriction that can be adjusted 
externally without disassembly of the unit. Use of a conventional, 
orifice-type transfer standard is assumed in the calibration procedure 
(Section 9). However, the use of other types of transfer standards 
meeting the above specifications, such as the one shown in Figure 2c, 
may be approved; see the note following Section 9.1.
    7.9 Filter conditioning environment
    7.9.1 Controlled temperature: between 15 deg. and 30  deg.C with 
less than <SUP>+</SUP>\3  deg.C variation during equilibration period.
    7.9.2 Controlled humidity: Less than 50 percent relative humidity, 
constant within <SUP>+</SUP>\5 percent.
    7.10 Analytical balance.
    7.10.1 Sensitivity: 0.1 mg.
    7.10.2 Weighing chamber designed to accept an unfolded 20.3 x 25.4 
cm (8 x 10 in) filter.
    7.11 Area light source, similar to X-ray film viewer, to backlight 
filters for visual inspection.
    7.12 Numbering device, capable of printing identification numbers on 
the filters before they are placed in the filter conditioning 
environment, if not numbered by the supplier.
    8.0 Procedure.
    (See References 1 and 2 for quality assurance information.)
    8.1 Number each filter, if not already numbered, near its edge with 
a unique identification number.
    8.2 Backlight each filter and inspect for pinholes, particles, and 
other imperfections; filters with visible imperfections must not be 
used.
    8.3 Equilibrate each filter in the conditioning environment for at 
least 24-hr.
    8.4 Following equilibration, weigh each filter to the nearest 
milligram and record this tare weight (W<INF>i</INF>) with the filter 
identification number.
    8.5 Do not bend or fold the filter before collection of the sample.
    8.6 Open the shelter and install a numbered, preweighed filter in 
the sampler, following the sampler manufacturer's instructions. During 
inclement weather, precautions must be taken while changing filters to 
prevent damage to the clean filter and loss of sample from or damage to 
the exposed filter. Filter cassettes that can be loaded and unloaded in 
the laboratory may be used to minimize this problem (See Section 6.6).
    8.7 Close the shelter and run the sampler for at least 5 min to 
establish run-temperature conditions.
    8.8 Record the flow indicator reading and, if needed, the barometric 
pressure (P <INF>3</INF>) and the ambient temperature (T <INF>3</INF>) 
see NOTE following step 8.12). Stop the sampler. Determine the sampler 
flow rate (see Section 10.1); if it is outside the acceptable range (1.1 
to 1.7 m\3\/min [39-60 ft\3\/min]), use a different filter, or adjust 
the sampler flow rate. Warning: Substantial flow adjustments may affect 
the

[[Page 28]]

calibration of the orifice-type flow indicators and may necessitate 
recalibration.
    8.9 Record the sampler identification information (filter number, 
site location or identification number, sample date, and starting time).
    8.10 Set the timer to start and stop the sampler such that the 
sampler runs 24-hrs, from midnight to midnight (local time).
    8.11 As soon as practical following the sampling period, run the 
sampler for at least 5 min to again establish run-temperature 
conditions.
    8.12 Record the flow indicator reading and, if needed, the 
barometric pressure (P <INF>3</INF>) and the ambient temperature (T 
<INF>3</INF>).
    Note: No onsite pressure or temperature measurements are necessary 
if the sampler flow indicator does not require pressure or temperature 
corrections (e.g., a mass flowmeter) or if average barometric pressure 
and seasonal average temperature for the site are incorporated into the 
sampler calibration (see step 9.3.9). For individual pressure and 
temperature corrections, the ambient pressure and temperature can be 
obtained by onsite measurements or from a nearby weather station. 
Barometric pressure readings obtained from airports must be station 
pressure, not corrected to sea level, and may need to be corrected for 
differences in elevation between the sampler site and the airport. For 
samplers having flow recorders but not constant flow controllers, the 
average temperature and pressure at the site during the sampling period 
should be estimated from weather bureau or other available data.
    8.13 Stop the sampler and carefully remove the filter, following the 
sampler manufacturer's instructions. Touch only the outer edges of the 
filter. See the precautions in step 8.6.
    8.14 Fold the filter in half lengthwise so that only surfaces with 
collected particulate matter are in contact and place it in the filter 
holder (glassine envelope or manila folder).
    8.15 Record the ending time or elapsed time on the filter 
information record, either from the stop set-point time, from an elapsed 
time indicator, or from a continuous flow record. The sample period must 
be 1,440 +\ 60 min. for a valid sample.
    8.16 Record on the filter information record any other factors, such 
as meteorological conditions, construction activity, fires or dust 
storms, etc., that might be pertinent to the measurement. If the sample 
is known to be defective, void it at this time.
    8.17 Equilibrate the exposed filter in the conditioning environment 
for at least 24-hrs.
    8.18 Immediately after equilibration, reweigh the filter to the 
nearest milligram and record the gross weight with the filter 
identification number. See Section 10 for TSP concentration 
calculations.
    9.0 Calibration.
    9.1 Calibration of the high volume sampler's flow indicating or 
control device is necessary to establish traceability of the field 
measurement to a primary standard via a flow rate transfer standard. 
Figure 3a illustrates the certification of the flow rate transfer 
standard and Figure 3b illustrates its use in calibrating a sampler flow 
indicator. Determination of the corrected flow rate from the sampler 
flow indicator, illustrated in Figure 3c, is addressed in Section 10.1
    Note: The following calibration procedure applies to a conventional 
orifice-type flow transfer standard and an orifice-type flow indicator 
in the sampler (the most common types). For samplers using a pressure 
recorder having a square-root scale, 3 other acceptable calibration 
procedures are provided in Reference 12. Other types of transfer 
standards may be used if the manufacturer or user provides an 
appropriately modified calibration procedure that has been approved by 
EPA under Section 2.8 of appendix C to part 58 of this chapter.
    9.2 Certification of the flow rate transfer standard.
    9.2.1 Equipment required: Positive displacement standard volume 
meter traceable to the National Bureau of Standards (such as a Roots 
meter or equivalent), stop-watch, manometer, thermometer, and barometer.
    9.2.2 Connect the flow rate transfer standard to the inlet of the 
standard volume meter. Connect the manometer to measure the pressure at 
the inlet of the standard volume meter. Connect the orifice manometer to 
the pressure tap on the transfer standard. Connect a high-volume air 
pump (such as a high-volume sampler blower) to the outlet side of the 
standard volume meter. See Figure 3a.
    9.2.3 Check for leaks by temporarily clamping both manometer lines 
(to avoid fluid loss) and blocking the orifice with a large-diameter 
rubber stopper, wide cellophane tape, or other suitable means. Start the 
high-volume air pump and note any change in the standard volume meter 
reading. The reading should remain constant. If the reading changes, 
locate any leaks by listening for a whistling sound and/or retightening 
all connections, making sure that all gaskets are properly installed.
    9.2.4 After satisfactorily completing the leak check as described 
above, unclamp both manometer lines and zero both manometers.
    9.2.5 Achieve the appropriate flow rate through the system, either 
by means of the variable flow resistance in the transfer standard or by 
varying the voltage to the air pump. (Use of resistance plates as shown 
in Figure 1a is discouraged because the above leak check must be 
repeated each time a new resistance plate is installed.) At least five 
different but constant flow rates, evenly distributed, with at least 
three in the specified

[[Page 29]]

flow rate interval (1.1 to 1.7 m\3\/min [39-60 ft \3\/min]), are 
required.
    9.2.6 Measure and record the certification data on a form similar to 
the one illustrated in Figure 4 according to the following steps.
    9.2.7 Observe the barometric pressure and record as P<INF>1</INF> 
(item 8 in Figure 4).
    9.2.8 Read the ambient temperature in the vicinity of the standard 
volume meter and record it as T<INF>1</INF> (item 9 in Figure 4).
    9.2.9 Start the blower motor, adjust the flow, and allow the system 
to run for at least 1 min for a constant motor speed to be attained.
    9.2.10 Observe the standard volume meter reading and simultaneously 
start a stopwatch. Record the initial meter reading (V<INF>i</INF>) in 
column 1 of Figure 4.
    9.2.11 Maintain this constant flow rate until at least 3 m\3\ of air 
have passed through the standard volume meter. Record the standard 
volume meter inlet pressure manometer reading as <greek 
delta<ls-thn-eq>P (column 5 in Figure 4), and the orifice manometer 
reading as <greek delta<ls-thn-eq>H (column 7 in Figure 4). Be sure to 
indicate the correct units of measurement.
    9.2.12 After at least 3 m\3\ of air have passed through the system, 
observe the standard volume meter reading while simultaneously stopping 
the stopwatch. Record the final meter reading (V<INF>f</INF>) in column 
2 and the elapsed time (t) in column 3 of Figure 4.
    9.2.13 Calculate the volume measured by the standard volume meter at 
meter conditions of temperature and pressures as 
V<INF>m</INF>=V<INF>f</INF>-V<INF>i.</INF> Record in column 4 of Figure 
4.
    9.2.14 Correct this volume to standard volume (std m\3\) as follows:
    [GRAPHIC] [TIFF OMITTED] TR31AU93.024
    
where:

V<INF>std</INF> = standard volume, std m\3\;
V<INF>m</INF> = actual volume measured by the standard volume meter;
P<INF>1</INF> = barometric pressure during calibration, mm Hg or kPa;
<greek delta<ls-thn-eq>P = differential pressure at inlet to volume 
meter, mm Hg or kPa;
P<INF>std</INF> = 760 mm Hg or 101 kPa;
T<INF>std</INF> = 298 K;
T<INF>1</INF> = ambient temperature during calibration, K.
Calculate the standard flow rate (std m\3\/min) as follows:
[GRAPHIC] [TIFF OMITTED] TC08NO91.013

where:

Q<INF>std</INF> = standard volumetric flow rate, std m\3\/min
t = elapsed time, minutes.

    Record Q<INF>std</INF> to the nearest 0.01 std m\3\/min in column 6 
of Figure 4.
    9.2.15 Repeat steps 9.2.9 through 9.2.14 for at least four 
additional constant flow rates, evenly spaced over the approximate range 
of 1.0 to 1.8 std m\3\/min (35-64 ft\3\/min).
    9.2.16 For each flow, compute

<greek delta<ls-thn-eq><greek delta<ls-thn-eq>H (P<INF>1</INF>/
P<INF>std</INF>)(298/T<INF>1</INF>)

(column 7a of Figure 4) and plot these value against Q<INF>std</INF> as 
shown in Figure 3a. Be sure to use consistent units (mm Hg or kPa) for 
barometric pressure. Draw the orifice transfer standard certification 
curve or calculate the linear least squares slope (m) and intercept (b) 
of the certification curve:

<greek delta<ls-thn-eq><greek delta<ls-thn-eq>H (P<INF>1</INF>/
P<INF>std</INF>)(298/T<INF>1</INF>)

=mQ<INF>std</INF>+b. See Figures 3 and 4. A certification graph should 
be readable to 0.02 std m\3\/min.
    9.2.17 Recalibrate the transfer standard annually or as required by 
applicable quality control procedures. (See Reference 2.)
    9.3 Calibration of sampler flow indicator.

    Note: For samplers equipped with a flow controlling device, the flow 
controller must be disabled to allow flow changes during calibration of 
the sampler's flow indicator, or the alternate calibration of the flow 
controller given in 9.4 may be used. For samplers using an orifice-type 
flow indicator downstream of the motor, do not vary the flow rate by 
adjusting the voltage or power supplied to the sampler.

    9.3.1 A form similar to the one illustrated in Figure 5 should be 
used to record the calibration data.
    9.3.2 Connect the transfer standard to the inlet of the sampler. 
Connect the orifice manometer to the orifice pressure tap, as 
illustrated in Figure 3b. Make sure there are no leaks between the 
orifice unit and the sampler.
    9.3.3 Operate the sampler for at least 5 minutes to establish 
thermal equilibrium prior to the calibration.
    9.3.4 Measure and record the ambient temperature, T<INF>2,</INF> and 
the barometric pressure, P<INF>2,</INF> during calibration.
    9.3.5 Adjust the variable resistance or, if applicable, insert the 
appropriate resistance plate (or no plate) to achieve the desired flow 
rate.
    9.3.6 Let the sampler run for at least 2 min to re-establish the 
run-temperature conditions. Read and record the pressure drop across the 
orifice (<greek delta<ls-thn-eq>H) and the sampler flow rate indication 
(I) in the appropriate columns of Figure 5.
    9.3.7 Calculate <greek delta<ls-thn-eq><greek 
delta<ls-thn-eq>H(P<INF>2</INF>/P<INF>std</INF>)(298/T<INF>2</INF>) and 
determine the flow rate at standard conditions (Q<INF>std</INF>) either 
graphically from the certification curve or by calculating Q<INF>std</INF> 
from the least square slope and intercept of the transfer standard's 
transposed certification curve: Q<INF>std</INF>=1/m <greek 
delta<ls-thn-eq>H(P<INF>2</INF>/P<INF>std</INF>)(298/T<INF>2</INF>)-b. 
Record the value of Q<INF>std</INF> on Figure 5.

[[Page 30]]

    9.3.8 Repeat steps 9.3.5, 9.3.6, and 9.3.7 for several additional 
flow rates distributed over a range that includes 1.1 to 1.7 std m\3\/
min.
    9.3.9 Determine the calibration curve by plotting values of the 
appropriate expression involving I, selected from table 1, against 
Q<INF>std.</INF> The choice of expression from table 1 depends on the 
flow rate measurement device used (see Section 7.4.1) and also on 
whether the calibration curve is to incorporate geographic average 
barometric pressure (P<INF>a</INF>) and seasonal average temperature 
(T<INF>a</INF>) for the site to approximate actual pressure and 
temperature. Where P<INF>a</INF> and T<INF>a</INF> can be determined for 
a site for a seasonal period such that the actual barometric pressure 
and temperature at the site do not vary by more than +\60 mm Hg (8 kPa) 
from P<INF>a</INF> or +\15  deg.C from T<INF>a,</INF> respectively, then 
using P<INF>a</INF> and T<INF>a</INF> avoids the need for subsequent 
pressure and temperature calculation when the sampler is used. The 
geographic average barometric pressure (P<INF>a</INF>) may be estimated 
from an altitude-pressure table or by making an (approximate) elevation 
correction of -26 mm Hg (-3.46 kPa) for each 305 m (1,000 ft) above sea 
level (760 mm Hg or 101 kPa). The seasonal average temperature 
(T<INF>a</INF>) may be estimated from weather station or other records. 
Be sure to use consistent units (mm Hg or kPa) for barometric pressure.
    9.3.10 Draw the sampler calibration curve or calculate the linear 
least squares slope (m), intercept (b), and correlation coefficient of 
the calibration curve: [Expression from table 1]= mQ<INF>std</INF>+b. 
See Figures 3 and 5. Calibration curves should be readable to 0.02 std 
m\3\/min.
    9.3.11 For a sampler equipped with a flow controller, the flow 
controlling mechanism should be re-enabled and set to a flow near the 
lower flow limit to allow maximum control range. The sample flow rate 
should be verified at this time with a clean filter installed. Then add 
two or more filters to the sampler to see if the flow controller 
maintains a constant flow; this is particularly important at high 
altitudes where the range of the flow controller may be reduced.
    9.4 Alternate calibration of flow-controlled samplers. A flow-
controlled sampler may be calibrated solely at its controlled flow rate, 
provided that previous operating history of the sampler demonstrates 
that the flow rate is stable and reliable. In this case, the flow 
indicator may remain uncalibrated but should be used to indicate any 
relative change between initial and final flows, and the sampler should 
be recalibrated more often to minimize potential loss of samples because 
of controller malfunction.
    9.4.1 Set the flow controller for a flow near the lower limit of the 
flow range to allow maximum control range.
    9.4.2 Install a clean filter in the sampler and carry out steps 
9.3.2, 9.3.3, 9.3.4, 9.3.6, and 9.3.7.
    9.4.3 Following calibration, add one or two additional clean filters 
to the sampler, reconnect the transfer standard, and operate the sampler 
to verify that the controller maintains the same calibrated flow rate; 
this is particularly important at high altitudes where the flow control 
range may be reduced.
<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

[[Page 31]]

<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

    10.0 Calculations of TSP Concentration.
    10.1 Determine the average sampler flow rate during the sampling 
period according to either 10.1.1 or 10.1.2 below.
    10.1.1 For a sampler without a continuous flow recorder, determine 
the appropriate expression to be used from table 2 corresponding to the 
one from table 1 used in step 9.3.9. Using this appropriate expression, 
determine Q<INF>std</INF> for the initial flow rate from the sampler 
calibration curve, either graphically or from the transposed regression 
equation:

Q<INF>std</INF> =
1/m ([Appropriate expression from table 2]-b)

Similarly, determine Q<INF>std</INF> from the final flow reading, and 
calculate the average flow Q<INF>std</INF> as one-half the sum of the 
initial and final flow rates.
    10.1.2 For a sampler with a continuous flow recorder, determine the 
average flow rate device reading, I, for the period. Determine the 
appropriate expression from table 2 corresponding to the one from table 
1 used in step 9.3.9. Then using this expression and the average flow 
rate reading, determine Q<INF>std</INF> from the sampler calibration 
curve, either graphically or from the transposed regression equation:

Q<INF>std</INF> =

1/m ([Appropriate expression from table 2]-b)
    If the trace shows substantial flow change during the sampling 
period, greater accuracy may be achieved by dividing the sampling period 
into intervals and calculating an average reading before determining 
Q<INF>std</INF>.
    10.2 Calculate the total air volume sampled as:

V-Q<INF>std</INF>x t

where:

V = total air volume sampled, in standard volume units, std m\3\/;
Q<INF>std</INF> = average standard flow rate, std m\3\/min;
t = sampling time, min.

    10.3 Calculate and report the particulate matter concentration as:
    [GRAPHIC] [TIFF OMITTED] TR31AU93.025
    
where:

TSP = mass concentration of total suspended particulate matter, <greek 
mu<ls-thn-eq>g/std m\3\;
W<INF>i</INF> = initial weight of clean filter, g;
W<INF>f</INF> = final weight of exposed filter, g;
V = air volume sampled, converted to standard conditions, std m\3\,
10\6\ = conversion of g to <greek mu<ls-thn-eq>g.

    10.4 If desired, the actual particulate matter concentration (see 
Section 2.2) can be calculated as follows:

(TSP)<INF>a</INF>=TSP (P<INF>3</INF>/P<INF>std</INF>)(298/T<INF>3</INF>)

where:

(TSP)<INF>a</INF> = actual concentration at field conditions, <greek 
mu<ls-thn-eq>g/m\3\;

[[Page 32]]

TSP = concentration at standard conditions, <greek mu<ls-thn-eq>g/std 
m\3\;
P<INF>3</INF> = average barometric pressure during sampling period, mm 
Hg;
P<INF>std</INF> = 760 mn Hg (or 101 kPa);
T<INF>3</INF> = average ambient temperature during sampling period, K.

    11.0 References.
    1. Quality Assurance Handbook for Air Pollution Measurement Systems, 
Volume I, Principles. EPA-600/9-76-005, U.S. Environmental Protection 
Agency, Research Triangle Park, NC 27711, 1976.
    2. Quality Assurance Handbook for Air Pollution Measurement Systems, 
Volume II, Ambient Air Specific Methods. EPA-600/4-77-027a, U.S. 
Environmental Protection Agency, Research Triangle Park, NC 27711, 1977.
    3. Wedding, J. B., A. R. McFarland, and J. E. Cernak. Large Particle 
Collection Characteristics of Ambient Aerosol Samplers. Environ. Sci. 
Technol. 11:387-390, 1977.
    4. McKee, H. C., et al. Collaborative Testing of Methods to Measure 
Air Pollutants, I. The High-Volume Method for Suspended Particulate 
Matter. J. Air Poll. Cont. Assoc., 22 (342), 1972.
    5. Clement, R. E., and F. W. Karasek. Sample Composition Changes in 
Sampling and Analysis of Organic Compounds in Aerosols. The Intern. J. 
Environ. Anal. Chem., 7:109, 1979.
    6. Lee, R. E., Jr., and J. Wagman. A Sampling Anomaly in the 
Determination of Atmospheric Sulfuric Concentration. Am. Ind. Hygiene 
Assoc. J., 27:266, 1966.
    7. Appel, B. R., et al. Interference Effects in Sampling Particulate 
Nitrate in Ambient Air. Atmospheric Environment, 13:319, 1979.
    8. Tierney, G. P., and W. D. Conner. Hygroscopic Effects on Weight 
Determinations of Particulates Collected on Glass-Fiber Filters. Am. 
Ind. Hygiene Assoc. J., 28:363, 1967.
    9. Chahal, H. S., and D. J. Romano. High-Volume Sampling Effect of 
Windborne Particulate Matter Deposited During Idle Periods. J. Air Poll. 
Cont. Assoc., Vol. 26 (885), 1976.
    10. Patterson, R. K. Aerosol Contamination from High-Volume Sampler 
Exhaust. J. Air Poll. Cont. Assoc., Vol. 30 (169), 1980.
    11. EPA Test Procedures for Determining pH and Integrity of High-
Volume Air Filters. QAD/M-80.01. Available from the Methods 
Standardization Branch, Quality Assurance Division, Environmental 
Monitoring Systems Laboratory (MD-77), U.S. Environmental Protection 
Agency, Research Triangle Park, NC 27711, 1980.
    12. Smith, F., P. S. Wohlschlegel, R. S. C. Rogers, and D. J. 
Mulligan. Investigation of Flow Rate Calibration Procedures Associated 
with the High-Volume Method for Determination of Suspended Particulates. 
EPA-600/4-78-047, U.S. Environmental Protection Agency, Research 
Triangle Park, NC, June 1978.
<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

[[Page 33]]

<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

[[Page 34]]

<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

[[Page 35]]

<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

[[Page 36]]

<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

[47 FR 54912, Dec. 6, 1982; 48 FR 17355, Apr. 22, 1983]

 Appendix C to Part 50--Measurement Principle and Calibration Procedure 
for the Measurement of Carbon Monoxide in the Atmosphere (Non-Dispersive 
                          Infrared Photometry)

                          Measurement Principle

    1. Measurements are based on the absorption of infrared radiation by 
carbon monoxide (CO) in a non-dispersive photometer. Infrared energy 
from a source is passed through a cell containing the gas sample to be 
analyzed, and the quantitative absorption of energy by CO in the sample 
cell is measured by a suitable detector. The photometer is sensitized to 
CO by employing CO gas in either the detector or in a filter cell in the 
optical path, thereby limiting the measured absorption to one or more of 
the characteristic wavelengths at which CO strongly absorbs. Optical 
filters or other means may

[[Page 37]]

also be used to limit sensitivity of the photometer to a narrow band of 
interest. Various schemes may be used to provide a suitable zero 
reference for the photometer. The measured absorption is converted to an 
electrical output signal, which is related to the concentration of CO in 
the measurement cell.
    2. An analyzer based on this principle will be considered a 
reference method only if it has been designated as a reference method in 
accordance with part 53 of this chapter.
    3. Sampling considerations.
    The use of a particle filter on the sample inlet line of an NDIR CO 
analyzer is optional and left to the discretion of the user or the 
manufacturer. Use of filter should depend on the analyzer's 
susceptibility to interference, malfunction, or damage due to particles.

                          Calibration Procedure

    1. Principle. Either of two methods may be used for dynamic 
multipoint calibration of CO analyzers:
    (1) One method uses a single certified standard cylinder of CO, 
diluted as necessary with zero air, to obtain the various calibration 
concentrations needed.
    (2) The other method uses individual certified standard cylinders of 
CO for each concentration needed. Additional information on calibration 
may be found in Section 2.0.9 of Reference 1.
    2. Apparatus. The major components and typical configurations of the 
calibration systems for the two calibration methods are shown in Figures 
1 and 2.
    2.1 Flow controller(s). Device capable of adjusting and regulating 
flow rates. Flow rates for the dilution method (Figure 1) must be 
regulated to +\ 1%.
    2.2 Flow meter(s). Calibrated flow meter capable of measuring and 
monitoring flow rates. Flow rates for the dilution method (Figure 1) 
must be measured with an accuracy of +\ 2% of the measured value.
    2.3 Pressure regulator(s) for standard CO cylinder(s). Regulator 
must have nonreactive diaphragm and internal parts and a suitable 
delivery pressure.
    2.4 Mixing chamber. A chamber designed to provide thorough mixing of 
CO and diluent air for the dilution method.
    2.5 Output manifold. The output manifold should be of sufficient 
diameter to insure an insignificant pressure drop at the analyzer 
connection. The system must have a vent designed to insure atmospheric 
pressure at the manifold and to prevent ambient air from entering the 
manifold.
    3. Reagents.
    3.1 CO concentration standard(s). Cylinder(s) of CO in air 
containing appropriate concentrations(s) of CO suitable for the selected 
operating range of the analyzer under calibration; CO standards for the 
dilution method may be contained in a nitrogen matrix if the zero air 
dilution ratio is not less than 100:1. The assay of the cylinder(s) must 
be traceable either to a National Bureau of Standards (NBS) CO in air 
Standard Reference Material (SRM) or to an NBS/EPA-approved commercially 
available Certified Reference Material (CRM). CRM's are described in 
Reference 2, and a list of CRM sources is available from the address 
shown for Reference 2. A recommended protocol for certifying CO gas 
cylinders against either a CO SRM or a CRM is given in Reference 1. CO 
gas cylinders should be recertified on a regular basis as determined by 
the local quality control program.
    3.2 Dilution gas (zero air). Air, free of contaminants which will 
cause a detectable response on the CO analyzer. The zero air should 
contain <0.1 ppm CO. A procedure for generating zero air is given in 
Reference 1.
    4. Procedure Using Dynamic Dilution Method.
    4.1 Assemble a dynamic calibration system such as the one shown in 
Figure 1. All calibration gases including zero air must be introduced 
into the sample inlet of the analyzer system. For specific operating 
instructions refer to the manufacturer's manual.
    4.2 Insure that all flowmeters are properly calibrated, under the 
conditions of use, if appropriate, against an authoritative standard 
such as a soap-bubble meter or wet-test meter. All volumetric flowrates 
should be corrected to 25  deg.C and 760 mm Hg (101 kPa). A discussion 
on calibration of flowmeters is given in Reference 1.
    4.3 Select the operating range of the CO analyzer to be calibrated.
    4.4 Connect the signal output of the CO analyzer to the input of the 
strip chart recorder or other data collection device. All adjustments to 
the analyzer should be based on the appropriate strip chart or data 
device readings. References to analyzer responses in the procedure given 
below refer to recorder or data device responses.
    4.5 Adjust the calibration system to deliver zero air to the output 
manifold. The total air flow must exceed the total demand of the 
analyzer(s) connected to the output manifold to insure that no ambient 
air is pulled into the manifold vent. Allow the analyzer to sample zero 
air until a stable respose is obtained. After the response has 
stabilized, adjust the analyzer zero control. Offsetting the analyzer 
zero adjustments to +5 percent of scale is recommended to facilitate 
observing negative zero drift. Record the stable zero air response as 
Z<INF>CO</INF>.
    4.6 Adjust the zero air flow and the CO flow from the standard CO 
cylinder to provide a diluted CO concentration of approximately 80 
percent of the upper range limit (URL) of the operating range of the 
analyzer. The total air flow must exceed the total demand of the 
analyzer(s) connected to the output manifold to insure that no ambient 
air is

[[Page 38]]

pulled into the manifold vent. The exact CO concentration is calculated 
from:
[GRAPHIC] [TIFF OMITTED] TR31AU93.026

where:

[CO]<INF>OUT</INF> = diluted CO concentration at the output manifold, 
ppm;
[CO]<INF>STD</INF> = concentration of the undiluted CO standard, ppm;
F<INF>CO</INF> = flow rate of the CO standard corrected to 25  deg.C and 
760 mm Hg, (101 kPa), L/min; and
F<INF>D</INF> = flow rate of the dilution air corrected to 25  deg.C and 
760 mm Hg, (101 kPa), L/min.

    Sample this CO concentration until a stable response is obtained. 
Adjust the analyzer span control to obtain a recorder response as 
indicated below:

Recorder response (percent scale) =

[GRAPHIC] [TIFF OMITTED] TR31AU93.027

where:

URL = nominal upper range limit of the analyzer's operating range, and
Z<INF>CO</INF> = analyzer response to zero air, % scale.

    If substantial adjustment of the analyzer span control is required, 
it may be necessary to recheck the zero and span adjustments by 
repeating Steps 4.5 and 4.6. Record the CO concentration and the 
analyzer's response. 4.7 Generate several additional concentrations (at 
least three evenly spaced points across the remaining scale are 
suggested to verify linearity) by decreasing F<INF>CO</INF> or 
increasing F<INF>D.</INF> Be sure the total flow exceeds the analyzer's 
total flow demand. For each concentration generated, calculate the exact 
CO concentration using Equation (1). Record the concentration and the 
analyzer's response for each concentration. Plot the analyzer responses 
versus the corresponding CO concentrations and draw or calculate the 
calibration curve.
    5. Procedure Using Multiple Cylinder Method. Use the procedure for 
the dynamic dilution method with the following changes:
    5.1 Use a multi-cylinder system such as the typical one shown in 
Figure 2.
    5.2 The flowmeter need not be accurately calibrated, provided the 
flow in the output manifold exceeds the analyzer's flow demand.
    5.3 The various CO calibration concentrations required in Steps 4.6 
and 4.7 are obtained without dilution by selecting the appropriate 
certified standard cylinder.

                               References

    1. Quality Assurance Handbook for Air Pollution Measurement Systems, 
Volume II--Ambient Air Specific Methods, EPA-600/4-77-027a, U.S. 
Environmental Protection Agency, Environmental Monitoring Systems 
Laboratory, Research Triangle Park, NC 27711, 1977.
    2. A procedure for Establishing Traceability of Gas Mixtures to 
Certain National Bureau of Standards Standard Reference Materials. EPA-
600/7-81-010, U.S. Environmental Protection Agency, Environmental 
Monitoring Systems Laboratory (MD-77), Research Triangle Park, NC 27711, 
January 1981.

[[Page 39]]

<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

[[Page 40]]

<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

[47 FR 54922, Dec. 6, 1982; 48 FR 17355, Apr. 22, 1983]

[[Page 41]]

 Appendix D to Part 50--Measurement Principle and Calibration Procedure 
             for the Measurement of Ozone in the Atmosphere

                          measurement principle

    1. Ambient air and ethylene are delivered simultaneously to a mixing 
zone where the ozone in the air reacts with the ethylene to emit light, 
which is detected by a photomultiplier tube. The resulting photocurrent 
is amplified and is either read directly or displayed on a recorder.
    2. An analyzer based on this principle will be considered a 
reference method only if it has been designated as a reference method in 
accordance with part 53 of this chapter and calibrated as follows:

                          calibration procedure

    1. Principle. The calibration procedure is based on the photometric 
assay of ozone (O<INF>3</INF>) concentrations in a dynamic flow system. 
The concentration of O<INF>3</INF> in an absorption cell is determined 
from a measurement of the amount of 254 nm light absorbed by the sample. 
This determination requires knowledge of (1) the absorption coefficient 
(<<SUP>greek</SUP> alphals-thn-eq</SUP>) of O<INF>3</INF> at 254 nm, (2) 
the optical path length (l) through the sample, (3) the transmittance of 
the sample at a wavelength of 254 nm, and (4) the temperature (T) and 
pressure (P) of the sample. The transmittance is defined as the ratio I/
I<INF>0,</INF> where I is the intensity of light which passes through 
the cell and is sensed by the detector when the cell contains an O<INF>3</INF> 
sample, and I<INF>0</INF> is the intensity of light which passes through 
the cell and is sensed by the detector when the cell contains zero air. 
It is assumed that all conditions of the system, except for the contents 
of the absorption cell, are identical during measurement of I and 
I<INF>0.</INF> The quantities defined above are related by the Beer-
Lambert absorption law,
[GRAPHIC] [TIFF OMITTED] TR31AU93.028

where:

<<SUP>greek</SUP> alphals-thn-eq</SUP> = absorption coefficient of 
O<INF>3</INF> at 254 nm=308<SUP>+</SUP>\4 atm<SUP>-1</SUP> cm<SUP>-1</SUP> 
at 0  deg.C and 760 torr. <SUP>(1, 2, 3, 4, 5, 6, 7)</SUP>
c = O<INF>3</INF> concentration in atmospheres
l = optical path length in cm

    In practice, a stable O<INF>3</INF> generator is used to produce 
O<INF>3</INF> concentrations over the required range. Each O<INF>3</INF> 
concentration is determined from the measurement of the transmittance 
(I/I<INF>0</INF>) of the sample at 254 nm with a photometer of path 
length l and calculated from the equation,
[GRAPHIC] [TIFF OMITTED] TR31AU93.029

The calculated O<INF>3</INF> concentrations must be corrected for 
O<INF>3</INF> losses which may occur in the photometer and for the 
temperature and pressure of the sample.
    2. Applicability. This procedure is applicable to the calibration of 
ambient air O<INF>3</INF> analyzers, either directly or by means of a 
transfer standard certified by this procedure. Transfer standards must 
meet the requirements and specifications set forth in Reference 8.
    3. Apparatus. A complete UV calibration system consists of an ozone 
generator, an output port or manifold, a photometer, an appropriate 
source of zero air, and other components as necessary. The configuration 
must provide a stable ozone concentration at the system output and allow 
the photometer to accurately assay the output concentration to the 
precision specified for the photometer (3.1). Figure 1 shows a commonly 
used configuration and serves to illustrate the calibration procedure 
which follows. Other configurations may require appropriate variations 
in the procedural steps. All connections between components in the 
calibration system downstream of the O<INF>3</INF> generator should be 
of glass, Teflon, or other relatively inert materials. Additional 
information regarding the assembly of a UV photometric calibration 
apparatus is given in Reference 9. For certification of transfer 
standards which provide their own source of O<INF>3,</INF> the transfer 
standard may replace the O<INF>3</INF> generator and possibly other 
components shown in Figure 1; see Reference 8 for guidance.
    3.1 UV photometer. The photometer consists of a low-pressure mercury 
discharge lamp, (optional) collimation optics, an absorption cell, a 
detector, and signal-processing electronics, as illustrated in Figure 1. 
It must be capable of measuring the transmittance, I/I<INF>0,</INF> at a 
wavelength of 254 nm with sufficient precision such that the standard 
deviation of the concentration measurements does not exceed the greater 
of 0.005 ppm or 3% of the concentration. Because the low-pressure 
mercury lamp radiates at several wavelengths, the photometer must 
incorporate suitable means to assure that no O<INF>3</INF> is generated 
in the cell by the lamp, and that at least 99.5% of the radiation sensed 
by the detector is 254 nm radiation. (This can be readily achieved by 
prudent selection of optical filter and detector response 
characteristics.) The length of the light path through the absorption 
cell must be known with an accuracy of at least 99.5%. In addition, the 
cell and associated plumbing must be designed to

[[Page 42]]

minimize loss of O<INF>3</INF> from contact with cell walls and gas 
handling components. See Reference 9 for additional information.
    3.2 Air flow controllers. Devices capable of regulating air flows as 
necessary to meet the output stability and photometer precision 
requirements.
    3.3 Ozone generator. Device capable of generating stable levels of 
O<INF>3</INF> over the required concentration range.
    3.4 Output manifold. The output manifold should be constructed of 
glass, Teflon, or other relatively inert material, and should be of 
sufficient diameter to insure a negligible pressure drop at the 
photometer connection and other output ports. The system must have a 
vent designed to insure atmospheric pressure in the manifold and to 
prevent ambient air from entering the manifold.
    3.5 Two-way valve. Manual or automatic valve, or other means to 
switch the photometer flow between zero air and the O<INF>3</INF> 
concentration.
    3.6 Temperature indicator. Accurate to <SUP>+</SUP>\1  deg.C.
    3.7 Barometer or pressure indicator. Accurate to <SUP>+</SUP>\2 
torr.
    4. Reagents.
    4.1 Zero air. The zero air must be free of contaminants which would 
cause a detectable response from the O<INF>3</INF> analyzer, and it 
should be free of NO, C<INF>2</INF> H<INF>4,</INF> and other species 
which react with O<INF>3.</INF> A procedure for generating suitable zero 
air is given in Reference 9. As shown in Figure 1, the zero air supplied 
to the photometer cell for the I<INF>0</INF> reference measurement must 
be derived from the same source as the zero air used for generation of 
the ozone concentration to be assayed (I measurement). When using the 
photometer to certify a transfer standard having its own source of 
ozone, see Reference 8 for guidance on meeting this requirement.
    5. Procedure.
    5.1 General operation. The calibration photometer must be dedicated 
exclusively to use as a calibration standard. It should always be used 
with clean, filtered calibration gases, and never used for ambient air 
sampling. Consideration should be given to locating the calibration 
photometer in a clean laboratory where it can be stationary, protected 
from physical shock, operated by a responsible analyst, and used as a 
common standard for all field calibrations via transfer standards.
    5.2 Preparation. Proper operation of the photometer is of critical 
importance to the accuracy of this procedure. The following steps will 
help to verify proper operation. The steps are not necessarily required 
prior to each use of the photometer. Upon initial operation of the 
photometer, these steps should be carried out frequently, with all 
quantitative results or indications recorded in a chronological record 
either in tabular form or plotted on a graphical chart. As the 
performance and stability record of the photometer is established, the 
frequency of these steps may be reduced consistent with the documented 
stability of the photometer.
    5.2.1 Instruction manual: Carry out all set up and adjustment 
procedures or checks as described in the operation or instruction manual 
associated with the photometer.
    5.2.2 System check: Check the photometer system for integrity, 
leaks, cleanliness, proper flowrates, etc. Service or replace filters 
and zero air scrubbers or other consumable materials, as necessary.
    5.2.3 Linearity: Verify that the photometer manufacturer has 
adequately established that the linearity error of the photometer is 
less than 3%, or test the linearity by dilution as follows: Generate and 
assay an O<INF>3</INF> concentration near the upper range limit of the 
system (0.5 or 1.0 ppm), then accurately dilute that concentration with 
zero air and reassay it. Repeat at several different dilution ratios. 
Compare the assay of the original concentration with the assay of the 
diluted concentration divided by the dilution ratio, as follows
[GRAPHIC] [TIFF OMITTED] TR31AU93.030

where:

E = linearity error, percent
A<INF>1</INF> = assay of the original concentration
A<INF>2</INF> = assay of the diluted concentration
R = dilution ratio = flow of original concentration divided by the total 
flow

    The linearity error must be less than 5%. Since the accuracy of the 
measured flow-rates will affect the linearity error as measured this 
way, the test is not necessarily conclusive. Additional information on 
verifying linearity is contained in Reference 9.
    5.2.4 Intercomparison: When possible, the photometer should be 
occasionally intercompared, either directly or via transfer standards, 
with calibration photometers used by other agencies or laboratories.
    5.2.5 Ozone losses: Some portion of the O<INF>3</INF> may be lost 
upon contact with the photometer cell walls and gas handling components. 
The magnitude of this loss must be determined and used to correct the 
calculated O<INF>3</INF> concentration. This loss must not exceed 5%. 
Some guidelines for quantitatively determining this loss are discussed 
in Reference 9.
    5.3 Assay of O<INF>3</INF> concentrations.
    5.3.1 Allow the photometer system to warm up and stabilizer.
    5.3.2 Verify that the flowrate through the photometer absorption 
cell, F allows the cell to be flushed in a reasonably short period of 
time (2 liter/min is a typical flow). The precision of the measurements 
is inversely related to the time required for flushing, since the 
photometer drift error increases with time.

[[Page 43]]

    5.3.3 Insure that the flowrate into the output manifold is at least 
1 liter/min greater than the total flowrate required by the photometer 
and any other flow demand connected to the manifold.
    5.3.4 Insure that the flowrate of zero air, F<INF>z,</INF> is at 
least 1 liter/min greater than the flowrate required by the photometer.
    5.3.5 With zero air flowing in the output manifold, actuate the two-
way valve to allow the photometer to sample first the manifold zero air, 
then F<INF>z.</INF> The two photometer readings must be equal 
(I=I<INF>o</INF>).
    Note: In some commercially available photometers, the operation of 
the two-way valve and various other operations in section 5.3 may be 
carried out automatically by the photometer.
    5.3.6 Adjust the O<INF>3</INF> generator to produce an O<INF>3</INF> 
concentration as needed.
    5.3.7 Actuate the two-way valve to allow the photometer to sample 
zero air until the absorption cell is thoroughly flushed and record the 
stable measured value of I<INF>o</INF>.
    5.3.8 Actuate the two-way valve to allow the photometer to sample 
the ozone concentration until the absorption cell is thoroughly flushed 
and record the stable measured value of I.
    5.3.9 Record the temperature and pressure of the sample in the 
photometer absorption cell. (See Reference 9 for guidance.)
    5.3.10 Calculate the O<INF>3</INF> concentration from equation 4. An 
average of several determinations will provide better precision.
[GRAPHIC] [TIFF OMITTED] TR31AU93.032

where:

[O<INF>3</INF>]<INF>OUT</INF> = O<INF>3</INF> concentration, ppm
<<SUP>greek</SUP> alphals-thn-eq</SUP> = absorption coefficient of 
O<INF>3</INF> at 254 nm=308 atm<SUP>-1</SUP> cm<SUP>-1</SUP> at 0  deg.C 
and 760 torr
l = optical path length, cm
T = sample temperature, K
P = sample pressure, torr
L = correction factor for O<INF>3</INF> losses from 5.2.5=(1-fraction 
O<INF>3</INF> lost).

    Note: Some commercial photometers may automatically evaluate all or 
part of equation 4. It is the operator's responsibility to verify that 
all of the information required for equation 4 is obtained, either 
automatically by the photometer or manually. For ``automatic'' 
photometers which evaluate the first term of equation 4 based on a 
linear approximation, a manual correction may be required, particularly 
at higher O<INF>3</INF> levels. See the photometer instruction manual 
and Reference 9 for guidance.
    5.3.11 Obtain additional O<INF>3</INF> concentration standards as 
necessary by repeating steps 5.3.6 to 5.3.10 or by Option 1.
    5.4 Certification of transfer standards. A transfer standard is 
certified by relating the output of the transfer standard to one or more 
ozone standards as determined according to section 5.3. The exact 
procedure varies depending on the nature and design of the transfer 
standard. Consult Reference 8 for guidance.
    5.5 Calibration of ozone analyzers. Ozone analyzers are calibrated 
as follows, using ozone standards obtained directly according to section 
5.3 or by means of a certified transfer standard.
    5.5.1 Allow sufficient time for the O<INF>3</INF> analyzer and the 
photometer or transfer standard to warmup and stabilize.
    5.5.2 Allow the O<INF>3</INF> analyzer to sample zero air until a 
stable response is obtained and adjust the O<INF>3</INF> analyzer's zero 
control. Offsetting the analyzer's zero adjustment to +5% of scale is 
recommended to facilitate observing negative zero drift. Record the 
stable zero air response as ``Z''.
    5.5.3 Generate an O<INF>3</INF> concentration standard of 
approximately 80% of the desired upper range limit (URL) of the O<INF>3</INF> 
analyzer. Allow the O<INF>3</INF> analyzer to sample this O<INF>3</INF> 
concentration standard until a stable response is obtained.
    5.5.4 Adjust the O<INF>3</INF> analyzer's span control to obtain a 
convenient recorder response as indicated below:
    recorder response (%scale) =
    [GRAPHIC] [TIFF OMITTED] TR31AU93.033
    
where:

URL = upper range limit of the O<INF>3</INF> analyzer, ppm
Z = recorder response with zero air, % scale

    Record the O<INF>3</INF> concentration and the corresponding 
analyzer response. If substantial adjustment of the span control is 
necessary, recheck the zero and span adjustments by repeating steps 
5.5.2 to 5.5.4.
    5.5.5 Generate several other O<INF>3</INF> concentration standards 
(at least 5 others are recommended) over the scale range of the O<INF>3</INF> 
analyzer by adjusting the O<INF>3</INF> source or by Option 1. For each 
O<INF>3</INF> concentration standard, record the O<INF>3</INF> and the 
corresponding analyzer response.
    5.5.6 Plot the O<INF>3</INF> analyzer responses versus the 
corresponding O<INF>3</INF> concentrations and draw the O<INF>3</INF> 
analyzer's calibration curve or calculate the appropriate response 
factor.
    5.5.7 Option 1: The various O<INF>3</INF> concentrations required in 
steps 5.3.11 and 5.5.5 may be obtained by dilution of the O<INF>3</INF> 
concentration generated in steps 5.3.6 and 5.5.3. With this option, 
accurate flow measurements are required. The dynamic calibration system 
may be modified as shown in Figure 2 to allow for dilution air to be 
metered in downstream of the O<INF>3</INF> generator. A mixing chamber 
between the O<INF>3</INF> generator and the output manifold is also 
required. The flowrate through the O<INF>3</INF> generator 
(F<INF>o</INF>) and the dilution air flowrate

[[Page 44]]

(F<INF>D</INF>) are measured with a reliable flow or volume standard 
traceable to NBS. Each O<INF>3</INF> concentration generated by dilution 
is calculated from:
[GRAPHIC] [TIFF OMITTED] TR31AU93.031

where:

[O<INF>3</INF>]`<INF>OUT</INF> = diluted O<INF>3</INF> concentration, 
ppm
F<INF>0</INF> = flowrate through the O<INF>3</INF> generator, liter/min
F<INF>D</INF> = diluent air flowrate, liter/min

                               References

    1. E.C.Y. Inn and Y. Tanaka, ``Absorption coefficient of Ozone in 
the Ultraviolet and Visible Regions'', J. Opt. Soc. Am., 43, 870 (1953).
    2. A. G. Hearn, ``Absorption of Ozone in the Ultraviolet and Visible 
Regions of the Spectrum'', Proc. Phys. Soc. (London), 78, 932 (1961).
    3. W. B. DeMore and O. Raper, ``Hartley Band Extinction Coefficients 
of Ozone in the Gas Phase and in Liquid Nitrogen, Carbon Monoxide, and 
Argon'', J. Phys. Chem., 68, 412 (1964).
    4. M. Griggs, ``Absorption Coefficients of Ozone in the Ultraviolet 
and Visible Regions'', J. Chem. Phys., 49, 857 (1968).
    5. K. H. Becker, U. Schurath, and H. Seitz, ``Ozone Olefin Reactions 
in the Gas Phase. 1. Rate Constants and Activation Energies'', Int'l 
Jour. of Chem. Kinetics, VI, 725 (1974).
    6. M. A. A. Clyne and J. A. Coxom, ``Kinetic Studies of Oxy-halogen 
Radical Systems'', Proc. Roy. Soc., A303, 207 (1968).
    7. J. W. Simons, R. J. Paur, H. A. Webster, and E. J. Bair, ``Ozone 
Ultraviolet Photolysis. VI. The Ultraviolet Spectrum'', J. Chem. Phys., 
59, 1203 (1973).
    8. Transfer Standards for Calibration of Ambient Air Monitoring 
Analyzers for Ozone, EPA publication number EPA-600/4-79-056, EPA, 
National Exposure Research Laboratory, Department E, (MD-77B), Research 
Triangle Park, NC 27711.
    9. Technical Assistance Document for the Calibration of Ambient 
Ozone Monitors, EPA publication number EPA-600/4-79-057, EPA, National 
Exposure Research Laboratory, Department E, (MD-77B), Research Triangle 
Park, NC 27711.

[[Page 45]]

<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

[[Page 46]]

[44 FR 8224, Feb. 8, 1979, as amended at 62 FR 38895, July 18, 1997]

                    Appendix E to Part 50 [Reserved]

 Appendix F to Part 50--Measurement Principle and Calibration Procedure 
  for the Measurement of Nitrogen Dioxide in the Atmosphere (Gas Phase 
                           Chemiluminescence)

                       Principle and Applicability

    1. Atmospheric concentrations of nitrogen dioxide (NO<INF>2</INF>) 
are measured indirectly by photometrically measuring the light 
intensity, at wavelengths greater than 600 nanometers, resulting from 
the chemiluminescent reaction of nitric oxide (NO) with ozone 
(O<INF>3</INF>). (1,2,3) NO<INF>2</INF> is first quantitatively reduced 
to NO(4,5,6) by means of a converter. NO, which commonly exists in 
ambient air together with NO<INF>2,</INF> passes through the converter 
unchanged causing a resultant total NO<INF>X</INF> concentration equal 
to NO+NO<INF>2.</INF> A sample of the input air is also measured without 
having passed through the converted. This latter NO measurement is 
subtracted from the former measurement (NO+NO<INF>2</INF>) to yield the 
final NO<INF>2</INF> measurement. The NO and NO+NO<INF>2</INF> 
measurements may be made concurrently with dual systems, or cyclically 
with the same system provided the cycle time does not exceed 1 minute.
    2. Sampling considerations.
    2.1 Chemiluminescence NO/NO<INF>X</INF>/NO<INF>2</INF> analyzers 
will respond to other nitrogen containing compounds, such as 
peroxyacetyl nitrate (PAN), which might be reduced to NO in the thermal 
converter. (7) Atmospheric concentrations of these potential 
interferences are generally low relative to NO<INF>2</INF> and valid 
NO<INF>2</INF> measurements may be obtained. In certain geographical 
areas, where the concentration of these potential interferences is known 
or suspected to be high relative to NO<INF>2,</INF> the use of an 
equivalent method for the measurement of NO<INF>2</INF> is recommended.
    2.2 The use of integrating flasks on the sample inlet line of 
chemiluminescence NO/NO<INF>X</INF>/NO<INF>2</INF> analyzers is optional 
and left to couraged. The sample residence time between the sampling 
point and the analyzer should be kept to a minimum to avoid erroneous 
NO<INF>2</INF> measurements resulting from the reaction of ambient 
levels of NO and O<INF>3</INF> in the sampling system.
    2.3 The use of particulate filters on the sample inlet line of 
chemiluminescence NO/NO<INF>X</INF>/NO<INF>2</INF> analyzers is optional 
and left to the discretion of the user or the manufacturer.
Use of the filter should depend on the analyzer's susceptibility to 
interference, malfunction, or damage due to particulates. Users are 
cautioned that particulate matter concentrated on a filter may cause 
erroneous NO<INF>2</INF> measurements and therefore filters should be 
changed frequently.
    3. An analyzer based on this principle will be considered a 
reference method only if it has been designated as a reference method in 
accordance with part 53 of this chapter.

                               Calibration

    1. Alternative A--Gas phase titration (GPT) of an NO standard with 
O<INF>3</INF>.
    Major equipment required: Stable O<INF>3</INF> generator. 
Chemiluminescence NO/NO<INF>X</INF>/NO<INF>2</INF> analyzer with strip 
chart recorder(s). NO concentration standard.
    1.1 Principle. This calibration technique is based upon the rapid 
gas phase reaction between NO and O<INF>3</INF> to produce 
stoichiometric quantities of NO<INF>2</INF> in accordance with the 
following equation: (8)
[GRAPHIC] [TIFF OMITTED] TC08NO91.075

The quantitative nature of this reaction is such that when the NO 
concentration is known, the concentration of NO<INF>2</INF> can be 
determined. Ozone is added to excess NO in a dynamic calibration system, 
and the NO channel of the chemiluminescence NO/NO<INF>X</INF>/NO<INF>2</INF> 
analyzer is used as an indicator of changes in NO concentration. Upon 
the addition of O<INF>3,</INF> the decrease in NO concentration observed 
on the calibrated NO channel is equivalent to the concentration of 
NO<INF>2</INF> produced. The amount of NO<INF>2</INF> generated may be 
varied by adding variable amounts of O<INF>3</INF> from a stable 
uncalibrated O<INF>3</INF> generator. (9)
    1.2 Apparatus. Figure 1, a schematic of a typical GPT apparatus, 
shows the suggested configuration of the components listed below. All 
connections between components in the calibration system downstream from 
the O<INF>3</INF> generator should be of glass, 
Teflon<SUP><register mark<ls-thn-eq>,</SUP> or other non-reactive 
material.
    1.2.1 Air flow controllers. Devices capable of maintaining constant 
air flows within <SUP>+</SUP>\2% of the required flowrate.
    1.2.2 NO flow controller. A device capable of maintaining constant 
NO flows within <SUP>+</SUP>\2% of the required flowrate. Component 
parts in contact with the NO should be of a non-reactive material.
    1.2.3 Air flowmeters. Calibrated flowmeters capable of measuring and 
monitoring air flowrates with an accuracy of <SUP>+</SUP>\2% of the 
measured flowrate.
    1.2.4 NO flowmeter. A calibrated flowmeter capable of measuring and 
monitoring NO flowrates with an accuracy of <SUP>+</SUP>\2% of the 
measured flowrate. (Rotameters have been reported to operate unreliably 
when measuring low NO flows and are not recommended.)
    1.2.5 Pressure regulator for standard NO cylinder. This regulator 
must have a nonreactive diaphragm and internal parts and a suitable 
delivery pressure.

[[Page 47]]

    1.2.6 Ozone generator. The generator must be capable of generating 
sufficient and stable levels of O<INF>3</INF> for reaction with NO to 
generate NO<INF>2</INF> concentrations in the range required. Ozone 
generators of the electric discharge type may produce NO and NO<INF>2</INF> 
and are not recommended.
    1.2.7 Valve. A valve may be used as shown in Figure 1 to divert the 
NO flow when zero air is required at the manifold. The valve should be 
constructed of glass, Teflon<SUP><register mark<ls-thn-eq>,</SUP> or 
other nonreactive material.
    1.2.8 Reaction chamber. A chamber, constructed of glass, 
Teflon<SUP><register mark<ls-thn-eq>,</SUP> or other nonreactive 
material, for the quantitative reaction of O<INF>3</INF> with excess NO. 
The chamber should be of sufficient volume (V<INF>RC</INF>) such that 
the residence time (t<INF>R</INF>) meets the requirements specified in 
1.4. For practical reasons, t<INF>R</INF> should be less than 2 minutes.
    1.2.9 Mixing chamber. A chamber constructed of glass, 
Teflon<SUP><register mark<ls-thn-eq>,</SUP> or other nonreactive 
material and designed to provide thorough mixing of reaction products 
and diluent air. The residence time is not critical when the dynamic 
parameter specification given in 1.4 is met.
    1.2.10 Output manifold. The output manifold should be constructed of 
glass, Teflon<SUP><register mark<ls-thn-eq>,</SUP> or other non-reactive 
material and should be of sufficient diameter to insure an insignificant 
pressure drop at the analyzer connection. The system must have a vent 
designed to insure atmospheric pressure at the manifold and to prevent 
ambient air from entering the manifold.
    1.3 Reagents.
    1.3.1 NO concentration standard. Gas cylinder standard containing 50 
to 100 ppm NO in N<INF>2</INF> with less than 1 ppm NO<INF>2.</INF> This 
standard must be traceable to a National Bureau of Standards (NBS) NO in 
N<INF>2</INF> Standard Reference Material (SRM 1683 or SRM 1684), an NBS 
NO<INF>2</INF> Standard Reference Material (SRM 1629), or an NBS/EPA-
approved commercially available Certified Reference Material (CRM). 
CRM's are described in Reference 14, and a list of CRM sources is 
available from the address shown for Reference 14. A recommended 
protocol for certifying NO gas cylinders against either an NO SRM or CRM 
is given in section 2.0.7 of Reference 15. Reference 13 gives procedures 
for certifying an NO gas cylinder against an NBS NO<INF>2</INF> SRM and 
for determining the amount of NO<INF>2</INF> impurity in an NO cylinder.
    1.3.2 Zero air. Air, free of contaminants which will cause a 
detectable response on the NO/NO<INF>X</INF>/NO<INF>2</INF> analyzer or 
which might react with either NO, O<INF>3,</INF> or NO<INF>2</INF> in 
the gas phase titration. A procedure for generating zero air is given in 
reference 13.
    1.4 Dynamic parameter specification.
    1.4.1 The O<INF>3</INF> generator air flowrate (F<INF>0</INF>) and 
NO flowrate (F<INF>NO</INF>) (see Figure 1) must be adjusted such that 
the following relationship holds:
[GRAPHIC] [TIFF OMITTED] TC08NO91.076

[GRAPHIC] [TIFF OMITTED] TC08NO91.077

[GRAPHIC] [TIFF OMITTED] TC08NO91.078

where:

P<INF>R</INF> = dynamic parameter specification, determined empirically, 
to insure complete reaction of the available O<INF>3,</INF> ppm-minute
[NO]<INF>RC</INF> = NO concentration in the reaction chamber, ppm
<INF>R</INF> = residence time of the reactant gases in the reaction 
chamber, minute
[NO]<INF>STD</INF> = concentration of the undiluted NO standard, ppm
F<INF>NO</INF> = NO flowrate, scm<SUP> 3</SUP>/min
F<INF>O</INF> = O<INF>3</INF> generator air flowrate, scm<SUP> 3</SUP>/
min
V<INF>RC</INF> = volume of the reaction chamber, scm<SUP> 3</SUP>

    1.4.2 The flow conditions to be used in the GPT system are 
determined by the following procedure:
    (a) Determine F<INF>T,</INF> the total flow required at the output 
manifold (F<INF>T</INF>=analyzer demand plus 10 to 50% excess).
    (b) Establish [NO]<INF>OUT</INF> as the highest NO concentration 
(ppm) which will be required at the output manifold. [NO]<INF>OUT</INF> 
should be approximately equivalent to 90% of the upper range limit (URL) 
of the NO<INF>2</INF> concentration range to be covered.
    (c) Determine F<INF>NO</INF> as
    [GRAPHIC] [TIFF OMITTED] TC08NO91.079
    
    (d) Select a convenient or available reaction chamber volume. 
Initially, a trial V<INF>RC</INF> may be selected to be in the range of 
approximately 200 to 500 scm\3\.
    (e) Compute FO as
    <GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>
    
    (f) Compute t<INF>R</INF> as
    [GRAPHIC] [TIFF OMITTED] TC08NO91.080
    
Verify that t<INF>R</INF> < 2 minutes. If not, select a reaction chamber 
with a smaller V<INF>RC</INF>.
    (g) Compute the diluent air flowrate as
    [GRAPHIC] [TIFF OMITTED] TC08NO91.081
    
where:

F<INF>D</INF> = diluent air flowrate, scm<SUP> 3</SUP>/min

[[Page 48]]

    (h) If F<INF>O</INF> turns out to be impractical for the desired 
system, select a reaction chamber having a different V<INF>RC</INF> and 
recompute F<INF>O</INF> and F<INF>D</INF>.
    Note: A dynamic parameter lower than 2.75 ppm-minutes may be used if 
it can be determined empirically that quantitative reaction of O<INF>3</INF> 
with NO occurs. A procedure for making this determination as well as a 
more detailed discussion of the above requirements and other related 
considerations is given in reference 13.
    1.5 Procedure.
    1.5.1 Assemble a dynamic calibration system such as the one shown in 
Figure 1.
    1.5.2 Insure that all flowmeters are calibrated under the conditions 
of use against a reliable standard such as a soap-bubble meter or wet-
test meter. All volumetric flowrates should be corrected to 25  deg.C 
and 760 mm Hg. A discussion on the calibration of flowmeters is given in 
reference 13.
    1.5.3 Precautions must be taken to remove O<INF>2</INF> and other 
contaminants from the NO pressure regulator and delivery system prior to 
the start of calibration to avoid any conversion of the standard NO to 
NO<INF>2.</INF> Failure to do so can cause significant errors in 
calibration. This problem may be minimized by (1) carefully evacuating 
the regulator, when possible, after the regulator has been connected to 
the cylinder and before opening the cylinder valve; (2) thoroughly 
flushing the regulator and delivery system with NO after opening the 
cylinder valve; (3) not removing the regulator from the cylinder between 
calibrations unless absolutely necessary. Further discussion of these 
procedures is given in reference 13.
    1.5.4 Select the operating range of the NO/NO<INF>X</INF>/NO<INF>2</INF> 
analyzer to be calibrated. In order to obtain maximum precision and 
accuracy for NO<INF>2</INF> calibration, all three channels of the 
analyzer should be set to the same range. If operation of the NO and 
NO<INF>X</INF> channels on higher ranges is desired, subsequent 
recalibration of the NO and NO<INF>X</INF> channels on the higher ranges 
is recommended.
    Note: Some analyzer designs may require identical ranges for NO, 
NO<INF>X,</INF> and NO<INF>2</INF> during operation of the analyzer.
    1.5.5 Connect the recorder output cable(s) of the NO/NO<INF>X</INF>/
NO<INF>2</INF> analyzer to the input terminals of the strip chart 
recorder(s). All adjustments to the analyzer should be performed based 
on the appropriate strip chart readings. References to analyzer 
responses in the procedures given below refer to recorder responses.
    1.5.6 Determine the GPT flow conditions required to meet the dynamic 
parameter specification as indicated in 1.4.
    1.5.7 Adjust the diluent air and O<INF>3</INF> generator air flows 
to obtain the flows determined in section 1.4.2. The total air flow must 
exceed the total demand of the analyzer(s) connected to the output 
manifold to insure that no ambient air is pulled into the manifold vent. 
Allow the analyzer to sample zero air until stable NO, NO<INF>X,</INF> 
and NO<INF>2</INF> responses are obtained. After the responses have 
stabilized, adjust the analyzer zero control(s).
    Note: Some analyzers may have separate zero controls for NO, 
NO<INF>X,</INF> and NO<INF>2.</INF> Other analyzers may have separate 
zero controls only for NO and NO<INF>X,</INF> while still others may 
have only one zero control common to all three channels.
    Offsetting the analyzer zero adjustments to +5 percent of scale is 
recommended to facilitate observing negative zero drift. Record the 
stable zero air responses as Z<INF>NO,</INF> Znox, and Zno2.
    1.5.8 Preparation of NO and NO<INF>X</INF> calibration curves.
    1.5.8.1 Adjustment of NO span control. Adjust the NO flow from the 
standard NO cylinder to generate an NO concentration of approximately 80 
percent of the upper range limit (URL) of the NO range. This exact NO 
concentration is calculated from:
[GRAPHIC] [TIFF OMITTED] TR31AU93.044

where:

[NO]<INF>OUT</INF> = diluted NO concentration at the output manifold, 
ppm

Sample this NO concentration until the NO and NO<INF>X</INF> responses 
have stabilized. Adjust the NO span control to obtain a recorder 
response as indicated below:

recorder response (percent scale) =
[GRAPHIC] [TIFF OMITTED] TR31AU93.045

where:

URL = nominal upper range limit of the NO channel, ppm
    Note: Some analyzers may have separate span controls for NO, 
NO<INF>X,</INF> and NO<INF>2.</INF> Other analyzers may have separate 
span controls only for NO and NO<INF>X,</INF> while still others may 
have only one span control common to all three channels. When only one 
span control is available, the span adjustment is made on the NO channel 
of the analyzer.
If substantial adjustment of the NO span control is necessary, it may be 
necessary to recheck the zero and span adjustments by repeating steps 
1.5.7 and 1.5.8.1. Record the NO concentration and the analyzer's NO 
response.
    1.5.8.2 Adjustment of NO<INF>X</INF> span control. When adjusting 
the analyzer's NO<INF>X</INF> span control, the presence of any NO<INF>2</INF> 
impurity in the standard NO cylinder must be taken into account. 
Procedures for determining the amount of NO<INF>2</INF> impurity in the 
standard NO

[[Page 49]]

cylinder are given in reference 13. The exact NO<INF>X</INF> 
concentration is calculated from:
[GRAPHIC] [TIFF OMITTED] TR31AU93.046

where:

[NO<INF>X</INF>]<INF>OUT</INF> = diluted NO<INF>X</INF> concentration at 
the output manifold, ppm
[NO<INF>2</INF>]<INF>IMP</INF> = concentration of NO<INF>2</INF> 
impurity in the standard NO cylinder, ppm

Adjust the NO<INF>X</INF> span control to obtain a recorder response as 
indicated below:

recorder response (% scale) =
[GRAPHIC] [TIFF OMITTED] TR31AU93.047

    Note: If the analyzer has only one span control, the span adjustment 
is made on the NO channel and no further adjustment is made here for 
NO<INF>x.
</INF>If substantial adjustment of the NO<INF>X</INF> span control is 
necessary, it may be necessary to recheck the zero and span adjustments 
by repeating steps 1.5.7 and 1.5.8.2. Record the NO<INF>X</INF> 
concentration and the analyzer's NO<INF>X</INF> response.
    1.5.8.3 Generate several additional concentrations (at least five 
evenly spaced points across the remaining scale are suggested to verify 
linearity) by decreasing F<INF>NO</INF> or increasing F<INF>D.</INF> For 
each concentration generated, calculate the exact NO and NO<INF>X</INF> 
concentrations using equations (9) and (11) respectively. Record the 
analyzer's NO and NO<INF>X</INF> responses for each concentration. Plot 
the analyzer responses versus the respective calculated NO and NO<INF>X</INF> 
concentrations and draw or calculate the NO and NO<INF>X</INF> 
calibration curves. For subsequent calibrations where linearity can be 
assumed, these curves may be checked with a two-point calibration 
consisting of a zero air point and NO and NO<INF>X</INF> concentrations 
of approximately 80% of the URL.
    1.5.9 Preparation of NO<INF>2</INF> calibration curve.
    1.5.9.1 Assuming the NO<INF>2</INF> zero has been properly adjusted 
while sampling zero air in step 1.5.7, adjust F<INF>O</INF> and F<INF>D</INF> 
as determined in section 1.4.2. Adjust F<INF>NO</INF> to generate an NO 
concentration near 90% of the URL of the NO range. Sample this NO 
concentration until the NO and NO<INF>X</INF> responses have stabilized. 
Using the NO calibration curve obtained in section 1.5.8, measure and 
record the NO concentration as [NO]<INF>orig.</INF> Using the NO<INF>X</INF> 
calibration curve obtained in section 1.5.8, measure and record the 
NO<INF>X</INF> concentration as [NO<INF>X</INF>]<INF>orig</INF>.
    1.5.9.2 Adjust the O<INF>3</INF> generator to generate sufficient 
O<INF>3</INF> to produce a decrease in the NO concentration equivalent 
to approximately 80% of the URL of the NO<INF>2</INF> range. The 
decrease must not exceed 90% of the NO concentration determined in step 
1.5.9.1. After the analyzer responses have stabilized, record the 
resultant NO and NO<INF>X</INF> concentrations as [NO]<INF>rem</INF> and 
[NO<INF>X</INF>]<INF>rem</INF>.
    1.5.9.3 Calculate the resulting NO<INF>2</INF> concentration from:
    [GRAPHIC] [TIFF OMITTED] TC08NO91.082
    
where:

[NO<INF>2</INF>]<INF>OUT</INF> = diluted NO<INF>2</INF> concentration at 
the output manifold, ppm
[NO]<INF>orig</INF> = original NO concentration, prior to addition of 
O<INF>3,</INF> ppm
[NO]<INF>rem</INF> = NO concentration remaining after addition of 
O<INF>3,</INF> ppm

Adjust the NO<INF>2</INF> span control to obtain a recorder response as 
indicated below:

recorder response (% scale) =
[GRAPHIC] [TIFF OMITTED] TR31AU93.048

    Note: If the analyzer has only one or two span controls, the span 
adjustments are made on the NO channel or NO and NO<INF>X</INF> channels 
and no further adjustment is made here for NO<INF>2</INF>.
If substantial adjustment of the NO<INF>2</INF> span control is 
necessary, it may be necessary to recheck the zero and span adjustments 
by repeating steps 1.5.7 and 1.5.9.3. Record the NO<INF>2</INF> 
concentration and the corresponding analyzer NO<INF>2</INF> and NO<INF>X</INF> 
responses.
    1.5.9.4 Maintaining the same F<INF>NO,</INF> F<INF>O,</INF> and 
F<INF>D</INF> as in section 1.5.9.1, adjust the ozone generator to 
obtain several other concentrations of NO<INF>2</INF> over the NO<INF>2</INF> 
range (at least five evenly spaced points across the remaining scale are 
suggested). Calculate each NO<INF>2</INF> concentration using equation 
(13) and record the corresponding analyzer NO<INF>2</INF> and NO<INF>X</INF> 
responses. Plot the analyzer's NO<INF>2</INF> responses versus the 
corresponding calculated NO<INF>2</INF> concentrations and draw or 
calculate the NO<INF>2</INF> calibration curve.
    1.5.10 Determination of converter efficiency.

[[Page 50]]

    1.5.10.1 For each NO<INF>2</INF> concentration generated during the 
preparation of the NO<INF>2</INF> calibration curve (see section 1.5.9) 
calculate the concentration of NO<INF>2</INF> converted from:
[GRAPHIC] [TIFF OMITTED] TC08NO91.083

where:

[NO<INF>2</INF>]<INF>CONV</INF> = concentration of NO<INF>2</INF> 
converted, ppm
[NO<INF>X</INF>]<INF>orig</INF> = original NO<INF>X</INF> concentration 
prior to addition of O<INF>3,</INF> ppm
[NO<INF>X</INF>]<INF>rem</INF> = NO<INF>X</INF> concentration remaining 
after addition of O<INF>3,</INF> ppm

    Note: Supplemental information on calibration and other procedures 
in this method are given in reference 13.
Plot [NO<INF>2</INF>]<INF>CONV</INF> (y-axis) versus 
[NO<INF>2</INF>]<INF>OUT</INF> (x-axis) and draw or calculate the 
converter efficiency curve. The slope of the curve times 100 is the 
average converter efficiency, E<INF>C.</INF> The average converter 
efficiency must be greater than 96%; if it is less than 96%, replace or 
service the converter.
    2. Alternative B--NO<INF>2</INF> permeation device.
    Major equipment required:
    Stable O<INF>3</INF> generator.
    Chemiluminescence NO/NO<INF>X</INF>/NO<INF>2</INF> analyzer with 
strip chart recorder(s).
    NO concentration standard.
    NO<INF>2</INF> concentration standard.
    2.1 Principle. Atmospheres containing accurately known 
concentrations of nitrogen dioxide are generated by means of a 
permeation device. (10) The permeation device emits NO<INF>2</INF> at a 
known constant rate provided the temperature of the device is held 
constant (<SUP>+</SUP>\0.1  deg.C) and the device has been accurately 
calibrated at the temperature of use. The NO<INF>2</INF> emitted from 
the device is diluted with zero air to produce NO<INF>2</INF> 
concentrations suitable for calibration of the NO<INF>2</INF> channel of 
the NO/NO<INF>X</INF>/NO<INF>2</INF> analyzer. An NO concentration 
standard is used for calibration of the NO and NO<INF>X</INF> channels 
of the analyzer.
    2.2 Apparatus. A typical system suitable for generating the required 
NO and NO<INF>2</INF> concentrations is shown in Figure 2. All 
connections between components downstream from the permeation device 
should be of glass, Teflon<SUP><register mark<ls-thn-eq>,</SUP> or other 
non-reactive material.
    2.2.1 Air flow controllers. Devices capable of maintaining constant 
air flows within <SUP>+</SUP>\2% of the required flowrate.
    2.2.2 NO flow controller. A device capable of maintaining constant 
NO flows within <SUP>+</SUP>\2% of the required flowrate. Component 
parts in contact with the NO must be of a non-reactive material.
    2.2.3 Air flowmeters. Calibrated flowmeters capable of measuring and 
monitoring air flowrates with an accuracy of <SUP>+</SUP>\2% of the 
measured flowrate.
    2.2.4 NO flowmeter. A calibrated flowmeter capable of measuring and 
monitoring NO flowrates with an accuracy of <SUP>+</SUP>\2% of the 
measured flowrate. (Rotameters have been reported to operate unreliably 
when measuring low NO flows and are not recommended.)
    2.2.5 Pressure regulator for standard NO cylinder. This regulator 
must have a non-reactive diaphragm and internal parts and a suitable 
delivery pressure.
    2.2.6 Drier. Scrubber to remove moisture from the permeation device 
air system. The use of the drier is optional with NO<INF>2</INF> 
permeation devices not sensitive to moisture. (Refer to the supplier's 
instructions for use of the permeation device.)
    2.2.7 Constant temperature chamber. Chamber capable of housing the 
NO<INF>2</INF> permeation device and maintaining its temperature to 
within <SUP>+</SUP>\0.1  deg.C.
    2.2.8 Temperature measuring device. Device capable of measuring and 
monitoring the temperature of the NO<INF>2</INF> permeation device with 
an accuracy of <SUP>+</SUP>\0.05  deg.C.
    2.2.9 Valves. A valve may be used as shown in Figure 2 to divert the 
NO<INF>2</INF> from the permeation device when zero air or NO is 
required at the manifold. A second valve may be used to divert the NO 
flow when zero air or NO<INF>2</INF> is required at the manifold.
    The valves should be constructed of glass, 
Teflon<SUP><register mark<ls-thn-eq>,</SUP> or other nonreactive 
material.
    2.2.10 Mixing chamber. A chamber constructed of glass, 
Teflon<SUP><register mark<ls-thn-eq>,</SUP> or other nonreactive 
material and designed to provide thorough mixing of pollutant gas 
streams and diluent air.
    2.2.11 Output manifold. The output manifold should be constructed of 
glass, Teflon<SUP><register mark<ls-thn-eq>,</SUP> or other non-reactive 
material and should be of sufficient diameter to insure an insignificant 
pressure drop at the analyzer connection. The system must have a vent 
designed to insure atmospheric pressure at the manifold and to prevent 
ambient air from entering the manifold.
    2.3 Reagents.
    2.3.1 Calibration standards. Calibration standards are required for 
both NO and NO<INF>2.</INF> The reference standard for the calibration 
may be either an NO or NO<INF>2</INF> standard, and must be traceable to 
a National Bureau of Standards (NBS) NO in N<INF>2</INF> Standard 
Reference Material (SRM 1683 or SRM 1684), and NBS NO<INF>2</INF> 
Standard Reference Material (SRM 1629), or an NBS/EPA-approved 
commercially

[[Page 51]]

available Certified Reference Material (CRM). CRM's are described in 
Reference 14, and a list of CRM sources is available from the address 
shown for Reference 14. Reference 15 gives recommended procedures for 
certifying an NO gas cylinder against an NO SRM or CRM and for 
certifying an NO<INF>2</INF> permeation device against an NO<INF>2</INF> 
SRM. Reference 13 contains procedures for certifying an NO gas cylinder 
against an NO<INF>2</INF> SRM and for certifying an NO<INF>2</INF> 
permeation device against an NO SRM or CRM. A procedure for determining 
the amount of NO<INF>2</INF> impurity in an NO cylinder is also 
contained in Reference 13. The NO or NO<INF>2</INF> standard selected as 
the reference standard must be used to certify the other standard to 
ensure consistency between the two standards.
    2.3.1.1 NO<INF>2</INF> Concentration standard. A permeation device 
suitable for generating NO<INF>2</INF> concentrations at the required 
flow-rates over the required concentration range. If the permeation 
device is used as the reference standard, it must be traceable to an SRM 
or CRM as specified in 2.3.1. If an NO cylinder is used as the reference 
standard, the NO<INF>2</INF> permeation device must be certified against 
the NO standard according to the procedure given in Reference 13. The 
use of the permeation device should be in strict accordance with the 
instructions supplied with the device. Additional information regarding 
the use of permeation devices is given by Scaringelli et al. (11) and 
Rook et al. (12).
    2.3.1.2 NO Concentration standard. Gas cylinder containing 50 to 100 
ppm NO in N<INF>2</INF> with less than 1 ppm NO<INF>2.</INF> If this 
cylinder is used as the reference standard, the cylinder must be 
traceable to an SRM or CRM as specified in 2.3.1. If an NO<INF>2</INF> 
permeation device is used as the reference standard, the NO cylinder 
must be certified against the NO<INF>2</INF> standard according to the 
procedure given in Reference 13. The cylinder should be recertified on a 
regular basis as determined by the local quality control program.
    2.3.3 Zero air. Air, free of contaminants which might react with NO 
or NO<INF>2</INF> or cause a detectable response on the NO/
NO<INF>X</INF>/NO<INF>2</INF> analyzer. When using permeation devices 
that are sensitive to moisture, the zero air passing across the 
permeation device must be dry to avoid surface reactions on the device. 
(Refer to the supplier's instructions for use of the permeation device.) 
A procedure for generating zero air is given in reference 13.
    2.4 Procedure.
    2.4.1 Assemble the calibration apparatus such as the typical one 
shown in Figure 2.
    2.4.2 Insure that all flowmeters are calibrated under the conditions 
of use against a reliable standard such as a soap bubble meter or wet-
test meter. All volumetric flowrates should be corrected to 25  deg.C 
and 760 mm Hg. A discussion on the calibration of flowmeters is given in 
reference 13.
    2.4.3 Install the permeation device in the constant temperature 
chamber. Provide a small fixed air flow (200-400 scm<SUP> 3</SUP>/min) 
across the device. The permeation device should always have a continuous 
air flow across it to prevent large buildup of NO<INF>2</INF> in the 
system and a consequent restabilization period. Record the flowrate as 
FP. Allow the device to stabilize at the calibration temperature for at 
least 24 hours. The temperature must be adjusted and controlled to 
within <SUP>+</SUP>\0.1  deg.C or less of the calibration temperature as 
monitored with the temperature measuring device.
    2.4.4 Precautions must be taken to remove O<INF>2</INF> and other 
contaminants from the NO pressure regulator and delivery system prior to 
the start of calibration to avoid any conversion of the standard NO to 
NO<INF>2.</INF> Failure to do so can cause significant errors in 
calibration. This problem may be minimized by
    (1) Carefully evacuating the regulator, when possible, after the 
regulator has been connected to the cylinder and before opening the 
cylinder valve;
    (2) Thoroughly flushing the regulator and delivery system with NO 
after opening the cylinder valve;
    (3) Not removing the regulator from the cylinder between 
calibrations unless absolutely necessary. Further discussion of these 
procedures is given in reference 13.
    2.4.5 Select the operating range of the NO/NO<INF>X</INF> NO<INF>2</INF> 
analyzer to be calibrated. In order to obtain maximum precision and 
accuracy for NO<INF>2</INF> calibration, all three channels of the 
analyzer should be set to the same range. If operation of the NO and 
NO<INF>X</INF> channels on higher ranges is desired, subsequent 
recalibration of the NO and NO<INF>X</INF> channels on the higher ranges 
is recommended.
    Note: Some analyzer designs may require identical ranges for NO, 
NO<INF>X,</INF> and NO<INF>2</INF> during operation of the analyzer.
    2.4.6 Connect the recorder output cable(s) of the NO/NO<INF>X</INF>/
NO<INF>2</INF> analyzer to the input terminals of the strip chart 
recorder(s). All adjustments to the analyzer should be performed based 
on the appropriate strip chart readings. References to analyzer 
responses in the procedures given below refer to recorder responses.
    2.4.7 Switch the valve to vent the flow from the permeation device 
and adjust the diluent air flowrate, F<INF>D,</INF> to provide zero air 
at the output manifold. The total air flow must exceed the total demand 
of the analyzer(s) connected to the output manifold to insure that no 
ambient air is pulled into the manifold vent. Allow the analyzer to 
sample zero air until stable NO, NO<INF>X,</INF> and NO<INF>2</INF> 
responses are obtained. After the responses have stabilized, adjust the 
analyzer zero control(s).
    Note: Some analyzers may have separate zero controls for NO, 
NO<INF>X,</INF> and NO<INF>2.</INF> Other analyzers may have separate 
zero controls only for NO and NO<INF>X,</INF> while still others may

[[Page 52]]

have only one zero common control to all three channels.
Offsetting the analyzer zero adjustments to +5% of scale is recommended 
to facilitate observing negative zero drift. Record the stable zero air 
responses as Z<INF>NO,</INF> Z<INF>NOX,</INF> and Z<INF>NO2</INF>.
    2.4.8 Preparation of NO and NO<INF>X</INF> calibration curves.
    2.4.8.1 Adjustment of NO span control. Adjust the NO flow from the 
standard NO cylinder to generate an NO concentration of approximately 
80% of the upper range limit (URL) of the NO range. The exact NO 
concentration is calculated from:
[GRAPHIC] [TIFF OMITTED] TR31AU93.049

where:

[NO]<INF>OUT</INF> = diluted NO concentration at the output manifold, 
ppm
F<INF>NO</INF> = NO flowrate, scm\3\/min
[NO]<INF>STD</INF>=concentration of the undiluted NO standard, ppm
F<INF>D</INF> = diluent air flowrate, scm<SUP> 3</SUP>/min

Sample this NO concentration until the NO and NO<INF>X</INF> responses 
have stabilized. Adjust the NO span control to obtain a recorder 
response as indicated below:

recorder response (% scale) =
[GRAPHIC] [TIFF OMITTED] TR31AU93.050

[GRAPHIC] [TIFF OMITTED] TR31AU93.051

where:

URL = nominal upper range limit of the NO channel, ppm
    Note: Some analyzers may have separate span controls for NO, 
NO<INF>X,</INF> and NO<INF>2.</INF> Other analyzers may have separate 
span controls only for NO and NO<INF>X,</INF> while still others may 
have only one span control common to all three channels. When only one 
span control is available, the span adjustment is made on the NO channel 
of the analyzer.
If substantial adjustment of the NO span control is necessary, it may be 
necessary to recheck the zero and span adjustments by repeating steps 
2.4.7 and 2.4.8.1. Record the NO concentration and the analyzer's NO 
response.
    2.4.8.2 Adjustment of NO<INF>X</INF> span control. When adjusting 
the analyzer's NO<INF>X</INF> span control, the presence of any NO<INF>2</INF> 
impurity in the standard NO cylinder must be taken into account. 
Procedures for determining the amount of NO<INF>2</INF> impurity in the 
standard NO cylinder are given in reference 13. The exact NO<INF>X</INF> 
concentration is calculated from:
[GRAPHIC] [TIFF OMITTED] TR31AU93.052

where:
[NO<INF>X</INF>]<INF>OUT</INF> = diluted NO<INF>X</INF> cencentration at 
the output manifold, ppm
[NO<INF>2</INF>]<INF>IMP</INF> = concentration of NO<INF>2</INF> 
impurity in the standard NO cylinder, ppm

Adjust the NO<INF>X</INF> span control to obtain a convenient recorder 
response as indicated below:

recorder response (% scale)
[GRAPHIC] [TIFF OMITTED] TR31AU93.053

    Note: If the analyzer has only one span control, the span adjustment 
is made on the NO channel and no further adjustment is made here for 
NO<INF>X</INF>.
If substantial adjustment of the NO<INF>X</INF> span control is 
necessary, it may be necessary to recheck the zero and span adjustments 
by repeating steps 2.4.7 and 2.4.8.2. Record the NO<INF>X</INF> 
concentration and the analyzer's NO<INF>X</INF> response.
    2.4.8.3 Generate several additional concentrations (at least five 
evenly spaced points across the remaining scale are suggested to verify 
linearity) by decreasing F<INF>NO</INF> or increasing F<INF>D.</INF> For 
each concentration generated, calculate the exact NO and NO<INF>X</INF> 
concentrations using equations (16) and (18) respectively. Record the 
analyzer's NO and NO<INF>X</INF> responses for each concentration. Plot 
the analyzer responses versus the respective calculated NO and NO<INF>X</INF> 
concentrations and draw or calculate the NO and NO<INF>X</INF> 
calibration curves. For subsequent calibrations where linearity can be 
assumed, these curves may be checked with a two-point calibration 
consisting of a zero point and NO and NO<INF>X</INF> concentrations of 
approximately 80 percent of the URL.
    2.4.9 Preparation of NO<INF>2</INF> calibration curve.
    2.4.9.1 Remove the NO flow. Assuming the NO<INF>2</INF> zero has 
been properly adjusted while sampling zero air in step 2.4.7, switch the 
valve to provide NO<INF>2</INF> at the output manifold.
    2.4.9.2 Adjust F<INF>D</INF> to generate an NO<INF>2</INF> 
concentration of approximately 80 percent of the URL of the NO<INF>2</INF> 
range. The total air flow must exceed the demand of the analyzer(s) 
under calibration. The actual concentration of NO<INF>2</INF> is 
calculated from:
[GRAPHIC] [TIFF OMITTED] TR31AU93.054

where:

[NO<INF>2</INF>]<INF>OUT</INF> = diluted NO<INF>2</INF> concentration at 
the output manifold, ppm
R = permeation rate, <<SUP>greek</SUP> muls-thn-eq</SUP>g/min

[[Page 53]]

K = 0.532<<SUP>greek</SUP> muls-thn-eq</SUP>l NO<INF>2</INF>/<<SUP>greek</SUP> 
muls-thn-eq</SUP>g NO<INF>2</INF> (at 25  deg.C and 760 mm Hg)
F<INF>p</INF> = air flowrate across permeation device, scm<SUP> 3</SUP>/
min
F<INF>D</INF> = diluent air flowrate, scm<SUP> 3</SUP>/min

Sample this NO<INF>2</INF> concentration until the NO<INF>X</INF> and 
NO<INF>2</INF> responses have stabilized. Adjust the NO<INF>2</INF> span 
control to obtain a recorder response as indicated below:

recorder response (% scale)
[GRAPHIC] [TIFF OMITTED] TR31AU93.055

    Note: If the analyzer has only one or two span controls, the span 
adjustments are made on the NO channel or NO and NO<INF>X</INF> channels 
and no further adjustment is made here for NO<INF>2</INF>.

If substantial adjustment of the NO<INF>2</INF> span control is 
necessary it may be necessary to recheck the zero and span adjustments 
by repeating steps 2.4.7 and 2.4.9.2. Record the NO<INF>2</INF> 
concentration and the analyzer's NO<INF>2</INF> response. Using the 
NO<INF>X</INF> calibration curve obtained in step 2.4.8, measure and 
record the NO<INF>X</INF> concentration as [NO<INF>X</INF>]<INF>M</INF>.
    2.4.9.3 Adjust F<INF>D</INF> to obtain several other concentrations 
of NO<INF>2</INF> over the NO<INF>2</INF> range (at least five evenly 
spaced points across the remaining scale are suggested). Calculate each 
NO<INF>2</INF> concentration using equation (20) and record the 
corresponding analyzer NO<INF>2</INF> and NO<INF>X</INF> responses. Plot 
the analyzer's NO<INF>2</INF> responses versus the corresponding 
calculated NO<INF>2</INF> concentrations and draw or calculate the 
NO<INF>2</INF> calibration curve.
    2.4.10 Determination of converter efficiency.
    2.4.10.1 Plot [NO<INF>X</INF>]<INF>M</INF> (y-axis) versus 
[NO<INF>2</INF>]<INF>OUT</INF> (x-axis) and draw or calculate the 
converter efficiency curve. The slope of the curve times 100 is the 
average converter efficiency, E<INF>C.</INF> The average converter 
efficiency must be greater than 96 percent; if it is less than 96 
percent, replace or service the converter.
    Note: Supplemental information on calibration and other procedures 
in this method are given in reference 13.
    3. Frequency of calibration. The frequency of calibration, as well 
as the number of points necessary to establish the calibration curve and 
the frequency of other performance checks, will vary from one analyzer 
to another. The user's quality control program should provide guidelines 
for initial establishment of these variables and for subsequent 
alteration as operational experience is accumulated. Manufacturers of 
analyzers should include in their instruction/operation manuals 
information and guidance as to these variables and on other matters of 
operation, calibration, and quality control.

                               References

    1. A. Fontijn, A. J. Sabadell, and R. J. Ronco, ``Homogeneous 
Chemiluminescent Measurement of Nitric Oxide with Ozone,'' Anal. Chem., 
42, 575 (1970).
    2. D. H. Stedman, E. E. Daby, F. Stuhl, and H. Niki, ``Analysis of 
Ozone and Nitric Oxide by a Chemiluminiscent Method in Laboratory and 
Atmospheric Studies of Photochemical Smog,'' J. Air Poll. Control 
Assoc., 22, 260 (1972).
    3. B. E. Martin, J. A. Hodgeson, and R. K. Stevens, ``Detection of 
Nitric Oxide Chemiluminescence at Atmospheric Pressure,'' Presented at 
164th National ACS Meeting, New York City, August 1972.
    4. J. A. Hodgeson, K. A. Rehme, B. E. Martin, and R. K. Stevens, 
``Measurements for Atmospheric Oxides of Nitrogen and Ammonia by 
Chemiluminescence,'' Presented at 1972 APCA Meeting, Miami, FL, June 
1972.
    5. R. K. Stevens and J. A. Hodgeson, ``Applications of 
Chemiluminescence Reactions to the Measurement of Air Pollutants,'' 
Anal. Chem., 45, 443A (1973).
    6. L. P. Breitenbach and M. Shelef, ``Development of a Method for 
the Analysis of NO<INF>2</INF> and NH<INF>3</INF> by NO-Measuring 
Instruments,'' J. Air Poll. Control Assoc., 23, 128 (1973).
    7. A. M. Winer, J. W. Peters, J. P. Smith, and J. N. Pitts, Jr., 
``Response of Commercial Chemiluminescent NO-NO<INF>2</INF> Analyzers to 
Other Nitrogen-Containing Compounds,'' Environ. Sci. Technol., 8, 1118 
(1974).
    8. K. A. Rehme, B. E. Martin, and J. A. Hodgeson, Tentative Method 
for the Calibration of Nitric Oxide, Nitrogen Dioxide, and Ozone 
Analyzers by Gas Phase Titration,'' EPA-R2-73-246, March 1974.
    9. J. A. Hodgeson, R. K. Stevens, and B. E. Martin, ``A Stable Ozone 
Source Applicable as a Secondary Standard for Calibration of Atmospheric 
Monitors,'' ISA Transactions, 11, 161 (1972).
    10. A. E. O'Keeffe and G. C. Ortman, ``Primary Standards for Trace 
Gas Analysis,'' Anal. Chem., 38, 760 (1966).
    11. F. P. Scaringelli, A. E. O'Keeffe, E. Rosenberg, and J. P. Bell, 
``Preparation of Known Concentrations of Gases and Vapors with 
Permeation Devices Calibrated Gravimetrically,'' Anal. Chem., 42, 871 
(1970).
    12. H. L. Rook, E. E. Hughes, R. S. Fuerst, and J. H. Margeson, 
``Operation Characteristics of NO<INF>2</INF> Permeation Devices,'' 
Presented at 167th National ACS Meeting, Los Angeles, CA, April 1974.
    13. E. C. Ellis, ``Technical Assistance Document for the 
Chemiluminescence Measurement of Nitrogen Dioxide,'' EPA-E600/4-75-003 
(Available in draft form from the United States Environmental Protection 
Agency, Department E (MD-76), Environmental Monitoring and Support 
Laboratory, Research Triangle Park, NC 27711).

[[Page 54]]

    14. A Procedure for Establishing Traceability of Gas Mixtures to 
Certain National Bureau of Standards Standard Reference Materials. EPA-
600/7-81-010, Joint publication by NBS and EPA. Available from the U.S. 
Environmental Protection Agency, Environmental Monitoring Systems 
Laboratory (MD-77), Research Triangle Park, NC 27711, May 1981.
    15. Quality Assurance Handbook for Air Pollution Measurement 
Systems, Volume II, Ambient Air Specific Methods. The U.S. Environmental 
Protection Agency, Environmental Monitoring Systems Laboratory, Research 
Triangle Park, NC 27711. Publication No. EAP-600/4-77-027a.
<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

[[Page 55]]

<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

[41 FR 52688, Dec. 1, 1976, as amended at 48 FR 2529, Jan 20, 1983]

Appendix G to Part 50--Reference Method for the Determination of Lead in 
         Suspended Particulate Matter Collected From Ambient Air

    1. Principle and applicability.
    1.1 Ambient air suspended particulate matter is collected on a 
glass-fiber filter for 24 hours using a high volume air sampler. The 
analysis of the 24-hour samples may be performed for either individual 
samples or composites of the samples collected over a calendar month or 
quarter, provided that the compositing procedure has been approved in 
accordance with section 2.8 of appendix C to part 58 of this chapter--
Modifications of methods by users. (Guidance or assistance in requesting 
approval under Section 2.8 can be obtained from the address given in 
section 2.7 of appendix C to part 58 of this chapter.)
    1.2 Lead in the particulate matter is solubilized by extraction with 
nitric acid (HNO<INF>3</INF>), facilitated by heat or by a mixture of 
HNO<INF>3</INF> and hydrochloric acid (HCl) facilitated by 
ultrasonication.
    1.3 The lead content of the sample is analyzed by atomic absorption 
spectrometry using an air-acetylene flame, the 283.3 or 217.0 nm lead 
absorption line, and the optimum instrumental conditions recommended by 
the manufacturer.
    1.4 The ultrasonication extraction with HNO<INF>3</INF>/HCl will 
extract metals other than lead from ambient particulate matter.
    2. Range, sensitivity, and lower detectable limit. The values given 
below are typical of the methods capabilities. Absolute values will vary 
for individual situations depending on the type of instrument used, the 
lead line, and operating conditions.
    2.1 Range. The typical range of the method is 0.07 to 7.5 
<<SUP>greek</SUP> muls-thn-eq</SUP>g Pb/m\3\ assuming an upper linear 
range of analysis of 15 <<SUP>greek</SUP> muls-thn-eq</SUP>g/ml and an 
air volume of 2,400 m\3\.
    2.2 Sensitivity. Typical sensitivities for a 1 percent change in 
absorption (0.0044 absorbance units) are 0.2 and 0.5 <<SUP>greek</SUP> 
muls-thn-eq</SUP>g Pb/ml for the 217.0 and 283.3 nm lines, respectively.
    2.3 Lower detectable limit (LDL). A typical LDL is 0.07 <<SUP>greek</SUP> 
muls-thn-eq</SUP>g Pb/m\3\. The above value was calculated by doubling 
the between-laboratory standard deviation obtained for the lowest 
measurable lead concentration in a collaborative test of the method.(15) 
An air volume of 2,400 m\3\ was assumed.
    3. Interferences. Two types of interferences are possible: chemical 
and light scattering.
    3.1 Chemical. Reports on the absence (1, 2, 3, 4, 5) of chemical 
interferences far outweigh those reporting their presence, (6) 
therefore, no correction for chemical interferences is given here. If 
the analyst suspects that the sample matrix is causing a chemical 
interference, the interference can be verified and corrected for by 
carrying out the analysis with and without the method of standard 
additions.(7)

[[Page 56]]

    3.2 Light scattering. Nonatomic absorption or light scattering, 
produced by high concentrations of dissolved solids in the sample, can 
produce a significant interference, especially at low lead 
concentrations. (2) The interference is greater at the 217.0 nm line 
than at the 283.3 nm line. No interference was observed using the 283.3 
nm line with a similar method.(1)
    Light scattering interferences can, however, be corrected for 
instrumentally. Since the dissolved solids can vary depending on the 
origin of the sample, the correction may be necessary, especially when 
using the 217.0 nm line. Dual beam instruments with a continuum source 
give the most accurate correction. A less accurate correction can be 
obtained by using a nonabsorbing lead line that is near the lead 
analytical line. Information on use of these correction techniques can 
be obtained from instrument manufacturers' manuals.
    If instrumental correction is not feasible, the interference can be 
eliminated by use of the ammonium pyrrolidinecarbodithioate-
methylisobutyl ketone, chelation-solvent extraction technique of sample 
preparation.(8)
    4. Precision and bias.
    4.1 The high-volume sampling procedure used to collect ambient air 
particulate matter has a between-laboratory relative standard deviation 
of 3.7 percent over the range 80 to 125 <<SUP>greek</SUP> 
muls-thn-eq</SUP>g/m\3\.(9) The combined extraction-analysis procedure 
has an average within-laboratory relative standard deviation of 5 to 6 
percent over the range 1.5 to 15 <<SUP>greek</SUP> muls-thn-eq</SUP>g 
Pb/ml, and an average between laboratory relative standard deviation of 
7 to 9 percent over the same range. These values include use of either 
extraction procedure.
    4.2 Single laboratory experiments and collaborative testing indicate 
that there is no significant difference in lead recovery between the hot 
and ultrasonic extraction procedures.(15)
    5. Apparatus.
    5.1 Sampling.
    5.1.1 High-Volume Sampler. Use and calibrate the sampler as 
described in appendix B to this part.
    5.2 Analysis.
    5.2.1 Atomic absorption spectrophotometer. Equipped with lead hollow 
cathode or electrodeless discharge lamp.
    5.2.1.1 Acetylene. The grade recommended by the instrument 
manufacturer should be used. Change cylinder when pressure drops below 
50-100 psig.
    5.2.1.2 Air. Filtered to remove particulate, oil, and water.
    5.2.2 Glassware. Class A borosilicate glassware should be used 
throughout the analysis.
    5.2.2.1 Beakers. 30 and 150 ml. graduated, Pyrex.
    5.2.2.2 Volumetric flasks. 100-ml.
    5.2.2.3 Pipettes. To deliver 50, 30, 15, 8, 4, 2, 1 ml.
    5.2.2.4 Cleaning. All glassware should be scrupulously cleaned. The 
following procedure is suggested. Wash with laboratory detergent, rinse, 
soak for 4 hours in 20 percent (w/w) HNO<INF>3,</INF> rinse 3 times with 
distilled-deionized water, and dry in a dust free manner.
    5.2.3 Hot plate.
    5.2.4. Ultrasonication water bath, unheated. Commercially available 
laboratory ultrasonic cleaning baths of 450 watts or higher ``cleaning 
power,'' i.e., actual ultrasonic power output to the bath have been 
found satisfactory.
    5.2.5 Template. To aid in sectioning the glass-fiber filter. See 
figure 1 for dimensions.
    5.2.6 Pizza cutter. Thin wheel. Thickness 1mm.
    5.2.7 Watch glass.
    5.2.8 Polyethylene bottles. For storage of samples. Linear 
polyethylene gives better storage stability than other polyethylenes and 
is preferred.
    5.2.9 Parafilm ``M''.\1\ American Can Co., Marathon Products, 
Neenah, Wis., or equivalent.
---------------------------------------------------------------------------

    \1\ Mention of commercial products does not imply endorsement by the 
U.S. Environmental Protection Agency.
---------------------------------------------------------------------------

    6. Reagents.
    6.1 Sampling.
    6.1.1 Glass fiber filters. The specifications given below are 
intended to aid the user in obtaining high quality filters with 
reproducible properties. These specifications have been met by EPA 
contractors.
    6.1.1.1 Lead content. The absolute lead content of filters is not 
critical, but low values are, of course, desirable. EPA typically 
obtains filters with a lead content of 75 <<SUP>greek</SUP> 
muls-thn-eq</SUP>g/filter.
    It is important that the variation in lead content from filter to 
filter, within a given batch, be small.
    6.1.1.2 Testing.
    6.1.1.2.1 For large batches of filters (<ls-thn-eq>500 filters) 
select at random 20 to 30 filters from a given batch. For small batches 
(<ls-thn-eq>500 filters) a lesser number of filters may be taken. Cut 
one \3/4\``x8`` strip from each filter anywhere in the filter. Analyze 
all strips, separately, according to the directions in sections 7 and 8.
    6.1.1.2.2 Calculate the total lead in each filter as
    [GRAPHIC] [TIFF OMITTED] TC08NO91.084
    
where:

F<INF>b</INF> = Amount of lead per 72 square inches of filter, 
<<SUP>greek</SUP> muls-thn-eq</SUP>g.

    6.1.1.2.3 Calculate the mean, F<INF>b,</INF> of the values and the 
relative standard deviation (standard deviation/mean x 100). If the 
relative standard deviation is high enough so

[[Page 57]]

that, in the analysts opinion, subtraction of F<INF>b,</INF> (section 
10.3) may result in a significant error in the <<SUP>greek</SUP> 
muls-thn-eq</SUP>g Pb/m\3,\ the batch should be rejected.
    6.1.1.2.4 For acceptable batches, use the value of F<INF>b</INF> to 
correct all lead analyses (section 10.3) of particulate matter collected 
using that batch of filters. If the analyses are below the LDL (section 
2.3) no correction is necessary.
    6.2 Analysis.
    6.2.1 Concentrated (15.6 M) HNO<INF>3.</INF> ACS reagent grade 
HNO<INF>3</INF> and commercially available redistilled HNO<INF>3</INF> 
has found to have sufficiently low lead concentrations.
    6.2.2 Concentrated (11.7 M) HCl. ACS reagent grade.
    6.2.3 Distilled-deionized water. (D.I. water).
    6.2.4 3 M HNO<INF>3.</INF> This solution is used in the hot 
extraction procedure. To prepare, add 192 ml of concentrated HNO<INF>3</INF> 
to D.I. water in a 1 l volumetric flask. Shake well, cool, and dilute to 
volume with D.I. water. Caution: Nitric acid fumes are toxic. Prepare in 
a well ventilated fume hood.
    6.2.5 0.45 M HNO<INF>3.</INF> This solution is used as the matrix 
for calibration standards when using the hot extraction procedure. To 
prepare, add 29 ml of concentrated HNO<INF>3</INF> to D.I. water in a 1 
l volumetric flask. Shake well, cool, and dilute to volume with D.I. 
water.
    6.2.6 2.6 M HNO<INF>3</INF>+0 to 0.9 M HCl. This solution is used in 
the ultrasonic extraction procedure. The concentration of HCl can be 
varied from 0 to 0.9 M. Directions are given for preparation of a 2.6 M 
HNO<INF>3</INF>+0.9 M HCl solution. Place 167 ml of concentrated 
HNO<INF>3</INF> into a 1 l volumetric flask and add 77 ml of 
concentrated HCl. Stir 4 to 6 hours, dilute to nearly 1 l with D.I. 
water, cool to room temperature, and dilute to 1 l.
    6.2.7 0.40 M HNO<INF>3</INF> + X M HCl. This solution is used as the 
matrix for calibration standards when using the ultrasonic extraction 
procedure. To prepare, add 26 ml of concentrated HNO<INF>3,</INF> plus 
the ml of HCl required, to a 1 l volumetric flask. Dilute to nearly 1 l 
with D.I. water, cool to room temperature, and dilute to 1 l. The amount 
of HCl required can be determined from the following equation:
[GRAPHIC] [TIFF OMITTED] TC08NO91.085

where:

y = ml of concentrated HCl required.
x = molarity of HCl in 6.2.6.
0.15 = dilution factor in 7.2.2.

    6.2.8 Lead nitrate, Pb(NO<INF>3</INF>)<INF>2.</INF> ACS reagent 
grade, purity 99.0 percent. Heat for 4 hours at 120  deg.C and cool in a 
desiccator.
    6.3 Calibration standards.
    6.3.1 Master standard, 1000 <<SUP>greek</SUP> muls-thn-eq</SUP>g Pb/
ml in HNO<INF>3.</INF> Dissolve 1.598 g of Pb(NO<INF>3</INF>)<INF>2</INF> 
in 0.45 M HNO<INF>3</INF> contained in a 1 l volumetric flask and dilute 
to volume with 0.45 M HNO<INF>3</INF>.
    6.3.2 Master standard, 1000 <<SUP>greek</SUP> muls-thn-eq</SUP>g Pb/
ml in HNO<INF>3</INF>/HCl. Prepare as in section 6.3.1 except use the 
HNO<INF>3</INF>/HCl solution in section 6.2.7.
    Store standards in a polyethylene bottle. Commercially available 
certified lead standard solutions may also be used.
    7. Procedure.
    7.1 Sampling. Collect samples for 24 hours using the procedure 
described in reference 10 with glass-fiber filters meeting the 
specifications in section 6.1.1. Transport collected samples to the 
laboratory taking care to minimize contamination and loss of sample. 
(16).
    7.2 Sample preparation.
    7.2.1 Hot extraction procedure.
    7.2.1.1 Cut a \3/4\``x8`` strip from the exposed filter using a 
template and a pizza cutter as described in Figures 1 and 2. Other 
cutting procedures may be used.
    Lead in ambient particulate matter collected on glass fiber filters 
has been shown to be uniformly distributed across the 
filter.<SUP>1, 3, 11</SUP> Another study \12\ has shown that when 
sampling near a roadway, strip position contributes significantly to the 
overall variability associated with lead analyses. Therefore, when 
sampling near a roadway, additional strips should be analyzed to 
minimize this variability.
    7.2.1.2 Fold the strip in half twice and place in a 150-ml beaker. 
Add 15 ml of 3 M HNO<INF>3</INF> to cover the sample. The acid should 
completely cover the sample. Cover the beaker with a watch glass.
    7.2.1.3 Place beaker on the hot-plate, contained in a fume hood, and 
boil gently for 30 min. Do not let the sample evaporate to dryness. 
Caution: Nitric acid fumes are toxic.
    7.2.1.4 Remove beaker from hot plate and cool to near room 
temperature.
    7.2.1.5 Quantitatively transfer the sample as follows:
    7.2.1.5.1 Rinse watch glass and sides of beaker with D.I. water.
    7.2.1.5.2 Decant extract and rinsings into a 100-ml volumetric 
flask.
    7.2.1.5.3 Add D.I. water to 40 ml mark on beaker, cover with watch 
glass, and set aside for a minimum of 30 minutes. This is a critical 
step and cannot be omitted since it allows the HNO<INF>3</INF> trapped 
in the filter to diffuse into the rinse water.
    7.2.1.5.4 Decant the water from the filter into the volumetric 
flask.
    7.2.1.5.5 Rinse filter and beaker twice with D.I. water and add 
rinsings to volumetric flask until total volume is 80 to 85 ml.
    7.2.1.5.6 Stopper flask and shake vigorously. Set aside for 
approximately 5 minutes or until foam has dissipated.
    7.2.1.5.7 Bring solution to volume with D.I. water. Mix thoroughly.
    7.2.1.5.8 Allow solution to settle for one hour before proceeding 
with analysis.

[[Page 58]]

    7.2.1.5.9 If sample is to be stored for subsequent analysis, 
transfer to a linear polyethylene bottle.
    7.2.2 Ultrasonic extraction procedure.
    7.2.2.1 Cut a \3/4\``x8`` strip from the exposed filter as described 
in section 7.2.1.1.
    7.2.2.2 Fold the strip in half twice and place in a 30 ml beaker. 
Add 15 ml of the HNO<INF>3</INF>/HCl solution in section 6.2.6. The acid 
should completely cover the sample. Cover the beaker with parafilm.
    The parafilm should be placed over the beaker such that none of the 
parafilm is in contact with water in the ultrasonic bath. Otherwise, 
rinsing of the parafilm (section 7.2.2.4.1) may contaminate the sample.
    7.2.2.3 Place the beaker in the ultrasonication bath and operate for 
30 minutes.
    7.2.2.4 Quantitatively transfer the sample as follows:
    7.2.2.4.1 Rinse parafilm and sides of beaker with D.I. water.
    7.2.2.4.2 Decant extract and rinsings into a 100 ml volumetric 
flask.
    7.2.2.4.3 Add 20 ml D.I. water to cover the filter strip, cover with 
parafilm, and set aside for a minimum of 30 minutes. This is a critical 
step and cannot be omitted. The sample is then processed as in sections 
7.2.1.5.4 through 7.2.1.5.9.
    Note: Samples prepared by the hot extraction procedure are now in 
0.45 M HNO<INF>3.</INF> Samples prepared by the ultrasonication 
procedure are in 0.40 M HNO<INF>3</INF> + X M HCl.
    8. Analysis.
    8.1 Set the wavelength of the monochromator at 283.3 or 217.0 nm. 
Set or align other instrumental operating conditions as recommended by 
the manufacturer.
    8.2 The sample can be analyzed directly from the volumetric flask, 
or an appropriate amount of sample decanted into a sample analysis tube. 
In either case, care should be taken not to disturb the settled solids.
    8.3 Aspirate samples, calibration standards and blanks (section 9.2) 
into the flame and record the equilibrium absorbance.
    8.4 Determine the lead concentration in <<SUP>greek</SUP> 
muls-thn-eq</SUP>g Pb/ml, from the calibration curve, section 9.3.
    8.5 Samples that exceed the linear calibration range should be 
diluted with acid of the same concentration as the calibration standards 
and reanalyzed.
    9. Calibration.
    9.1 Working standard, 20 <<SUP>greek</SUP> muls-thn-eq</SUP>g Pb/ml. 
Prepared by diluting 2.0 ml of the master standard (section 6.3.1 if the 
hot acid extraction was used or section 6.3.2 if the ultrasonic 
extraction procedure was used) to 100 ml with acid of the same 
concentration as used in preparing the master standard.
    9.2 Calibration standards. Prepare daily by diluting the working 
standard, with the same acid matrix, as indicated below. Other lead 
concentrations may be used.

------------------------------------------------------------------------
                                                           Concentration
    Volume of 20 <greek mu<ls-thn-eq>g/ml        Final     <greek mu<ls-
            working standard, ml              volume, ml  thn-eq>g Pb/ml

------------------------------------------------------------------------
0...........................................         100             0
1.0.........................................         200           0.1
2.0.........................................         200           0.2
2.0.........................................         100           0.4
4.0.........................................         100           0.8
8.0.........................................         100           1.6
15.0........................................         100           3.0
30.0........................................         100           6.0
50.0........................................         100          10.0
100.0.......................................         100          20.0
------------------------------------------------------------------------

    9.3 Preparation of calibration curve. Since the working range of 
analysis will vary depending on which lead line is used and the type of 
instrument, no one set of instructions for preparation of a calibration 
curve can be given. Select standards (plus the reagent blank), in the 
same acid concentration as the samples, to cover the linear absorption 
range indicated by the instrument manufacturer. Measure the absorbance 
of the blank and standards as in section 8.0. Repeat until good 
agreement is obtained between replicates. Plot absorbance (y-axis) 
versus concentration in <<SUP>greek</SUP> muls-thn-eq</SUP>g Pb/ml (x-
axis). Draw (or compute) a straight line through the linear portion of 
the curve. Do not force the calibration curve through zero. Other 
calibration procedures may be used.
    To determine stability of the calibration curve, remeasure--
alternately--one of the following calibration standards for every 10th 
sample analyzed: Concentration  1<<SUP>greek</SUP> muls-thn-eq</SUP>g 
Pb/ml; concentration  10 <<SUP>greek</SUP> muls-thn-eq</SUP>g Pb/ml. If 
either standard deviates by more than 5 percent from the value predicted 
by the calibration curve, recalibrate and repeat the previous 10 
analyses.
    10. Calculation.
    10.1 Measured air volume. Calculate the measured air volume at 
Standard Temperature and Pressure as described in Reference 10.
    10.2 Lead concentration. Calculate lead concentration in the air 
sample.
<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

[[Page 59]]

where:

C = Concentration, <<SUP>greek</SUP> muls-thn-eq</SUP>g Pb/sm\3\.
<<SUP>greek</SUP> muls-thn-eq</SUP>g Pb/ml = Lead concentration 
determined from section 8.
100 ml/strip = Total sample volume.
12 strips = Total useable filter area, 8``;x9``;. Exposed area of one 
strip, \3/4\``;x7``;.
Filter = Total area of one strip, \3/4\``;x8``;.
F<INF>b</INF> = Lead concentration of blank filter, <<SUP>greek</SUP> 
muls-thn-eq</SUP>g, from section 6.1.1.2.3.
V<INF>STP</INF> = Air volume from section 10.2.

    11. Quality control.
    \3/4\``;x8``; glass fiber filter strips containing 80 to 2000 
<<SUP>greek</SUP> muls-thn-eq</SUP>g Pb/strip (as lead salts) and blank 
strips with zero Pb content should be used to determine if the method--
as being used--has any bias. Quality control charts should be 
established to monitor differences between measured and true values. The 
frequency of such checks will depend on the local quality control 
program.
    To minimize the possibility of generating unreliable data, the user 
should follow practices established for assuring the quality of air 
pollution data, (13) and take part in EPA's semiannual audit program for 
lead analyses.
    12. Trouble shooting.
    1. During extraction of lead by the hot extraction procedure, it is 
important to keep the sample covered so that corrosion products--formed 
on fume hood surfaces which may contain lead--are not deposited in the 
extract.
    2. The sample acid concentration should minimize corrosion of the 
nebulizer. However, different nebulizers may require lower acid 
concentrations. Lower concentrations can be used provided samples and 
standards have the same acid concentration.
    3. Ashing of particulate samples has been found, by EPA and 
contractor laboratories, to be unnecessary in lead analyses by atomic 
absorption. Therefore, this step was omitted from the method.
    4. Filtration of extracted samples, to remove particulate matter, 
was specifically excluded from sample preparation, because some analysts 
have observed losses of lead due to filtration.
    5. If suspended solids should clog the nebulizer during analysis of 
samples, centrifuge the sample to remove the solids.
    13. Authority.
    (Secs. 109 and 301(a), Clean Air Act, as amended (42 U.S.C. 7409, 
7601(a)))
    14. References.
    1. Scott, D. R. et al. ``Atomic Absorption and Optical Emission 
Analysis of NASN Atmospheric Particulate Samples for Lead.'' Envir. Sci. 
and Tech., 10, 877-880 (1976).
    2. Skogerboe, R. K. et al. ``Monitoring for Lead in the 
Environment.'' pp. 57-66, Department of Chemistry, Colorado State 
University, Fort Collins, CO 80523. Submitted to National Science 
Foundation for publications, 1976.
    3. Zdrojewski, A. et al. ``The Accurate Measurement of Lead in 
Airborne Particulates.'' Inter. J. Environ. Anal. Chem., 2, 63-77 
(1972).
    4. Slavin, W., ``Atomic Absorption Spectroscopy.'' Published by 
Interscience Company, New York, NY (1968).
    5. Kirkbright, G. F., and Sargent, M., ``Atomic Absorption and 
Fluorescence Spectroscopy.'' Published by Academic Press, New York, NY 
1974.
    6. Burnham, C. D. et al., ``Determination of Lead in Airborne 
Particulates in Chicago and Cook County, IL, by Atomic Absorption 
Spectroscopy.'' Envir. Sci. and Tech., 3, 472-475 (1969).
    7. ``Proposed Recommended Practices for Atomic Absorption 
Spectrometry.'' ASTM Book of Standards, part 30, pp. 1596-1608 (July 
1973).
    8. Koirttyohann, S. R. and Wen, J. W., ``Critical Study of the APCD-
MIBK Extraction System for Atomic Absorption.'' Anal. Chem., 45, 1986-
1989 (1973).
    9. Collaborative Study of Reference Method for the Determination of 
Suspended Particulates in the Atmosphere (High Volume Method). 
Obtainable from National Technical Information Service, Department of 
Commerce, Port Royal Road, Springfield, VA 22151, as PB-205-891.
    10. [Reserved]
    11. Dubois, L., et al., ``The Metal Content of Urban Air.'' JAPCA, 
16, 77-78 (1966).
    12. EPA Report No. 600/4-77-034, June 1977, ``Los Angeles Catalyst 
Study Symposium.'' Page 223.
    13. Quality Assurance Handbook for Air Pollution Measurement System. 
Volume 1--Principles. EPA-600/9-76-005, March 1976.
    14. Thompson, R. J. et al., ``Analysis of Selected Elements in 
Atmospheric Particulate Matter by Atomic Absorption.'' Atomic Absorption 
Newsletter, 9, No. 3, May-June 1970.
    15. To be published. EPA, QAB, EMSL, RTP, N.C. 27711
    16. Quality Assurance Handbook for Air Pollution Measurement 
Systems. Volume II--Ambient Air Specific Methods. EPA-600/4-77/027a, May 
1977.

[[Page 60]]

<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

[[Page 61]]

<GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT>

(Secs. 109, 301(a) of the Clean Air Act, as amended (42 U.S.C. 7409, 
7601(a)); secs. 110, 301(a) and 319 of the Clean Air Act (42 U.S.C. 
7410, 7601(a), 7619))
[43 FR 46258, Oct. 5, 1978; 44 FR 37915, June 29, 1979, as amended at 46 
FR 44163, Sept. 3, 1981; 52 FR 24664, July 1, 1987]

[[Page 62]]

    Appendix H to Part 50--Interpretation of the 1-Hour Primary and 
       Secondary National Ambient Air Quality Standards for Ozone

                               1. General

    This appendix explains how to determine when the expected number of 
days per calendar year with maximum hourly average concentrations above 
0.12 ppm (235 <<SUP>greek</SUP> muls-thn-eq</SUP>g/m\3\) is equal to or 
less than 1. An expanded discussion of these procedures and associated 
examples are contained in the ``Guideline for Interpretation of Ozone 
Air Quality Standards.'' For purposes of clarity in the following 
discussion, it is convenient to use the term ``exceedance'' to describe 
a daily maximum hourly average ozone measurement that is greater than 
the level of the standard. Therefore, the phrase ``expected number of 
days with maximum hourly average ozone concentrations above the level of 
the standard'' may be simply stated as the ``expected number of 
exceedances.''
    The basic principle in making this determination is relatively 
straightforward. Most of the complications that arise in determining the 
expected number of annual exceedances relate to accounting for 
incomplete sampling. In general, the average number of exceedances per 
calendar year must be less than or equal to 1. In its simplest form, the 
number of exceedances at a monitoring site would be recorded for each 
calendar year and then averaged over the past 3 calendar years to 
determine if this average is less than or equal to 1.

                2. Interpretation of Expected Exceedances

    The ozone standard states that the expected number of exceedances 
per year must be less than or equal to 1. The statistical term 
``expected number'' is basically an arithmetic average. The following 
example explains what it would mean for an area to be in compliance with 
this type of standard. Suppose a monitoring station records a valid 
daily maximum hourly average ozone value for every day of the year 
during the past 3 years. At the end of each year, the number of days 
with maximum hourly concentrations above 0.12 ppm is determined and this 
number is averaged with the results of previous years. As long as this 
average remains ``less than or equal to 1,'' the area is in compliance.

           3. Estimating the Number of Exceedances for a Year

    In general, a valid daily maximum hourly average value may not be 
available for each day of the year, and it will be necessary to account 
for these missing values when estimating the number of exceedances for a 
particular calendar year. The purpose of these computations is to 
determine if the expected number of exceedances per year is less than or 
equal to 1. Thus, if a site has two or more observed exceedances each 
year, the standard is not met and it is not necessary to use the 
procedures of this section to account for incomplete sampling.
    The term ``missing value'' is used here in the general sense to 
describe all days that do not have an associated ozone measurement. In 
some cases, a measurement might actually have been missed but in other 
cases no measurement may have been scheduled for that day. A daily 
maximum ozone value is defined to be the highest hourly ozone value 
recorded for the day. This daily maximum value is considered to be valid 
if 75 percent of the hours from 9:01 a.m. to 9:00 p.m. (LST) were 
measured or if the highest hour is greater than the level of the 
standard.
    In some areas, the seasonal pattern of ozone is so pronounced that 
entire months need not be sampled because it is extremely unlikely that 
the standard would be exceeded. Any such waiver of the ozone monitoring 
requirement would be handled under provisions of 40 CFR, part 58. Some 
allowance should also be made for days for which valid daily maximum 
hourly values were not obtained but which would quite likely have been 
below the standard. Such an allowance introduces a complication in that 
it becomes necessary to define under what conditions a missing value may 
be assumed to have been less than the level of the standard. The 
following criterion may be used for ozone:
    A missing daily maximum ozone value may be assumed to be less than 
the level of the standard if the valid daily maxima on both the 
preceding day and the following day do not exceed 75 percent of the 
level of the standard.
    Let z denote the number of missing daily maximum values that may be 
assumed to be less than the standard. Then the following formula shall 
be used to estimate the expected number of exceedances for the year:
[GRAPHIC] [TIFF OMITTED] TC08NO91.086

    (*Indicates multiplication.)

where:

e = the estimated number of exceedances for the year,
N = the number of required monitoring days in the year,
n = the number of valid daily maxima,
v = the number of daily values above the level of the standard, and
z = the number of days assumed to be less than the standard level.

    This estimated number of exceedances shall be rounded to one decimal 
place (fractional parts equal to 0.05 round up).

[[Page 63]]

    It should be noted that N will be the total number of days in the 
year unless the appropriate Regional Administrator has granted a waiver 
under the provisions of 40 CFR part 58.
    The above equation may be interpreted intuitively in the following 
manner. The estimated number of exceedances is equal to the observed 
number of exceedances (v) plus an increment that accounts for incomplete 
sampling. There were (N-n) missing values for the year but a certain 
number of these, namely z, were assumed to be less than the standard. 
Therefore, (N-n-z) missing values are considered to include possible 
exceedances. The fraction of measured values that are above the level of 
the standard is v/n. It is assumed that this same fraction applies to 
the (N-n-z) missing values and that (v/n)*(N-n-z) of these values would 
also have exceeded the level of the standard.

[44 FR 8220, Feb. 8, 1979, as amended at 62 FR 38895, July 18, 1997]

    Appendix I to Part 50--Interpretation of the 8-Hour Primary and 
       Secondary National Ambient Air Quality Standards for Ozone

    1. General.
    This appendix explains the data handling conventions and 
computations necessary for determining whether the national 8-hour 
primary and secondary ambient air quality standards for ozone specified 
in Sec. 50.10 are met at an ambient ozone air quality monitoring site. 
Ozone is measured in the ambient air by a reference method based on 
appendix D of this part. Data reporting, data handling, and computation 
procedures to be used in making comparisons between reported ozone 
concentrations and the level of the ozone standard are specified in the 
following sections. Whether to exclude, retain, or make adjustments to 
the data affected by stratospheric ozone intrusion or other natural 
events is subject to the approval of the appropriate Regional 
Administrator.
    2. Primary and Secondary Ambient Air Quality Standards for Ozone.
    2.1  Data Reporting and Handling Conventions.
    2.1.1 Computing 8-hour averages. Hourly average concentrations shall 
be reported in parts per million (ppm) to the third decimal place, with 
additional digits to the right being truncated. Running 8-hour averages 
shall be computed from the hourly ozone concentration data for each hour 
of the year and the result shall be stored in the first, or start, hour 
of the 8-hour period. An 8-hour average shall be considered valid if at 
least 75% of the hourly averages for the 8-hour period are available. In 
the event that only 6 (or 7) hourly averages are available, the 8-hour 
average shall be computed on the basis of the hours available using 6 
(or 7) as the divisor. (8-hour periods with three or more missing hours 
shall not be ignored if, after substituting one-half the minimum 
detectable limit for the missing hourly concentrations, the 8-hour 
average concentration is greater than the level of the standard.) The 
computed 8-hour average ozone concentrations shall be reported to three 
decimal places (the insignificant digits to the right of the third 
decimal place are truncated, consistent with the data handling 
procedures for the reported data.)
    2.1.2  Daily maximum 8-hour average concentrations. (a) There are 24 
possible running 8-hour average ozone concentrations for each calendar 
day during the ozone monitoring season. (Ozone monitoring seasons vary 
by geographic location as designated in part 58, appendix D to this 
chapter.) The daily maximum 8-hour concentration for a given calendar 
day is the highest of the 24 possible 8-hour average concentrations 
computed for that day. This process is repeated, yielding a daily 
maximum 8-hour average ozone concentration for each calendar day with 
ambient ozone monitoring data. Because the 8-hour averages are recorded 
in the start hour, the daily maximum 8-hour concentrations from two 
consecutive days may have some hourly concentrations in common. 
Generally, overlapping daily maximum 8-hour averages are not likely, 
except in those non-urban monitoring locations with less pronounced 
diurnal variation in hourly concentrations.
    (b) An ozone monitoring day shall be counted as a valid day if valid 
8-hour averages are available for at least 75% of possible hours in the 
day (i.e., at least 18 of the 24 averages). In the event that less than 
75% of the 8-hour averages are available, a day shall also be counted as 
a valid day if the daily maximum 8-hour average concentration for that 
day is greater than the level of the ambient standard.
    2.2  Primary and Secondary Standard-related Summary Statistic. The 
standard-related summary statistic is the annual fourth-highest daily 
maximum 8-hour ozone concentration, expressed in parts per million, 
averaged over three years. The 3-year average shall be computed using 
the three most recent, consecutive calendar years of monitoring data 
meeting the data completeness requirements described in this appendix. 
The computed 3-year average of the annual fourth-highest daily maximum 
8-hour average ozone concentrations shall be expressed to three decimal 
places (the remaining digits to the right are truncated.)
    2.3 Comparisons with the Primary and Secondary Ozone Standards. (a) 
The primary and secondary ozone ambient air quality standards are met at 
an ambient air quality monitoring site when the 3-year average of the 
annual fourth-highest daily maximum 8-hour

[[Page 64]]

average ozone concentration is less than or equal to 0.08 ppm. The 
number of significant figures in the level of the standard dictates the 
rounding convention for comparing the computed 3-year average annual 
fourth-highest daily maximum 8-hour average ozone concentration with the 
level of the standard. The third decimal place of the computed value is 
rounded, with values equal to or greater than 5 rounding up. Thus, a 
computed 3-year average ozone concentration of 0.085 ppm is the smallest 
value that is greater than 0.08 ppm.
    (b) This comparison shall be based on three consecutive, complete 
calendar years of air quality monitoring data. This requirement is met 
for the three year period at a monitoring site if daily maximum 8-hour 
average concentrations are available for at least 90%, on average, of 
the days during the designated ozone monitoring season, with a minimum 
data completeness in any one year of at least 75% of the designated 
sampling days. When computing whether the minimum data completeness 
requirements have been met, meteorological or ambient data may be 
sufficient to demonstrate that meteorological conditions on missing days 
were not conducive to concentrations above the level of the standard. 
Missing days assumed less than the level of the standard are counted for 
the purpose of meeting the data completeness requirement, subject to the 
approval of the appropriate Regional Administrator.
    (c) Years with concentrations greater than the level of the standard 
shall not be ignored on the ground that they have less than complete 
data. Thus, in computing the 3-year average fourth maximum 
concentration, calendar years with less than 75% data completeness shall 
be included in the computation if the average annual fourth maximum 8-
hour concentration is greater than the level of the standard.
    (d) Comparisons with the primary and secondary ozone standards are 
demonstrated by examples 1 and 2 in paragraphs (d)(1) and (d) (2) 
respectively as follows:
    (1) As shown in example 1, the primary and secondary standards are 
met at this monitoring site because the 3-year average of the annual 
fourth-highest daily maximum 8-hour average ozone concentrations (i.e., 
0.084 ppm) is less than or equal to 0.08 ppm. The data completeness 
requirement is also met because the average percent of days with valid 
ambient monitoring data is greater than 90%, and no single year has less 
than 75% data completeness.

             Example 1. Ambient monitoring site attaining the primary and secondary ozone standards
----------------------------------------------------------------------------------------------------------------
                                                 1st Highest  2nd Highest  3rd Highest  4th Highest  5th Highest
                                      Percent    Daily Max 8- Daily Max 8- Daily Max 8- Daily Max 8- Daily Max 8-
               Year                  Valid Days   hour Conc.   hour Conc.   hour Conc.   hour Conc.   hour Conc.
                                                    (ppm)        (ppm)        (ppm)        (ppm)        (ppm)
----------------------------------------------------------------------------------------------------------------
1993..............................         100%        0.092        0.091        0.090        0.088        0.085
----------------------------------------------------------------------------------------------------------------
1994..............................          96%        0.090        0.089        0.086        0.084        0.080
----------------------------------------------------------------------------------------------------------------
1995..............................          98%        0.087        0.085        0.083        0.080        0.075
================================================================================================================
    Average.......................          98%
----------------------------------------------------------------------------------------------------------------

    (2) As shown in example 2, the primary and secondary standards are 
not met at this monitoring site because the 3-year average of the 
fourth-highest daily maximum 8-hour average ozone concentrations (i.e., 
0.093 ppm) is greater than 0.08 ppm. Note that the ozone concentration 
data for 1994 is used in these computations, even though the data 
capture is less than 75%, because the average fourth-highest daily 
maximum 8-hour average concentration is greater than 0.08 ppm.

          Example 2. Ambient Monitoring Site Failing to Meet the Primary and Secondary Ozone Standards
----------------------------------------------------------------------------------------------------------------
                                                 1st Highest  2nd Highest  3rd Highest  4th Highest  5th Highest
                                      Percent    Daily Max 8- Daily Max 8- Daily Max 8- Daily Max 8- Daily Max 8-
               Year                  Valid Days   hour Conc.   hour Conc.   hour Conc.   hour Conc.   hour Conc.
                                                    (ppm)        (ppm)        (ppm)        (ppm)        (ppm)
----------------------------------------------------------------------------------------------------------------
1993..............................          96%        0.105        0.103        0.103        0.102        0.102
----------------------------------------------------------------------------------------------------------------
1994..............................          74%        0.090        0.085        0.082        0.080        0.078
----------------------------------------------------------------------------------------------------------------
1995..............................          98%        0.103        0.101        0.101        0.097        0.095
================================================================================================================
    Average.......................          89%
----------------------------------------------------------------------------------------------------------------

[[Page 65]]

    3. Design Values for Primary and Secondary Ambient Air Quality 
Standards for Ozone. The air quality design value at a monitoring site 
is defined as that concentration that when reduced to the level of the 
standard ensures that the site meets the standard. For a concentration-
based standard, the air quality design value is simply the standard-
related test statistic. Thus, for the primary and secondary ozone 
standards, the 3-year average annual fourth-highest daily maximum 8-hour 
average ozone concentration is also the air quality design value for the 
site.

[62 FR 38895, July 18, 1997]

    Appendix J to Part 50--Reference Method for the Determination of 
         Particulate Matter as PM<INF>10</INF> in the Atmosphere

    1.0 Applicability.
    1.1 This method provides for the measurement of the mass 
concentration of particulate matter with an aerodynamic diameter less 
than or equal to a nominal 10 micrometers (PM<INF>1O</INF>) in ambient 
air over a 24-hour period for purposes of determining attainment and 
maintenance of the primary and secondary national ambient air quality 
standards for particulate matter specified in Sec. 50.6 of this chapter. 
The measurement process is nondestructive, and the PM<INF>10</INF> 
sample can be subjected to subsequent physical or chemical analyses. 
Quality assurance procedures and guidance are provided in part 58, 
appendices A and B, of this chapter and in References 1 and 2.
    2.0 Principle.
    2.1 An air sampler draws ambient air at a constant flow rate into a 
specially shaped inlet where the suspended particulate matter is 
inertially separated into one or more size fractions within the 
PM<INF>10</INF> size range. Each size fraction in the PM<INF>1O</INF> 
size range is then collected on a separate filter over the specified 
sampling period. The particle size discrimination characteristics 
(sampling effectiveness and 50 percent cutpoint) of the sampler inlet 
are prescribed as performance specifications in part 53 of this chapter.
    2.2 Each filter is weighed (after moisture equilibration) before and 
after use to determine the net weight (mass) gain due to collected 
PM<INF>10.</INF> The total volume of air sampled, corrected to EPA 
reference conditions (25 C, 101.3 kPa), is determined from the measured 
flow rate and the sampling time. The mass concentration of 
PM<INF>10</INF> in the ambient air is computed as the total mass of 
collected particles in the PM<INF>10</INF> size range divided by the 
volume of air sampled, and is expressed in micrograms per standard cubic 
meter (<greek mu<ls-thn-eq>g/std m\3\). For PM<INF>10</INF> samples 
collected at temperatures and pressures significantly different from EPA 
reference conditions, these corrected concentrations sometimes differ 
substantially from actual concentrations (in micrograms per actual cubic 
meter), particularly at high elevations. Although not required, the 
actual PM<INF>10</INF> concentration can be calculated from the 
corrected concentration, using the average ambient temperature and 
barometric pressure during the sampling period.
    2.3 A method based on this principle will be considered a reference 
method only if (a) the associated sampler meets the requirements 
specified in this appendix and the requirements in part 53 of this 
chapter, and (b) the method has been designated as a reference method in 
accordance with part 53 of this chapter.
    3.0 Range.
    3.1 The lower limit of the mass concentration range is determined by 
the repeatability of filter tare weights, assuming the nominal air 
sample volume for the sampler. For samplers having an automatic filter-
changing mechanism, there may be no upper limit. For samplers that do 
not have an automatic filter-changing mechanism, the upper limit is 
determined by the filter mass loading beyond which the sampler no longer 
maintains the operating flow rate within specified limits due to 
increased pressure drop across the loaded filter. This upper limit 
cannot be specified precisely because it is a complex function of the 
ambient particle size distribution and type, humidity, filter type, and 
perhaps other factors. Nevertheless, all samplers should be capable of 
measuring 24-hour PM<INF>10</INF> mass concentrations of at least 300 
<greek mu<ls-thn-eq>g/std m\3\ while maintaining the operating flow rate 
within the specified limits.
    4.0 Precision.
    4.1 The precision of PM<INF>10</INF> samplers must be 5 <greek 
mu<ls-thn-eq>g/m\3\ for PM<INF>10</INF> concentrations below 80 <greek 
mu<ls-thn-eq>g/m\3\ and 7 percent for PM<INF>10</INF> concentrations 
above 80 <greek mu<ls-thn-eq>g/m\3\, as required by part 53 of this 
chapter, which prescribes a test procedure that determines the variation 
in the PM<INF>10</INF> concentration measurements of identical samplers 
under typical sampling conditions. Continual assessment of precision via 
collocated samplers is required by part 58 of this chapter for 
PM<INF>10</INF> samplers used in certain monitoring networks.
    5.0 Accuracy.
    5.1 Because the size of the particles making up ambient particulate 
matter varies over a wide range and the concentration of particles 
varies with particle size, it is difficult to define the absolute 
accuracy of PM<INF>10</INF> samplers. Part 53 of this chapter provides a 
specification for the sampling effectiveness of PM<INF>10</INF> 
samplers. This specification requires that the expected mass 
concentration calculated for a candidate PM<INF>10</INF> sampler, when 
sampling a specified particle size distribution, be within +\10 percent 
of that calculated for an ideal sampler whose sampling effectiveness is 
explicitly specified. Also, the particle size for 50 percent sampling

[[Page 66]]

effectivensss is required to be 10+\0.5 micrometers. Other 
specifications related to accuracy apply to flow measurement and 
calibration, filter media, analytical (weighing) procedures, and 
artifact. The flow rate accuracy of PM<INF>10</INF> samplers used in 
certain monitoring networks is required by part 58 of this chapter to be 
assessed periodically via flow rate audits.
    6.0 Potential Sources of Error.
    6.1 Volatile Particles. Volatile particles collected on filters are 
often lost during shipment and/or storage of the filters prior to the 
post-sampling weighing \3\. Although shipment or storage of loaded 
filters is sometimes unavoidable, filters should be reweighed as soon as 
practical to minimize these losses.
    6.2 Artifacts. Positive errors in PM<INF>10</INF> concentration 
measurements may result from retention of gaseous species on filters 
<SUP>4, 5.</SUP> Such errors include the retention of sulfur dioxide and 
nitric acid. Retention of sulfur dioxide on filters, followed by 
oxidation to sulfate, is referred to as artifact sulfate formation, a 
phenomenon which increases with increasing filter alkalinity \6\. Little 
or no artifact sulfate formation should occur using filters that meet 
the alkalinity specification in section 7.2.4. Artifact nitrate 
formation, resulting primarily from retention of nitric acid, occurs to 
varying degrees on many filter types, including glass fiber, cellulose 
ester, and many quartz fiber filters <SUP>5, 7, 8, 9, 10.</SUP> Loss of 
true atmospheric particulate nitrate during or following sampling may 
also occur due to dissociation or chemical reaction. This phenomenon has 
been observed on Teflon<SUP><register mark<ls-thn-eq></SUP> filters \8\ 
and inferred for quartz fiber filters <SUP>11, 12.</SUP> The magnitude 
of nitrate artifact errors in PM<INF>10</INF> mass concentration 
measurements will vary with location and ambient temperature; however, 
for most sampling locations, these errors are expected to be small.
    6.3 Humidity. The effects of ambient humidity on the sample are 
unavoidable. The filter equilibration procedure in section 9.0 is 
designed to minimize the effects of moisture on the filter medium.
    6.4 Filter Handling. Careful handling of filters between presampling 
and postsampling weighings is necessary to avoid errors due to damaged 
filters or loss of collected particles from the filters. Use of a filter 
cartridge or cassette may reduce the magnitude of these errors. Filters 
must also meet the integrity specification in section 7.2.3.
    6.5 Flow Rate Variation. Variations in the sampler's operating flow 
rate may alter the particle size discrimination characteristics of the 
sampler inlet. The magnitude of this error will depend on the 
sensitivity of the inlet to variations in flow rate and on the particle 
distribution in the atmosphere during the sampling period. The use of a 
flow control device (section 7.1.3) is required to minimize this error.
    6.6 Air Volume Determination. Errors in the air volume determination 
may result from errors in the flow rate and/or sampling time 
measurements. The flow control device serves to minimize errors in the 
flow rate determination, and an elapsed time meter (section 7.1.5) is 
required to minimize the error in the sampling time measurement.
    7.0 Apparatus.
    7.1 PM<INF>10</INF> Sampler.
    7.1.1 The sampler shall be designed to:
    a. Draw the air sample into the sampler inlet and through the 
particle collection filter at a uniform face velocity.
    b. Hold and seal the filter in a horizontal position so that sample 
air is drawn downward through the filter.
    c. Allow the filter to be installed and removed conveniently.
    d. Protect the filter and sampler from precipitation and prevent 
insects and other debris from being sampled.
    e. Minimize air leaks that would cause error in the measurement of 
the air volume passing through the filter.
    f. Discharge exhaust air at a sufficient distance from the sampler 
inlet to minimize the sampling of exhaust air.
    g. Minimize the collection of dust from the supporting surface.
    7.1.2 The sampler shall have a sample air inlet system that, when 
operated within a specified flow rate range, provides particle size 
discrimination characteristics meeting all of the applicable performance 
specifications prescribed in part 53 of this chapter. The sampler inlet 
shall show no significant wind direction dependence. The latter 
requirement can generally be satisfied by an inlet shape that is 
circularly symmetrical about a vertical axis.
    7.1.3 The sampler shall have a flow control device capable of 
maintaining the sampler's operating flow rate within the flow rate 
limits specified for the sampler inlet over normal variations in line 
voltage and filter pressure drop.
    7.1.4 The sampler shall provide a means to measure the total flow 
rate during the sampling period. A continuous flow recorder is 
recommended but not required. The flow measurement device shall be 
accurate to +\2 percent.
    7.1.5 A timing/control device capable of starting and stopping the 
sampler shall be used to obtain a sample collection period of 24 +\1 hr 
(1,440 +\60 min). An elapsed time meter, accurate to within +\15 
minutes, shall be used to measure sampling time. This meter is optional 
for samplers with continuous flow recorders if the sampling time 
measurement obtained by means of the recorder meets the +\15 minute 
accuracy specification.

[[Page 67]]

    7.1.6 The sampler shall have an associated operation or instruction 
manual as required by part 53 of this chapter which includes detailed 
instructions on the calibration, operation, and maintenance of the 
sampler.
    7.2 Filters.
    7.2.1 Filter Medium. No commercially available filter medium is 
ideal in all respects for all samplers. The user's goals in sampling 
determine the relative importance of various filter characteristics 
(e.g., cost, ease of handling, physical and chemical characteristics, 
etc.) and, consequently, determine the choice among acceptable filters. 
Furthermore, certain types of filters may not be suitable for use with 
some samplers, particularly under heavy loading conditions (high mass 
concentrations), because of high or rapid increase in the filter flow 
resistance that would exceed the capability of the sampler's flow 
control device. However, samplers equipped with automatic filter-
changing mechanisms may allow use of these types of filters. The 
specifications given below are minimum requirements to ensure 
acceptability of the filter medium for measurement of PM<INF>10</INF> 
mass concentrations. Other filter evaluation criteria should be 
considered to meet individual sampling and analysis objectives.
    7.2.2 Collection Efficiency. </=99 percent, as measured by the DOP 
test (ASTM-2986) with 0.3 <greek mu<ls-thn-eq>m particles at the 
sampler's operating face velocity.
    7.2.3 Integrity. +\5 <greek mu<ls-thn-eq>g/m\3\ (assuming sampler's 
nominal 24-hour air sample volume). Integrity is measured as the 
PM<INF>10</INF> concentration equivalent corresponding to the average 
difference between the initial and the final weights of a random sample 
of test filters that are weighed and handled under actual or simulated 
sampling conditions, but have no air sample passed through them (i.e., 
filter blanks). As a minimum, the test procedure must include initial 
equilibration and weighing, installation on an inoperative sampler, 
removal from the sampler, and final equilibration and weighing.
    7.2.4 Alkalinity. <25 microequivalents/gram of filter, as measured 
by the procedure given in Reference 13 following at least two months 
storage in a clean environment (free from contamination by acidic gases) 
at room temperature and humidity.
    7.3 Flow Rate Transfer Standard. The flow rate transfer standard 
must be suitable for the sampler's operating flow rate and must be 
calibrated against a primary flow or volume standard that is traceable 
to the National Bureau of Standards (NBS). The flow rate transfer 
standard must be capable of measuring the sampler's operating flow rate 
with an accuracy of +\2 percent.
    7.4 Filter Conditioning Environment.
    7.4.1 Temperature range: 15 to 30 C.
    7.4.2 Temperature control: +\3 C.
    7.4.3 Humidity range: 20% to 45% RH.
    7.4.4 Humidity control: +\5% RH.
    7.5 Analytical Balance. The analytical balance must be suitable for 
weighing the type and size of filters required by the sampler. The range 
and sensitivity required will depend on the filter tare weights and mass 
loadings. Typically, an analytical balance with a sensitivity of 0.1 mg 
is required for high volume samplers (flow rates <ls-thn-eq>0.5 m\3\/
min). Lower volume samplers (flow rates <0.5 m\3\/min) will require a 
more sensitive balance.
    8.0 Calibration.
    8.1 General Requirements.
    8.1.1 Calibration of the sampler's flow measurement device is 
required to establish traceability of subsequent flow measurements to a 
primary standard. A flow rate transfer standard calibrated against a 
primary flow or volume standard shall be used to calibrate or verify the 
accuracy of the sampler's flow measurement device.
    8.1.2 Particle size discrimination by inertial separation requires 
that specific air velocities be maintained in the sampler's air inlet 
system. Therefore, the flow rate through the sampler's inlet must be 
maintained throughout the sampling period within the design flow rate 
range specified by the manufacturer. Design flow rates are specified as 
actual volumetric flow rates, measured at existing conditions of 
temperature and pressure (Q<INF>a</INF>). In contrast, mass 
concentrations of PM<INF>10</INF> are computed using flow rates 
corrected to EPA reference conditions of temperature and pressure 
(Q<INF>std</INF>).
    8.2 Flow Rate Calibration Procedure.
    8.2.1 PM<INF>10</INF> samplers employ various types of flow control 
and flow measurement devices. The specific procedure used for flow rate 
calibration or verification will vary depending on the type of flow 
controller and flow indicator employed. Calibration in terms of actual 
volumetric flow rates (Q<INF>a</INF>) is generally recommended, but 
other measures of flow rate (e.g., Q<INF>std</INF>) may be used provided 
the requirements of section 8.1 are met. The general procedure given 
here is based on actual volumetric flow units (Q<INF>a</INF>) and serves 
to illustrate the steps involved in the calibration of a PM<INF>10</INF> 
sampler. Consult the sampler manufacturer's instruction manual and 
Reference 2 for specific guidance on calibration. Reference 14 provides 
additional information on the use of the commonly used measures of flow 
rate and their interrelationships.
    8.2.2 Calibrate the flow rate transfer standard against a primary 
flow or volume standard traceable to NBS. Establish a calibration 
relationship (e.g., an equation or family of curves) such that 
traceability to the primary standard is accurate to within 2 percent 
over the expected range of ambient conditions (i.e., temperatures and 
pressures) under which the transfer standard will be used. Recalibrate 
the transfer standard periodically.

[[Page 68]]

    8.2.3 Following the sampler manufacturer's instruction manual, 
remove the sampler inlet and connect the flow rate transfer standard to 
the sampler such that the transfer standard accurately measures the 
sampler's flow rate. Make sure there are no leaks between the transfer 
standard and the sampler.
    8.2.4 Choose a minimum of three flow rates (actual m\3\/min), spaced 
over the acceptable flow rate range specified for the inlet (see 7.1.2) 
that can be obtained by suitable adjustment of the sampler flow rate. In 
accordance with the sampler manufacturer's instruction manual, obtain or 
verify the calibration relationship between the flow rate (actual m\3\/
min) as indicated by the transfer standard and the sampler's flow 
indicator response. Record the ambient temperature and barometric 
pressure. Temperature and pressure corrections to subsequent flow 
indicator readings may be required for certain types of flow measurement 
devices. When such corrections are necessary, correction on an 
individual or daily basis is preferable. However, seasonal average 
temperature and average barometric pressure for the sampling site may be 
incorporated into the sampler calibration to avoid daily corrections. 
Consult the sampler manufacturer's instruction manual and Reference 2 
for additional guidance.
    8.2.5 Following calibration, verify that the sampler is operating at 
its design flow rate (actual m\3\/min) with a clean filter in place.
    8.2.6 Replace the sampler inlet.
    9.0 Procedure.
    9.1 The sampler shall be operated in accordance with the specific 
guidance provided in the sampler manufacturer's instruction manual and 
in Reference 2. The general procedure given here assumes that the 
sampler's flow rate calibration is based on flow rates at ambient 
conditions (Q<INF>a</INF>) and serves to illustrate the steps involved 
in the operation of a PM<INF>10</INF> sampler.
    9.2 Inspect each filter for pinholes, particles, and other 
imperfections. Establish a filter information record and assign an 
identification number to each filter.
    9.3 Equilibrate each filter in the conditioning environment (see 
7.4) for at least 24 hours.
    9.4 Following equilibration, weigh each filter and record the 
presampling weight with the filter identification number.
    9.5 Install a preweighed filter in the sampler following the 
instructions provided in the sampler manufacturer's instruction manual.
    9.6 Turn on the sampler and allow it to establish run-temperature 
conditions. Record the flow indicator reading and, if needed, the 
ambient temperature and barometric pressure. Determine the sampler flow 
rate (actual m\3\/min) in accordance with the instructions provided in 
the sampler manufacturer's instruction manual. NOTE.--No onsite 
temperature or pressure measurements are necessary if the sampler's flow 
indicator does not require temperature or pressure corrections or if 
seasonal average temperature and average barometric pressure for the 
sampling site are incorporated into the sampler calibration (see step 
8.2.4). If individual or daily temperature and pressure corrections are 
required, ambient temperature and barometric pressure can be obtained by 
on-site measurements or from a nearby weather station. Barometric 
pressure readings obtained from airports must be station pressure, not 
corrected to sea level, and may need to be corrected for differences in 
elevation between the sampling site and the airport.
    9.7 If the flow rate is outside the acceptable range specified by 
the manufacturer, check for leaks, and if necessary, adjust the flow 
rate to the specified setpoint. Stop the sampler.
    9.8 Set the timer to start and stop the sampler at appropriate 
times. Set the elapsed time meter to zero or record the initial meter 
reading.
    9.9 Record the sample information (site location or identification 
number, sample date, filter identification number, and sampler model and 
serial number).
    9.10 Sample for 24+\1 hours.
    9.11 Determine and record the average flow rate (Q<INF>a</INF>) in 
actual m\3\/min for the sampling period in accordance with the 
instructions provided in the sampler manufacturer's instruction manual. 
Record the elapsed time meter final reading and, if needed, the average 
ambient temperature and barometric pressure for the sampling period (see 
note following step 9.6).
    9.12 Carefully remove the filter from the sampler, following the 
sampler manufacturer's instruction manual. Touch only the outer edges of 
the filter.
    9.13 Place the filter in a protective holder or container (e.g., 
petri dish, glassine envelope, or manila folder).
    9.14 Record any factors such as meteorological conditions, 
construction activity, fires or dust storms, etc., that might be 
pertinent to the measurement on the filter information record.
    9.15 Transport the exposed sample filter to the filter conditioning 
environment as soon as possible for equilibration and subsequent 
weighing.
    9.16 Equilibrate the exposed filter in the conditioning environment 
for at least 24 hours under the same temperature and humidity conditions 
used for presampling filter equilibration (see 9.3).
    9.17 Immediately after equilibration, reweigh the filter and record 
the postsampling weight with the filter identification number.
    10.0 Sampler Maintenance.
    10.1 The PM<INF>10</INF> sampler shall be maintained in strict 
accordance with the maintenance

[[Page 69]]

procedures specified in the sampler manufacturer's instruction manual.
    11.0 Calculations.
    11.1 Calculate the average flow rate over the sampling period 
corrected to EPA reference conditions as Q<INF>std.</INF> When the 
sampler's flow indicator is calibrated in actual volumetric units 
(Q<INF>a</INF>), Q<INF>std</INF> is calculated as:

Q<INF>std</INF>=Q<INF>a</INF>x(P<INF>av</INF>/
T<INF>av</INF>)(T<INF>std</INF>/P<INF>std</INF>)

where

Q<INF>std</INF> = average flow rate at EPA reference conditions, std 
m\3\/min;
Q<INF>a</INF> = average flow rate at ambient conditions, m\3\/min;
P<INF>av</INF> = average barometric pressure during the sampling period 
or average barometric pressure for the sampling site, kPa (or mm Hg);
T<INF>av</INF> = average ambient temperature during the sampling period 
or seasonal average ambient temperature for the sampling site, K;
T<INF>std</INF> = standard temperature, defined as 298 K;
P<INF>std</INF> = standard pressure, defined as 101.3 kPa (or 760 mm 
Hg).

    11.2 Calculate the total volume of air sampled as:

V<INF>std</INF> = Q<INF>std</INF>xt

where

V<INF>std</INF> = total air sampled in standard volume units, std m\3\;
t = sampling time, min.

    11.3 Calculate the PM<INF>10</INF> concentration as:

PM<INF>10</INF> = (W<INF>f</INF>-W<INF>i</INF>)x10\6\/V<INF>std</INF>

where

PM<INF>10</INF> = mass concentration of PM<INF>10,</INF> <greek 
mu<ls-thn-eq>g/std m\3\;
W<INF>f,</INF> W<INF>i</INF> = final and initial weights of filter 
collecting PM<INF>1O</INF> particles, g;
10\6\ = conversion of g to <greek mu<ls-thn-eq>g.

    Note: If more than one size fraction in the PM<INF>10</INF> size 
range is collected by the sampler, the sum of the net weight gain by 
each collection filter [<greek sigma<ls-thn-eq>(W<INF>f</INF>-
W<INF>i</INF>)] is used to calculate the PM<INF>10</INF> mass 
concentration.
    12.0 References.
    1. Quality Assurance Handbook for Air Pollution Measurement Systems, 
Volume I, Principles. EPA-600/9-76-005, March 1976. Available from CERI, 
ORD Publications, U.S. Environmental Protection Agency, 26 West St. 
Clair Street, Cincinnati, OH 45268.
    2. Quality Assurance Handbook for Air Pollution Measurement Systems, 
Volume II, Ambient Air Specific Methods. EPA-600/4-77-027a, May 1977. 
Available from CERI, ORD Publications, U.S. Environmental Protection 
Agency, 26 West St. Clair Street, Cincinnati, OH 45268.
    3. Clement, R.E., and F.W. Karasek. Sample Composition Changes in 
Sampling and Analysis of Organic Compounds in Aerosols. Int. J. Environ. 
Analyt. Chem., 7:109, 1979.
    4. Lee, R.E., Jr., and J. Wagman. A Sampling Anomaly in the 
Determination of Atmospheric Sulfate Concentration. Amer. Ind. Hyg. 
Assoc. J., 27:266, 1966.
    5. Appel, B.R., S.M. Wall, Y. Tokiwa, and M. Haik. Interference 
Effects in Sampling Particulate Nitrate in Ambient Air. Atmos. Environ., 
13:319, 1979.
    6. Coutant, R.W. Effect of Environmental Variables on Collection of 
Atmospheric Sulfate. Environ. Sci. Technol., 11:873, 1977.
    7. Spicer, C.W., and P. Schumacher. Interference in Sampling 
Atmospheric Particulate Nitrate. Atmos. Environ., 11:873, 1977.
    8. Appel, B.R., Y. Tokiwa, and M. Haik. Sampling of Nitrates in 
Ambient Air. Atmos. Environ., 15:283, 1981.
    9. Spicer, C.W., and P.M. Schumacher. Particulate Nitrate: 
Laboratory and Field Studies of Major Sampling Interferences. Atmos. 
Environ., 13:543, 1979.
    10. Appel, B.R. Letter to Larry Purdue, U.S. EPA, Environmental 
Monitoring and Support Laboratory. March 18, 1982, Docket No. A-82-37, 
II-I-1.
    11. Pierson, W.R., W.W. Brachaczek, T.J. Korniski, T.J. Truex, and 
J.W. Butler. Artifact Formation of Sulfate, Nitrate, and Hydrogen Ion on 
Backup Filters: Allegheny Mountain Experiment. J. Air Pollut. Control 
Assoc., 30:30, 1980.
    12. Dunwoody, C.L. Rapid Nitrate Loss From PM<INF>10</INF> Filters. 
J. Air Pollut. Control Assoc., 36:817, 1986.
    13. Harrell, R.M. Measuring the Alkalinity of Hi-Vol Air Filters. 
EMSL/RTP-SOP-QAD-534, October 1985. Available from the U.S. 
Environmental Protection Agency, EMSL/QAD, Research Triangle Park, NC 
27711.
    14. Smith, F., P.S. Wohlschlegel, R.S.C. Rogers, and D.J. Mulligan. 
Investigation of Flow Rate Calibration Procedures Associated With the 
High Volume Method for Determination of Suspended Particulates. EPA-600/
4-78-047, U.S. Environmental Protection Agency, Research Triangle Park, 
NC 27711, 1978.

[52 FR 24664, July 1, 1987; 52 FR 29467, Aug. 7, 1987]

   Appendix K to Part 50--Interpretation of the National Ambient Air 
                Quality Standards for Particulate Matter

    1.0  General.
    (a) This appendix explains the computations necessary for analyzing 
particulate matter data to determine attainment of the 24-hour and 
annual standards specified in 40 CFR 50.6. For the primary and secondary 
standards, particulate matter is measured in the ambient air as 
PM<INF>10</INF> (particles with an aerodynamic diameter less than or 
equal to

[[Page 70]]

a nominal 10 micrometers) by a reference method based on appendix J of 
this part and designated in accordance with part 53 of this chapter, or 
by an equivalent method designated in accordance with part 53 of this 
chapter. The required frequency of measurements is specified in part 58 
of this chapter.
    (b) The terms used in this appendix are defined as follows:
    Average refers to an arithmetic mean. All particulate matter 
standards are expressed in terms of expected annual values: Expected 
number of exceedances per year for the 24-hour standards and expected 
annual arithmetic mean for the annual standards.
    Daily value for PM<INF>10</INF> refers to the 24-hour average 
concentration of PM<INF>10</INF> calculated or measured from midnight to 
midnight (local time).
    Exceedance means a daily value that is above the level of the 24-
hour standard after rounding to the nearest 10 <greek mu<ls-thn-eq>g/
m\3\ (i.e., values ending in 5 or greater are to be rounded up).
    Expected annual value is the number approached when the annual 
values from an increasing number of years are averaged, in the absence 
of long-term trends in emissions or meteorological conditions.
    Year refers to a calendar year.
    (c) Although the discussion in this appendix focuses on monitored 
data, the same principles apply to modeling data, subject to EPA 
modeling guidelines.
    2.0  Attainment Determinations.
    2.1  24-Hour Primary and Secondary Standards.
    (a) Under 40 CFR 50.6(a) the 24-hour primary and secondary standards 
are attained when the expected number of exceedances per year at each 
monitoring site is less than or equal to one. In the simplest case, the 
number of expected exceedances at a site is determined by recording the 
number of exceedances in each calendar year and then averaging them over 
the past 3 calendar years. Situations in which 3 years of data are not 
available and possible adjustments for unusual events or trends are 
discussed in sections 2.3 and 2.4 of this appendix. Further, when data 
for a year are incomplete, it is necessary to compute an estimated 
number of exceedances for that year by adjusting the observed number of 
exceedances. This procedure, performed by calendar quarter, is described 
in section 3.0 of this appendix. The expected number of exceedances is 
then estimated by averaging the individual annual estimates for the past 
3 years.
    (b) The comparison with the allowable expected exceedance rate of 
one per year is made in terms of a number rounded to the nearest tenth 
(fractional values equal to or greater than 0.05 are to be rounded up; 
e.g., an exceedance rate of 1.05 would be rounded to 1.1, which is the 
lowest rate for nonattainment).
    2.2  Annual Primary and Secondary Standards. Under 40 CFR 50.6(b), 
the annual primary and secondary standards are attained when the 
expected annual arithmetic mean PM<INF>10</INF> concentration is less 
than or equal to the level of the standard. In the simplest case, the 
expected annual arithmetic mean is determined by averaging the annual 
arithmetic mean PM<INF>10</INF> concentrations for the past 3 calendar 
years. Because of the potential for incomplete data and the possible 
seasonality in PM<INF>10</INF> concentrations, the annual mean shall be 
calculated by averaging the four quarterly means of PM<INF>10</INF> 
concentrations within the calendar year. The equations for calculating 
the annual arithmetic mean are given in section 4.0 of this appendix. 
Situations in which 3 years of data are not available and possible 
adjustments for unusual events or trends are discussed in sections 2.3 
and 2.4 of this appendix. The expected annual arithmetic mean is rounded 
to the nearest 1 <greek mu<ls-thn-eq>g/m\3\ before comparison with the 
annual standards (fractional values equal to or greater than 0.5 are to 
be rounded up).
    2.3  Data Requirements.
    (a) 40 CFR 58.13 specifies the required minimum frequency of 
sampling for PM<INF>10</INF>. For the purposes of making comparisons 
with the particulate matter standards, all data produced by National Air 
Monitoring Stations (NAMS), State and Local Air Monitoring Stations 
(SLAMS) and other sites submitted to EPA in accordance with the part 58 
requirements must be used, and a minimum of 75 percent of the scheduled 
PM<INF>10</INF> samples per quarter are required.
    (b) To demonstrate attainment of either the annual or 24-hour 
standards at a monitoring site, the monitor must provide sufficient data 
to perform the required calculations of sections 3.0 and 4.0 of this 
appendix. The amount of data required varies with the sampling 
frequency, data capture rate and the number of years of record. In all 
cases, 3 years of representative monitoring data that meet the 75 
percent criterion of the previous paragraph should be utilized, if 
available, and would suffice. More than 3 years may be considered, if 
all additional representative years of data meeting the 75 percent 
criterion are utilized. Data not meeting these criteria may also suffice 
to show attainment; however, such exceptions will have to be approved by 
the appropriate Regional Administrator in accordance with EPA guidance.
    (c) There are less stringent data requirements for showing that a 
monitor has failed an attainment test and thus has recorded a violation 
of the particulate matter standards. Although it is generally necessary 
to meet the minimum 75 percent data capture requirement per quarter to 
use the computational equations described in sections 3.0 and 4.0 of 
this appendix, this criterion does not

[[Page 71]]

apply when less data is sufficient to unambiguously establish 
nonattainment. The following examples illustrate how nonattainment can 
be demonstrated when a site fails to meet the completeness criteria. 
Nonattainment of the 24-hour primary standards can be established by the 
observed annual number of exceedances (e.g., four observed exceedances 
in a single year), or by the estimated number of exceedances derived 
from the observed number of exceedances and the required number of 
scheduled samples (e.g., two observed exceedances with every other day 
sampling). Nonattainment of the annual standards can be demonstrated on 
the basis of quarterly mean concentrations developed from observed data 
combined with one-half the minimum detectable concentration substituted 
for missing values. In both cases, expected annual values must exceed 
the levels allowed by the standards.
    2.4  Adjustment for Exceptional Events and Trends.
    (a) An exceptional event is an uncontrollable event caused by 
natural sources of particulate matter or an event that is not expected 
to recur at a given location. Inclusion of such a value in the 
computation of exceedances or averages could result in inappropriate 
estimates of their respective expected annual values. To reduce the 
effect of unusual events, more than 3 years of representative data may 
be used. Alternatively, other techniques, such as the use of statistical 
models or the use of historical data could be considered so that the 
event may be discounted or weighted according to the likelihood that it 
will recur. The use of such techniques is subject to the approval of the 
appropriate Regional Administrator in accordance with EPA guidance.
    (b) In cases where long-term trends in emissions and air quality are 
evident, mathematical techniques should be applied to account for the 
trends to ensure that the expected annual values are not inappropriately 
biased by unrepresentative data. In the simplest case, if 3 years of 
data are available under stable emission conditions, this data should be 
used. In the event of a trend or shift in emission patterns, either the 
most recent representative year(s) could be used or statistical 
techniques or models could be used in conjunction with previous years of 
data to adjust for trends. The use of less than 3 years of data, and any 
adjustments are subject to the approval of the appropriate Regional 
Administrator in accordance with EPA guidance.
    3.0  Computational Equations for the 24-hour Standards.
    3.1  Estimating Exceedances for a Year.
    (a) If PM<INF>10</INF> sampling is scheduled less frequently than 
every day, or if some scheduled samples are missed, a PM<INF>10</INF> 
value will not be available for each day of the year. To account for the 
possible effect of incomplete data, an adjustment must be made to the 
data collected at each monitoring location to estimate the number of 
exceedances in a calendar year. In this adjustment, the assumption is 
made that the fraction of missing values that would have exceeded the 
standard level is identical to the fraction of measured values above 
this level. This computation is to be made for all sites that are 
scheduled to monitor throughout the entire year and meet the minimum 
data requirements of section 2.3 of this appendix. Because of possible 
seasonal imbalance, this adjustment shall be applied on a quarterly 
basis. The estimate of the expected number of exceedances for the 
quarter is equal to the observed number of exceedances plus an increment 
associated with the missing data. The following equation must be used 
for these computations:

                               Equation 1
[GRAPHIC] [TIFF OMITTED] TR18JY97.180

where:

e<INF>q</INF> = the estimated number of exceedances for calendar quarter 
q;
v<INF>q</INF> = the observed number of exceedances for calendar quarter 
q;
N<INF>q</INF> = the number of days in calendar quarter q;
n<INF>q</INF> = the number of days in calendar quarter q with 
PM<INF>10</INF> data; and
q = the index for calendar quarter, q=1, 2, 3 or 4.

    (b) The estimated number of exceedances for a calendar quarter must 
be rounded to the nearest hundredth (fractional values equal to or 
greater than 0.005 must be rounded up).
    (c) The estimated number of exceedances for the year, e, is the sum 
of the estimates for each calendar quarter.

                               Equation 2
[GRAPHIC] [TIFF OMITTED] TR18JY97.181

    (d) The estimated number of exceedances for a single year must be 
rounded to one decimal place (fractional values equal to or greater than 
0.05 are to be rounded up). The expected number of exceedances is then 
estimated by averaging the individual annual estimates for the most 
recent 3 or more representative years of data. The expected number of 
exceedances must be rounded to one decimal place (fractional values 
equal to or greater than 0.05 are to be rounded up).

[[Page 72]]

    (e) The adjustment for incomplete data will not be necessary for 
monitoring or modeling data which constitutes a complete record, i.e., 
365 days per year.
    (f) To reduce the potential for overestimating the number of 
expected exceedances, the correction for missing data will not be 
required for a calendar quarter in which the first observed exceedance 
has occurred if:
    (1) There was only one exceedance in the calendar quarter;
    (2) Everyday sampling is subsequently initiated and maintained for 4 
calendar quarters in accordance with 40 CFR 58.13; and
    (3) Data capture of 75 percent is achieved during the required 
period of everyday sampling. In addition, if the first exceedance is 
observed in a calendar quarter in which the monitor is already sampling 
every day, no adjustment for missing data will be made to the first 
exceedance if a 75 percent data capture rate was achieved in the quarter 
in which it was observed.

                                Example 1

    a. During a particular calendar quarter, 39 out of a possible 92 
samples were recorded, with one observed exceedance of the 24-hour 
standard. Using Equation 1, the estimated number of exceedances for the 
quarter is:

e<INF>q</INF>=1x92/39=2.359 or 2.36.

    b. If the estimated exceedances for the other 3 calendar quarters in 
the year were 2.30, 0.0 and 0.0, then, using Equation 2, the estimated 
number of exceedances for the year is 2.36=2.30=0.0=0.0 which equals 
4.66 or 4.7. If no exceedances were observed for the 2 previous years, 
then the expected number of exceedances is estimated by: (1/
3)x(4.7=0=0)=1.57 or 1.6. Since 1.6 exceeds the allowable number of 
expected exceedances, this monitoring site would fail the attainment 
test.

                                Example 2

    In this example, everyday sampling was initiated following the first 
observed exceedance as required by 40 CFR 58.13. Accordingly, the first 
observed exceedance would not be adjusted for incomplete sampling. 
During the next three quarters, 1.2 exceedances were estimated. In this 
case, the estimated exceedances for the year would be 1.0=1.2=0.0=0.0 
which equals 2.2. If, as before, no exceedances were observed for the 
two previous years, then the estimated exceedances for the 3-year period 
would then be (1/3)x(2.2=0.0=0.0)=0.7, and the monitoring site would not 
fail the attainment test.
    3.2 Adjustments for Non-Scheduled Sampling Days.
    (a) If a systematic sampling schedule is used and sampling is 
performed on days in addition to the days specified by the systematic 
sampling schedule, e.g., during episodes of high pollution, then an 
adjustment must be made in the eqution for the estimation of 
exceedances. Such an adjustment is needed to eliminate the bias in the 
estimate of the quarterly and annual number of exceedances that would 
occur if the chance of an exceedance is different for scheduled than for 
non-scheduled days, as would be the case with episode sampling.
    (b) The required adjustment treats the systematic sampling schedule 
as a stratified sampling plan. If the period from one scheduled sample 
until the day preceding the next scheduled sample is defined as a 
sampling stratum, then there is one stratum for each scheduled sampling 
day. An average number of observed exceedances is computed for each of 
these sampling strata. With nonscheduled sampling days, the estimated 
number of exceedances is defined as:

                               Equation 3
[GRAPHIC] [TIFF OMITTED] TR18JY97.182

where:

e<INF>q</INF> = the estimated number of exceedances for the quarter;
N<INF>q</INF> = the number of days in the quarter;
m<INF>q</INF> = the number of strata with samples during the quarter;
v<INF>j</INF> = the number of observed exceedances in stratum j; and
k<INF>j</INF> = the number of actual samples in stratum j.

    (c) Note that if only one sample value is recorded in each stratum, 
then Equation 3 reduces to Equation 1.

                                Example 3

    A monitoring site samples according to a systematic sampling 
schedule of one sample every 6 days, for a total of 15 scheduled samples 
in a quarter out of a total of 92 possible samples. During one 6-day 
period, potential episode levels of PM<INF>10</INF> were suspected, so 5 
additional samples were taken. One of the regular scheduled samples was 
missed, so a total of 19 samples in 14 sampling strata were measured. 
The one 6-day sampling stratum with 6 samples recorded 2 exceedances. 
The remainder of the quarter with one sample per stratum recorded zero 
exceedances. Using Equation 3, the estimated number of exceedances for 
the quarter is:

e<INF>q</INF>=(92/14)x(2/6=0=. . .=0)=2.19.

    4.0 Computational Equations for Annual Standards.
    4.1 Calculation of the Annual Arithmetic Mean. (a) An annual 
arithmetic mean value for PM<INF>10</INF> is determined by averaging the 
quarterly means for the 4 calendar quarters of the year. The following 
equation is to be

[[Page 73]]

used for calculation of the mean for a calendar quarter:

                               Equation 4
[GRAPHIC] [TIFF OMITTED] TR18JY97.183

where:

x<INF>q</INF> = the quarterly mean concentration for quarter q, q=1, 2, 
3, or 4,
n<INF>q</INF> = the number of samples in the quarter, and
x<INF>i</INF> = the ith concentration value recorded in the quarter.

    (b) The quarterly mean, expressed in <greek mu<ls-thn-eq>g/m\3\, 
must be rounded to the nearest tenth (fractional values of 0.05 should 
be rounded up).
    (c) The annual mean is calculated by using the following equation:

                               Equation 5
[GRAPHIC] [TIFF OMITTED] TR18JY97.184

where:

x = the annual mean; and
x<INF>q</INF> = the mean for calendar quarter q.

    (d) The average of quarterly means must be rounded to the nearest 
tenth (fractional values of 0.05 should be rounded up).
    (e) The use of quarterly averages to compute the annual average will 
not be necessary for monitoring or modeling data which results in a 
complete record, i.e., 365 days per year.
    (f) The expected annual mean is estimated as the average of three or 
more annual means. This multi-year estimate, expressed in <greek 
mu<ls-thn-eq>g/m\3\, shall be rounded to the nearest integer for 
comparison with the annual standard (fractional values of 0.5 should be 
rounded up).

                                Example 4

    Using Equation 4, the quarterly means are calculated for each 
calendar quarter. If the quarterly means are 52.4, 75.3, 82.1, and 63.2 
<greek mu<ls-thn-eq>g/m \3\, then the annual mean is:

x = (1/4)x(52.4=75.3=82.1=63.2) = 68.25 or 68.3.

    4.2 Adjustments for Non-scheduled Sampling Days. (a) An adjustment 
in the calculation of the annual mean is needed if sampling is performed 
on days in addition to the days specified by the systematic sampling 
schedule. For the same reasons given in the discussion of estimated 
exceedances, under section 3.2 of this appendix, the quarterly averages 
would be calculated by using the following equation:

                               Equation 6
[GRAPHIC] [TIFF OMITTED] TR18JY97.185

where:

x<INF>q</INF> = the quarterly mean concentration for quarter q, q=1, 2, 
3, or 4;
x<INF>ij</INF> = the ith concentration value recorded in stratum j;
k<INF>j</INF> = the number of actual samples in stratum j; and
m<INF>q</INF> = the number of strata with data in the quarter.

    (b) If one sample value is recorded in each stratum, Equation 6 
reduces to a simple arithmetic average of the observed values as 
described by Equation 4.

                                Example 5

    a. During one calendar quarter, 9 observations were recorded. These 
samples were distributed among 7 sampling strata, with 3 observations in 
one stratum. The concentrations of the 3 observations in the single 
stratum were 202, 242, and 180 <greek mu<ls-thn-eq>g/m\3\. The remaining 
6 observed concentrations were 55, 68, 73, 92, 120, and 155 <greek 
mu<ls-thn-eq>g/m\3\. Applying the weighting factors specified in 
Equation 6, the quarterly mean is:

x<INF>q</INF> = (1/7) x [(1/3) x (202 = 242 = 180) = 155 = 68 = 73 = 92 
= 120 = 155] = 110.1

    b. Although 24-hour measurements are rounded to the nearest 10 
<greek mu<ls-thn-eq>g/m\3\ for determinations of exceedances of the 24-
hour standard, note that these values are rounded to the nearest 1 
<greek mu<ls-thn-eq>g/m\3\ for the calculation of means.

[62 FR 38712, July 18, 1997]

 Appendix L to Part 50--Reference Method for the Determination of Fine 
        Particulate Matter as PM<INF>2.5</INF> in the Atmosphere

    1.0 Applicability.
    1.1 This method provides for the measurement of the mass 
concentration of fine particulate matter having an aerodynamic diameter 
less than or equal to a nominal 2.5 micrometers (PM<INF>2.5</INF>) in 
ambient air over a 24-hour period for purposes of determining whether 
the primary and secondary national ambient air quality standards for 
fine particulate matter specified in Sec. 50.7 of this part are met. The 
measurement process is considered to be nondestructive, and the 
PM<INF>2.5</INF> sample obtained can be subjected to subsequent physical 
or chemical analyses. Quality assessment procedures are provided in part 
58, appendix A of this chapter, and quality assurance guidance are 
provided in references 1, 2, and 3 in section 13.0 of this appendix.

[[Page 74]]

    1.2 This method will be considered a reference method for purposes 
of part 58 of this chapter only if:
    (a) The associated sampler meets the requirements specified in this 
appendix and the applicable requirements in part 53 of this chapter, and
    (b) The method and associated sampler have been designated as a 
reference method in accordance with part 53 of this chapter.
    1.3 PM<INF>2.5</INF> samplers that meet nearly all specifications 
set forth in this method but have minor deviations and/or modifications 
of the reference method sampler will be designated as ``Class I'' 
equivalent methods for PM<INF>2.5</INF> in accordance with part 53 of 
this chapter.
    2.0 Principle.
    2.1 An electrically powered air sampler draws ambient air at a 
constant volumetric flow rate into a specially shaped inlet and through 
an inertial particle size separator (impactor) where the suspended 
particulate matter in the PM<INF>2.5</INF> size range is separated for 
collection on a polytetrafluoroethylene (PTFE) filter over the specified 
sampling period. The air sampler and other aspects of this reference 
method are specified either explicitly in this appendix or generally 
with reference to other applicable regulations or quality assurance 
guidance.
    2.2 Each filter is weighed (after moisture and temperature 
conditioning) before and after sample collection to determine the net 
gain due to collected PM<INF>2.5</INF>. The total volume of air sampled 
is determined by the sampler from the measured flow rate at actual 
ambient temperature and pressure and the sampling time. The mass 
concentration of PM<INF>2.5</INF> in the ambient air is computed as the 
total mass of collected particles in the PM<INF>2.5</INF> size range 
divided by the actual volume of air sampled, and is expressed in 
micrograms per cubic meter of air (<greek mu<ls-thn-eq>g/m\3\).
    3.0 PM<INF>2.5</INF> Measurement Range.
    3.1 Lower concentration limit. The lower detection limit of the mass 
concentration measurement range is estimated to be approximately 2 
<greek mu<ls-thn-eq>g/m\3\, based on noted mass changes in field blanks 
in conjunction with the 24 m\3\ nominal total air sample volume 
specified for the 24-hour sample.
    3.2 Upper concentration limit. The upper limit of the mass 
concentration range is determined by the filter mass loading beyond 
which the sampler can no longer maintain the operating flow rate within 
specified limits due to increased pressure drop across the loaded 
filter. This upper limit cannot be specified precisely because it is a 
complex function of the ambient particle size distribution and type, 
humidity, the individual filter used, the capacity of the sampler flow 
rate control system, and perhaps other factors. Nevertheless, all 
samplers are estimated to be capable of measuring 24-hour 
PM<INF>2.5</INF> mass concentrations of at least 200 <greek 
mu<ls-thn-eq>g/m\3\ while maintaining the operating flow rate within the 
specified limits.
    3.3 Sample period. The required sample period for PM<INF>2.5</INF> 
concentration measurements by this method shall be 1,380 to 1500 minutes 
(23 to 25 hours). However, when a sample period is less than 1,380 
minutes, the measured concentration (as determined by the collected 
PM<INF>2.5</INF> mass divided by the actual sampled air volume), 
multiplied by the actual number of minutes in the sample period and 
divided by 1,440, may be used as if it were a valid concentration 
measurement for the specific purpose of determining a violation of the 
NAAQS. This value assumes that the PM<INF>2.5</INF> concentration is 
zero for the remaining portion of the sample period and therefore 
represents the minimum concentration that could have been measured for 
the full 24-hour sample period. Accordingly, if the value thus 
calculated is high enough to be an exceedance, such an exceedance would 
be a valid exceedance for the sample period. When reported to AIRS, this 
data value should receive a special code to identify it as not to be 
commingled with normal concentration measurements or used for other 
purposes.
    4.0 Accuracy.
    4.1 Because the size and volatility of the particles making up 
ambient particulate matter vary over a wide range and the mass 
concentration of particles varies with particle size, it is difficult to 
define the accuracy of PM<INF>2.5</INF> measurements in an absolute 
sense. The accuracy of PM<INF>2.5</INF> measurements is therefore 
defined in a relative sense, referenced to measurements provided by this 
reference method. Accordingly, accuracy shall be defined as the degree 
of agreement between a subject field PM<INF>2.5</INF> sampler and a 
collocated PM<INF>2.5</INF> reference method audit sampler operating 
simultaneously at the monitoring site location of the subject sampler 
and includes both random (precision) and systematic (bias) errors. The 
requirements for this field sampler audit procedure are set forth in 
part 58, appendix A of this chapter.
    4.2 Measurement system bias. Results of collocated measurements 
where the duplicate sampler is a reference method sampler are used to 
assess a portion of the measurement system bias according to the 
schedule and procedure specified in part 58, appendix A of this chapter.
    4.3 Audits with reference method samplers to determine system 
accuracy and bias. According to the schedule and procedure specified in 
part 58, appendix A of this chapter, a reference method sampler is 
required to be located at each of selected PM<INF>2.5</INF> SLAMS sites 
as a duplicate sampler. The results from the primary sampler and the 
duplicate reference method sampler are used to calculate accuracy of the 
primary sampler on a quarterly

[[Page 75]]

basis, bias of the primary sampler on an annual basis, and bias of a 
single reporting organization on an annual basis. Reference 2 in section 
13.0 of this appendix provides additional information and guidance on 
these reference method audits.
    4.4 Flow rate accuracy and bias. Part 58, appendix A of this chapter 
requires that the flow rate accuracy and bias of individual 
PM<INF>2.5</INF> samplers used in SLAMS monitoring networks be assessed 
periodically via audits of each sampler's operational flow rate. In 
addition, part 58, appendix A of this chapter requires that flow rate 
bias for each reference and equivalent method operated by each reporting 
organization be assessed quarterly and annually. Reference 2 in section 
13.0 of this appendix provides additional information and guidance on 
flow rate accuracy audits and calculations for accuracy and bias.
    5.0 Precision. A data quality objective of 10 percent coefficient of 
variation or better has been established for the operational precision 
of PM<INF>2.5</INF> monitoring data.
    5.1 Tests to establish initial operational precision for each 
reference method sampler are specified as a part of the requirements for 
designation as a reference method under Sec. 53.58 of this chapter.
    5.2 Measurement System Precision. Collocated sampler results, where 
the duplicate sampler is not a reference method sampler but is a sampler 
of the same designated method as the primary sampler, are used to assess 
measurement system precision according to the schedule and procedure 
specified in part 58, appendix A of this chapter. Part 58, appendix A of 
this chapter requires that these collocated sampler measurements be used 
to calculate quarterly and annual precision estimates for each primary 
sampler and for each designated method employed by each reporting 
organization. Reference 2 in section 13.0 of this appendix provides 
additional information and guidance on this requirement.
    6.0 Filter for PM<INF>2.5</INF> Sample Collection. Any filter 
manufacturer or vendor who sells or offers to sell filters specifically 
identified for use with this PM<INF>2.5</INF> reference method shall 
certify that the required number of filters from each lot of filters 
offered for sale as such have been tested as specified in this section 
6.0 and meet all of the following design and performance specifications.
    6.1 Size. Circular, 46.2 mm diameter +\0.25 mm.
    6.2 Medium. Polytetrafluoroethylene (PTFE Teflon), with integral 
support ring.
    6.3 Support ring. Polymethylpentene (PMP) or equivalent inert 
material, 0.38 +\0.04 mm thick, outer diameter 46.2 mm +\0.25 mm, and 
width of 3.68 mm ( +\0.00, -0.51 mm).
    6.4 Pore size. 2 <greek mu<ls-thn-eq>m as measured by ASTM F 316-94.
    6.5 Filter thickness. 30 to 50 <greek mu<ls-thn-eq>m.
    6.6 Maximum pressure drop (clean filter). 30 cm H<INF>2</INF>O 
column @ 16.67 L/min clean air flow.
    6.7 Maximum moisture pickup. Not more than 10 <greek mu<ls-thn-eq>g 
weight increase after 24-hour exposure to air of 40 percent relative 
humidity, relative to weight after 24-hour exposure to air of 35 percent 
relative humidity.
    6.8 Collection efficiency. Greater than 99.7 percent, as measured by 
the DOP test (ASTM D 2986-91) with 0.3 <greek mu<ls-thn-eq>m particles 
at the sampler's operating face velocity.
    6.9 Filter weight stability. Filter weight loss shall be less than 
20 <greek mu<ls-thn-eq>g, as measured in each of the following two tests 
specified in sections 6.9.1 and 6.9.2 of this appendix. The following 
conditions apply to both of these tests: Filter weight loss shall be the 
average difference between the initial and the final filter weights of a 
random sample of test filters selected from each lot prior to sale. The 
number of filters tested shall be not less than 0.1 percent of the 
filters of each manufacturing lot, or 10 filters, whichever is greater. 
The filters shall be weighed under laboratory conditions and shall have 
had no air sample passed through them, i.e., filter blanks. Each test 
procedure must include initial conditioning and weighing, the test, and 
final conditioning and weighing. Conditioning and weighing shall be in 
accordance with sections 8.0 through 8.2 of this appendix and general 
guidance provided in reference 2 of section 13.0 of this appendix.
    6.9.1 Test for loose, surface particle contamination. After the 
initial weighing, install each test filter, in turn, in a filter 
cassette (Figures L-27, L-28, and L-29 of this appendix) and drop the 
cassette from a height of 25 cm to a flat hard surface, such as a 
particle-free wood bench. Repeat two times, for a total of three drop 
tests for each test filter. Remove the test filter from the cassette and 
weigh the filter. The average change in weight must be less than 20 
<greek mu<ls-thn-eq>g.
    6.9.2 Test for temperature stability. After weighing each filter, 
place the test filters in a drying oven set at 40  deg.C +\2  deg.C for 
not less than 48 hours. Remove, condition, and reweigh each test filter. 
The average change in weight must be less than 20 <greek mu<ls-thn-eq>g.
    6.10 Alkalinity. Less than 25 microequivalents/gram of filter, as 
measured by the guidance given in reference 2 in section 13.0 of this 
appendix.
    6.11 Supplemental requirements. Although not required for 
determination of PM<INF>2.5</INF> mass concentration under this 
reference method, additional specifications for the filter must be 
developed by users who intend to subject PM<INF>2.5</INF> filter samples 
to subsequent chemical analysis. These supplemental specifications 
include background chemical contamination of the filter and any other 
filter parameters that may be required by the method of chemical 
analysis. All such supplemental filter specifications must be compatible 
with and

[[Page 76]]

secondary to the primary filter specifications given in this section 6.0 
of this appendix.
    7.0 PM<INF>2.5</INF> Sampler.
    7.1 Configuration. The sampler shall consist of a sample air inlet, 
downtube, particle size separator (impactor), filter holder assembly, 
air pump and flow rate control system, flow rate measurement device, 
ambient and filter temperature monitoring system, barometric pressure 
measurement system, timer, outdoor environmental enclosure, and suitable 
mechanical, electrical, or electronic control capability to meet or 
exceed the design and functional performance as specified in this 
section 7.0 of this appendix. The performance specifications require 
that the sampler:
    (a) Provide automatic control of sample volumetric flow rate and 
other operational parameters.
    (b) Monitor these operational parameters as well as ambient 
temperature and pressure.
    (c) Provide this information to the sampler operator at the end of 
each sample period in digital form, as specified in table L-1 of section 
7.4.19 of this appendix.
    7.2 Nature of specifications. The PM<INF>2.5</INF> sampler is 
specified by a combination of design and performance requirements. The 
sample inlet, downtube, particle size discriminator, filter cassette, 
and the internal configuration of the filter holder assembly are 
specified explicitly by design figures and associated mechanical 
dimensions, tolerances, materials, surface finishes, assembly 
instructions, and other necessary specifications. All other aspects of 
the sampler are specified by required operational function and 
performance, and the design of these other aspects (including the design 
of the lower portion of the filter holder assembly) is optional, subject 
to acceptable operational performance. Test procedures to demonstrate 
compliance with both the design and performance requirements are set 
forth in subpart E of part 53 of this chapter.
    7.3 Design specifications. Except as indicated in this section 7.3 
of this appendix, these components must be manufactured or reproduced 
exactly as specified, in an ISO 9001-registered facility, with 
registration initially approved and subsequently maintained during the 
period of manufacture. See Sec. 53.1(t) of this chapter for the 
definition of an ISO-registered facility. Minor modifications or 
variances to one or more components that clearly would not affect the 
aerodynamic performance of the inlet, downtube, impactor, or filter 
cassette will be considered for specific approval. Any such proposed 
modifications shall be described and submitted to the EPA for specific 
individual acceptability either as part of a reference or equivalent 
method application under part 53 of this chapter or in writing in 
advance of such an intended application under part 53 of this chapter.
    7.3.1 Sample inlet assembly. The sample inlet assembly, consisting 
of the inlet, downtube, and impactor shall be configured and assembled 
as indicated in Figure L-1 of this appendix and shall meet all 
associated requirements. A portion of this assembly shall also be 
subject to the maximum overall sampler leak rate specification under 
section 7.4.6 of this appendix.
    7.3.2 Inlet. The sample inlet shall be fabricated as indicated in 
Figures L-2 through L-18 of this appendix and shall meet all associated 
requirements.
    7.3.3 Downtube. The downtube shall be fabricated as indicated in 
Figure L-19 of this appendix and shall meet all associated requirements.
    7.3.4 Impactor.
    7.3.4.1 The impactor (particle size separator) shall be fabricated 
as indicated in Figures L-20 through L-24 of this appendix and shall 
meet all associated requirements. Following the manufacture and 
finishing of each upper impactor housing (Figure L-21 of this appendix), 
the dimension of the impaction jet must be verified by the manufacturer 
using Class ZZ go/no-go plug gauges that are traceable to NIST.
    7.3.4.2 Impactor filter specifications:
    (a) Size. Circular, 35 to 37 mm diameter.
    (b) Medium. Borosilicate glass fiber, without binder.
    (c) Pore size. 1 to 1.5 micrometer, as measured by ASTM F 316-80.
    (d) Thickness. 300 to 500 micrometers.
    7.3.4.3 Impactor oil specifications:
    (a) Composition. Tetramethyltetraphenyltrisiloxane, single-compound 
diffusion oil.
    (b) Vapor pressure. Maximum 2 x 10<SUP>-8</SUP> mm Hg at 25  deg.C.
    (c) Viscosity. 36 to 40 centistokes at 25  deg.C.
    (d) Density. 1.06 to 1.07 g/cm\3\ at 25  deg.C.
    (e) Quantity. 1 mL +\0.1 mL.
    7.3.5 Filter holder assembly. The sampler shall have a sample filter 
holder assembly to adapt and seal to the down tube and to hold and seal 
the specified filter, under section 6.0 of this appendix, in the sample 
air stream in a horizontal position below the downtube such that the 
sample air passes downward through the filter at a uniform face 
velocity. The upper portion of this assembly shall be fabricated as 
indicated in Figures L-25 and L-26 of this appendix and shall accept and 
seal with the filter cassette, which shall be fabricated as indicated in 
Figures L-27 through L-29 of this appendix.
    (a) The lower portion of the filter holder assembly shall be of a 
design and construction that:
    (1) Mates with the upper portion of the assembly to complete the 
filter holder assembly,
    (2) Completes both the external air seal and the internal filter 
cassette seal such that all seals are reliable over repeated filter 
changings, and

[[Page 77]]

    (3) Facilitates repeated changing of the filter cassette by the 
sampler operator.
    (b) Leak-test performance requirements for the filter holder 
assembly are included in section 7.4.6 of this appendix.
    (c) If additional or multiple filters are stored in the sampler as 
part of an automatic sequential sample capability, all such filters, 
unless they are currently and directly installed in a sampling channel 
or sampling configuration (either active or inactive), shall be covered 
or (preferably) sealed in such a way as to:
    (1) Preclude significant exposure of the filter to possible 
contamination or accumulation of dust, insects, or other material that 
may be present in the ambient air, sampler, or sampler ventilation air 
during storage periods either before or after sampling; and
    (2) To minimize loss of volatile or semi-volatile PM sample 
components during storage of the filter following the sample period.
    7.3.6 Flow rate measurement adapter. A flow rate measurement adapter 
as specified in Figure L-30 of this appendix shall be furnished with 
each sampler.
    7.3.7 Surface finish. All internal surfaces exposed to sample air 
prior to the filter shall be treated electrolytically in a sulfuric acid 
bath to produce a clear, uniform anodized surface finish of not less 
than 1000 mg/ft<SUP>2</SUP> (1.08 mg/cm<SUP>2</SUP>) in accordance with 
military standard specification (mil. spec.) 8625F, Type II, Class 1 in 
reference 4 of section 13.0 of this appendix. This anodic surface 
coating shall not be dyed or pigmented. Following anodization, the 
surfaces shall be sealed by immersion in boiling deionized water for not 
less than 15 minutes. Section 53.51(d)(2) of this chapter should also be 
consulted.
    7.3.8 Sampling height. The sampler shall be equipped with legs, a 
stand, or other means to maintain the sampler in a stable, upright 
position and such that the center of the sample air entrance to the 
inlet, during sample collection, is maintained in a horizontal plane and 
is 2.0 +\0.2 meters above the floor or other horizontal supporting 
surface. Suitable bolt holes, brackets, tie-downs, or other means should 
be provided to facilitate mechanically securing the sample to the 
supporting surface to prevent toppling of the sampler due to wind.
    7.4 Performance specifications.
    7.4.1 Sample flow rate. Proper operation of the impactor requires 
that specific air velocities be maintained through the device. 
Therefore, the design sample air flow rate through the inlet shall be 
16.67 L/min (1.000 m\3\/hour) measured as actual volumetric flow rate at 
the temperature and pressure of the sample air entering the inlet.
    7.4.2 Sample air flow rate control system. The sampler shall have a 
sample air flow rate control system which shall be capable of providing 
a sample air volumetric flow rate within the specified range, under 
section 7.4.1 of this appendix, for the specified filter, under section 
6.0 of this appendix, at any atmospheric conditions specified, under 
section 7.4.7 of this appendix, at a filter pressure drop equal to that 
of a clean filter plus up to 75 cm water column (55 mm Hg), and over the 
specified range of supply line voltage, under section 7.4.15.1 of this 
appendix. This flow control system shall allow for operator adjustment 
of the operational flow rate of the sampler over a range of at least 
+\15 percent of the flow rate specified in section 7.4.1 of this 
appendix.
    7.4.3 Sample flow rate regulation. The sample flow rate shall be 
regulated such that for the specified filter, under section 6.0 of this 
appendix, at any atmospheric conditions specified, under section 7.4.7 
of this appendix, at a filter pressure drop equal to that of a clean 
filter plus up to 75 cm water column (55 mm Hg), and over the specified 
range of supply line voltage, under section 7.4.15.1 of this appendix, 
the flow rate is regulated as follows:
    7.4.3.1 The volumetric flow rate, measured or averaged over 
intervals of not more than 5 minutes over a 24-hour period, shall not 
vary more than +\5 percent from the specified 16.67 L/min flow rate over 
the entire sample period.
    7.4.3.2 The coefficient of variation (sample standard deviation 
divided by the mean) of the flow rate, measured over a 24-hour period, 
shall not be greater than 2 percent.
    7.4.3.3 The amplitude of short-term flow rate pulsations, such as 
may originate from some types of vacuum pumps, shall be attenuated such 
that they do not cause significant flow measurement error or affect the 
collection of particles on the particle collection filter.
    7.4.4 Flow rate cut off. The sampler's sample air flow rate control 
system shall terminate sample collection and stop all sample flow for 
the remainder of the sample period in the event that the sample flow 
rate deviates by more than 10 percent from the sampler design flow rate 
specified in section 7.4.1 of this appendix for more than 60 seconds. 
However, this sampler cut-off provision shall not apply during periods 
when the sampler is inoperative due to a temporary power interruption, 
and the elapsed time of the inoperative period shall not be included in 
the total sample time measured and reported by the sampler, under 
section 7.4.13 of this appendix.
    7.4.5 Flow rate measurement.
    7.4.5.1 The sampler shall provide a means to measure and indicate 
the instantaneous sample air flow rate, which shall be measured as 
volumetric flow rate at the temperature and pressure of the sample air 
entering the inlet, with an accuracy of +\2 percent. The measured flow 
rate shall be available for display to the sampler operator at any time 
in either sampling or standby modes, and the measurement shall be 
updated at least every 30 seconds. The sampler shall also provide a

[[Page 78]]

simple means by which the sampler operator can manually start the sample 
flow temporarily during non-sampling modes of operation, for the purpose 
of checking the sample flow rate or the flow rate measurement system.
    7.4.5.2 During each sample period, the sampler's flow rate 
measurement system shall automatically monitor the sample volumetric 
flow rate, obtaining flow rate measurements at intervals of not greater 
than 30 seconds.
    (a) Using these interval flow rate measurements, the sampler shall 
determine or calculate the following flow-related parameters, scaled in 
the specified engineering units:
    (1) The instantaneous or interval-average flow rate, in L/min.
    (2) The value of the average sample flow rate for the sample period, 
in L/min.
    (3) The value of the coefficient of variation (sample standard 
deviation divided by the average) of the sample flow rate for the sample 
period, in percent.
    (4) The occurrence of any time interval during the sample period in 
which the measured sample flow rate exceeds a range of +\5 percent of 
the average flow rate for the sample period for more than 5 minutes, in 
which case a warning flag indicator shall be set.
    (5) The value of the integrated total sample volume for the sample 
period, in m\3\.
    (b) Determination or calculation of these values shall properly 
exclude periods when the sampler is inoperative due to temporary 
interruption of electrical power, under section 7.4.13 of this appendix, 
or flow rate cut off, under section 7.4.4 of this appendix.
    (c) These parameters shall be accessible to the sampler operator as 
specified in table L-1 of section 7.4.19 of this appendix. In addition, 
it is strongly encouraged that the flow rate for each 5-minute interval 
during the sample period be available to the operator following the end 
of the sample period.
    7.4.6 Leak test capability.
    7.4.6.1 External leakage. The sampler shall include an external air 
leak-test capability consisting of components, accessory hardware, 
operator interface controls, a written procedure in the associated 
Operation/Instruction Manual, under section 7.4.18 of this appendix, and 
all other necessary functional capability to permit and facilitate the 
sampler operator to conveniently carry out a leak test of the sampler at 
a field monitoring site without additional equipment. The sampler 
components to be subjected to this leak test include all components and 
their interconnections in which external air leakage would or could 
cause an error in the sampler's measurement of the total volume of 
sample air that passes through the sample filter.
    (a) The suggested technique for the operator to use for this leak 
test is as follows:
    (1) Remove the sampler inlet and installs the flow rate measurement 
adapter supplied with the sampler, under section 7.3.6 of this appendix.
    (2) Close the valve on the flow rate measurement adapter and use the 
sampler air pump to draw a partial vacuum in the sampler, including (at 
least) the impactor, filter holder assembly (filter in place), flow 
measurement device, and interconnections between these devices, of at 
least 55 mm Hg (75 cm water column), measured at a location downstream 
of the filter holder assembly.
    (3) Plug the flow system downstream of these components to isolate 
the components under vacuum from the pump, such as with a built-in 
valve.
    (4) Stop the pump.
    (5) Measure the trapped vacuum in the sampler with a built-in 
pressure measuring device.
    (6) (i) Measure the vacuum in the sampler with the built-in pressure 
measuring device again at a later time at least 10 minutes after the 
first pressure measurement.
    (ii) Caution: Following completion of the test, the adaptor valve 
should be opened slowly to limit the flow rate of air into the sampler. 
Excessive air flow rate may blow oil out of the impactor.
    (7) Upon completion of the test, open the adaptor valve, remove the 
adaptor and plugs, and restore the sampler to the normal operating 
configuration.
    (b) The associated leak test procedure shall require that for 
successful passage of this test, the difference between the two pressure 
measurements shall not be greater than the number of mm of Hg specified 
for the sampler by the manufacturer, based on the actual internal volume 
of the sampler, that indicates a leak of less than 80 mL/min.
    (c) Variations of the suggested technique or an alternative external 
leak test technique may be required for samplers whose design or 
configuration would make the suggested technique impossible or 
impractical. The specific proposed external leak test procedure, or 
particularly an alternative leak test technique, proposed for a 
particular candidate sampler may be described and submitted to the EPA 
for specific individual acceptability either as part of a reference or 
equivalent method application under part 53 of this chapter or in 
writing in advance of such an intended application under part 53 of this 
chapter.
    7.4.6.2 Internal, filter bypass leakage. The sampler shall include 
an internal, filter bypass leak-check capability consisting of 
components, accessory hardware, operator interface controls, a written 
procedure in the Operation/Instruction Manual, and all other necessary 
functional capability to permit and facilitate the sampler operator to 
conveniently carry out a test for internal filter bypass leakage in the 
sampler at a field

[[Page 79]]

monitoring site without additional equipment. The purpose of the test is 
to determine that any portion of the sample flow rate that leaks past 
the sample filter without passing through the filter is insignificant 
relative to the design flow rate for the sampler.
    (a) The suggested technique for the operator to use for this leak 
test is as follows:
    (1) Carry out an external leak test as provided under section 
7.4.6.1 of this appendix which indicates successful passage of the 
prescribed external leak test.
    (2) Install a flow-impervious membrane material in the filter 
cassette, either with or without a filter, as appropriate, which 
effectively prevents air flow through the filter.
    (3) Use the sampler air pump to draw a partial vacuum in the 
sampler, downstream of the filter holder assembly, of at least 55 mm Hg 
(75 cm water column).
    (4) Plug the flow system downstream of the filter holder to isolate 
the components under vacuum from the pump, such as with a built-in 
valve.
    (5) Stop the pump.
    (6) Measure the trapped vacuum in the sampler with a built-in 
pressure measuring device.
    (7) Measure the vacuum in the sampler with the built-in pressure 
measuring device again at a later time at least 10 minutes after the 
first pressure measurement.
    (8) Remove the flow plug and membrane and restore the sampler to the 
normal operating configuration.
    (b) The associated leak test procedure shall require that for 
successful passage of this test, the difference between the two pressure 
measurements shall not be greater than the number of mm of Hg specified 
for the sampler by the manufacturer, based on the actual internal volume 
of the portion of the sampler under vacuum, that indicates a leak of 
less than 80 mL/min.
    (c) Variations of the suggested technique or an alternative 
internal, filter bypass leak test technique may be required for samplers 
whose design or configuration would make the suggested technique 
impossible or impractical. The specific proposed internal leak test 
procedure, or particularly an alternative internal leak test technique 
proposed for a particular candidate sampler may be described and 
submitted to the EPA for specific individual acceptability either as 
part of a reference or equivalent method application under part 53 of 
this chapter or in writing in advance of such intended application under 
part 53 of this chapter.
    7.4.7 Range of operational conditions. The sampler is required to 
operate properly and meet all requirements specified in this appendix 
over the following operational ranges.
    7.4.7.1 Ambient temperature. -30 to =45  deg.C (Note: Although for 
practical reasons, the temperature range over which samplers are 
required to be tested under part 53 of this chapter is -20 to =40 
deg.C, the sampler shall be designed to operate properly over this wider 
temperature range.).
    7.4.7.2 Ambient relative humidity. 0 to 100 percent.
    7.4.7.3 Barometric pressure range. 600 to 800 mm Hg.
    7.4.8 Ambient temperature sensor. The sampler shall have capability 
to measure the temperature of the ambient air surrounding the sampler 
over the range of -30 to =45  deg.C, with a resolution of 0.1  deg.C and 
accuracy of +\2.0  deg.C, referenced as described in reference 3 in 
section 13.0 of this appendix, with and without maximum solar 
insolation.
    7.4.8.1 The ambient temperature sensor shall be mounted external to 
the sampler enclosure and shall have a passive, naturally ventilated sun 
shield. The sensor shall be located such that the entire sun shield is 
at least 5 cm above the horizontal plane of the sampler case or 
enclosure (disregarding the inlet and downtube) and external to the 
vertical plane of the nearest side or protuberance of the sampler case 
or enclosure. The maximum temperature measurement error of the ambient 
temperature measurement system shall be less than 1.6  deg.C at 1 m/s 
wind speed and 1000 W/m2 solar radiation intensity.
    7.4.8.2 The ambient temperature sensor shall be of such a design and 
mounted in such a way as to facilitate its convenient dismounting and 
immersion in a liquid for calibration and comparison to the filter 
temperature sensor, under section 7.4.11 of this appendix.
    7.4.8.3 This ambient temperature measurement shall be updated at 
least every 30 seconds during both sampling and standby (non-sampling) 
modes of operation. A visual indication of the current (most recent) 
value of the ambient temperature measurement, updated at least every 30 
seconds, shall be available to the sampler operator during both sampling 
and standby (non-sampling) modes of operation, as specified in table L-1 
of section 7.4.19 of this appendix.
    7.4.8.4 This ambient temperature measurement shall be used for the 
purpose of monitoring filter temperature deviation from ambient 
temperature, as required by section 7.4.11 of this appendix, and may be 
used for purposes of effecting filter temperature control, under section 
7.4.10 of this appendix, or computation of volumetric flow rate, under 
sections 7.4.1 to 7.4.5 of this appendix, if appropriate.
    7.4.8.5 Following the end of each sample period, the sampler shall 
report the maximum, minimum, and average temperature for the sample 
period, as specified in table L-1 of section 7.4.19 of this appendix.
    7.4.9 Ambient barometric sensor. The sampler shall have capability 
to measure the barometric pressure of the air surrounding the

[[Page 80]]

sampler over a range of 600 to 800 mm Hg referenced as described in 
reference 3 in section 13.0 of this appendix; also see part 53, subpart 
E of this chapter. This barometric pressure measurement shall have a 
resolution of 5 mm Hg and an accuracy of +\10 mm Hg and shall be updated 
at least every 30 seconds. A visual indication of the value of the 
current (most recent) barometric pressure measurement, updated at least 
every 30 seconds, shall be available to the sampler operator during both 
sampling and standby (non-sampling) modes of operation, as specified in 
table L-1 of section 7.4.19 of this appendix. This barometric pressure 
measurement may be used for purposes of computation of volumetric flow 
rate, under sections 7.4.1 to 7.4.5 of this appendix, if appropriate. 
Following the end of a sample period, the sampler shall report the 
maximum, minimum, and mean barometric pressures for the sample period, 
as specified in table L-1 of section 7.4.19 of this appendix.
    7.4.10 Filter temperature control (sampling and post-sampling). The 
sampler shall provide a means to limit the temperature rise of the 
sample filter (all sample filters for sequential samplers), from 
insolation and other sources, to no more 5  deg.C above the temperature 
of the ambient air surrounding the sampler, during both sampling and 
post-sampling periods of operation. The post-sampling period is the non-
sampling period between the end of the active sampling period and the 
time of retrieval of the sample filter by the sampler operator.
    7.4.11 Filter temperature sensor(s).
    7.4.11.1 The sampler shall have the capability to monitor the 
temperature of the sample filter (all sample filters for sequential 
samplers) over the range of -30 to =45  deg.C during both sampling and 
non-sampling periods. While the exact location of this temperature 
sensor is not explicitly specified, the filter temperature measurement 
system must demonstrate agreement, within 1  deg.C, with a test 
temperature sensor located within 1 cm of the center of the filter 
downstream of the filter during both sampling and non-sampling modes, as 
specified in the filter temperature measurement test described in part 
53, subpart E of this chapter. This filter temperature measurement shall 
have a resolution of 0.1  deg.C and accuracy of +\1.0  deg.C, referenced 
as described in reference 3 in section 13.0 of this appendix. This 
temperature sensor shall be of such a design and mounted in such a way 
as to facilitate its reasonably convenient dismounting and immersion in 
a liquid for calibration and comparison to the ambient temperature 
sensor under section 7.4.8 of this appendix.
    7.4.11.2 The filter temperature measurement shall be updated at 
least every 30 seconds during both sampling and standby (non-sampling) 
modes of operation. A visual indication of the current (most recent) 
value of the filter temperature measurement, updated at least every 30 
seconds, shall be available to the sampler operator during both sampling 
and standby (non-sampling) modes of operation, as specified in table L-1 
of section 7.4.19 of this appendix.
    7.4.11.3 For sequential samplers, the temperature of each filter 
shall be measured individually unless it can be shown, as specified in 
the filter temperature measurement test described in Sec. 53.57 of this 
chapter, that the temperature of each filter can be represented by fewer 
temperature sensors.
    7.4.11.4 The sampler shall also provide a warning flag indicator 
following any occurrence in which the filter temperature (any filter 
temperature for sequential samplers) exceeds the ambient temperature by 
more than 5  deg.C for more than 30 consecutive minutes during either 
the sampling or post-sampling periods of operation, as specified in 
table L-1 of section 7.4.19 of this appendix, under section 10.12 of 
this appendix, regarding sample validity when a warning flag occurs. It 
is further recommended (not required) that the sampler be capable of 
recording the maximum differential between the measured filter 
temperature and the ambient temperature and its time and date of 
occurrence during both sampling and post-sampling (non-sampling) modes 
of operation and providing for those data to be accessible to the 
sampler operator following the end of the sample period, as suggested in 
table L-1 of section 7.4.19 of this appendix.
    7.4.12 Clock/timer system.
    (a) The sampler shall have a programmable real-time clock timing/
control system that:
    (1) Is capable of maintaining local time and date, including year, 
month, day-of-month, hour, minute, and second to an accuracy of +\1.0 
minute per month.
    (2) Provides a visual indication of the current system time, 
including year, month, day-of-month, hour, and minute, updated at least 
each minute, for operator verification.
    (3) Provides appropriate operator controls for setting the correct 
local time and date.
    (4) Is capable of starting the sample collection period and sample 
air flow at a specific, operator-settable time and date, and stopping 
the sample air flow and terminating the sampler collection period 24 
hours (1440 minutes) later, or at a specific, operator-settable time and 
date.
    (b) These start and stop times shall be readily settable by the 
sampler operator to within +\1.0 minute. The system shall provide a 
visual indication of the current start and stop time settings, readable 
to +\1.0 minute, for verification by the operator, and the start and 
stop times shall also be available via the data output port, as 
specified in table L-1 of section 7.4.19 of this appendix. Upon 
execution of a programmed sample period start, the sampler shall 
automatically reset all sample period information and warning

[[Page 81]]

flag indications pertaining to a previous sample period. Refer also to 
section 7.4.15.4 of this appendix regarding retention of current date 
and time and programmed start and stop times during a temporary 
electrical power interruption.
    7.4.13 Sample time determination. The sampler shall be capable of 
determining the elapsed sample collection time for each PM<INF>2.5</INF> 
sample, accurate to within +\1.0 minute, measured as the time between 
the start of the sampling period, under section 7.4.12 of this appendix 
and the termination of the sample period, under section 7.4.12 of this 
appendix or section 7.4.4 of this appendix. This elapsed sample time 
shall not include periods when the sampler is inoperative due to a 
temporary interruption of electrical power, under section 7.4.15.4 of 
this appendix. In the event that the elapsed sample time determined for 
the sample period is not within the range specified for the required 
sample period in section 3.3 of this appendix, the sampler shall set a 
warning flag indicator. The date and time of the start of the sample 
period, the value of the elapsed sample time for the sample period, and 
the flag indicator status shall be available to the sampler operator 
following the end of the sample period, as specified in table L-1 of 
section 7.4.19 of this appendix.
    7.4.14 Outdoor environmental enclosure. The sampler shall have an 
outdoor enclosure (or enclosures) suitable to protect the filter and 
other non-weatherproof components of the sampler from precipitation, 
wind, dust, extremes of temperature and humidity; to help maintain 
temperature control of the filter (or filters, for sequential samplers); 
and to provide reasonable security for sampler components and settings.
    7.4.15 Electrical power supply.
    7.4.15.1 The sampler shall be operable and function as specified 
herein when operated on an electrical power supply voltage of 105 to 125 
volts AC (RMS) at a frequency of 59 to 61 Hz. Optional operation as 
specified at additional power supply voltages and/or frequencies shall 
not be precluded by this requirement.
    7.4.15.2 The design and construction of the sampler shall comply 
with all applicable National Electrical Code and Underwriters 
Laboratories electrical safety requirements.
    7.4.15.3 The design of all electrical and electronic controls shall 
be such as to provide reasonable resistance to interference or 
malfunction from ordinary or typical levels of stray electromagnetic 
fields (EMF) as may be found at various monitoring sites and from 
typical levels of electrical transients or electronic noise as may often 
or occasionally be present on various electrical power lines.
    7.4.15.4 In the event of temporary loss of electrical supply power 
to the sampler, the sampler shall not be required to sample or provide 
other specified functions during such loss of power, except that the 
internal clock/timer system shall maintain its local time and date 
setting within +\1 minute per week, and the sampler shall retain all 
other time and programmable settings and all data required to be 
available to the sampler operator following each sample period for at 
least 7 days without electrical supply power. When electrical power is 
absent at the operator-set time for starting a sample period or is 
interrupted during a sample period, the sampler shall automatically 
start or resume sampling when electrical power is restored, if such 
restoration of power occurs before the operator-set stop time for the 
sample period.
    7.4.15.5 The sampler shall have the capability to record and retain 
a record of the year, month, day-of-month, hour, and minute of the start 
of each power interruption of more than 1 minute duration, up to 10 such 
power interruptions per sample period. (More than 10 such power 
interruptions shall invalidate the sample, except where an exceedance is 
measured, under section 3.3 of this appendix.) The sampler shall provide 
for these power interruption data to be available to the sampler 
operator following the end of the sample period, as specified in table 
L-1 of section 7.4.19 of this appendix.
    7.4.16 Control devices and operator interface. The sampler shall 
have mechanical, electrical, or electronic controls, control devices, 
electrical or electronic circuits as necessary to provide the timing, 
flow rate measurement and control, temperature control, data storage and 
computation, operator interface, and other functions specified. 
Operator-accessible controls, data displays, and interface devices shall 
be designed to be simple, straightforward, reliable, and easy to learn, 
read, and operate under field conditions. The sampler shall have 
provision for operator input and storage of up to 64 characters of 
numeric (or alphanumeric) data for purposes of site, sampler, and sample 
identification. This information shall be available to the sampler 
operator for verification and change and for output via the data output 
port along with other data following the end of a sample period, as 
specified in table L-1 of section 7.4.19 of this appendix. All data 
required to be available to the operator following a sample collection 
period or obtained during standby mode in a post-sampling period shall 
be retained by the sampler until reset, either manually by the operator 
or automatically by the sampler upon initiation of a new sample 
collection period.
    7.4.17 Data output port requirement. The sampler shall have a 
standard RS-232C data output connection through which digital data may 
be exported to an external data storage or transmission device. All 
information which is required to be available at the end of each sample 
period shall be accessible

[[Page 82]]

through this data output connection. The information that shall be 
accessible though this output port is summarized in table L-1 of section 
7.4.19 of this appendix. Since no specific format for the output data is 
provided, the sampler manufacturer or vendor shall make available to 
sampler purchasers appropriate computer software capable of receiving 
exported sampler data and correctly translating the data into a standard 
spreadsheet format and optionally any other formats as may be useful to 
sampler users. This requirement shall not preclude the sampler from 
offering other types of output connections in addition to the required 
RS-232C port.
    7.4.18 Operation/instruction manual. The sampler shall include an 
associated comprehensive operation or instruction manual, as required by 
part 53 of this chapter, which includes detailed operating instructions 
on the setup, operation, calibration, and maintenance of the sampler. 
This manual shall provide complete and detailed descriptions of the 
operational and calibration procedures prescribed for field use of the 
sampler and all instruments utilized as part of this reference method. 
The manual shall include adequate warning of potential safety hazards 
that may result from normal use or malfunction of the method and a 
description of necessary safety precautions. The manual shall also 
include a clear description of all procedures pertaining to 
installation, operation, periodic and corrective maintenance, and 
troubleshooting, and shall include parts identification diagrams.
    7.4.19 Data reporting requirements. The various information that the 
sampler is required to provide and how it is to be provided is 
summarized in the following table L-1.

                                             Table L-1--Summary of Information To Be Provided By the Sampler
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                             Availability                                        Format
                                    Appendix L section -------------------------------------------------------------------------------------------------
    Information to be provided          reference                        End of        Visual      Data output
                                                          Anytime 1     period 2     display\3\         4        Digital reading 5          Units
--------------------------------------------------------------------------------------------------------------------------------------------------------
Flow rate, 30-second maximum       7.4.5.1............      <check>   ............      <check>             *   XX.X...............  L/min
 interval.
Flow rate, average for the sample  7.4.5.2............            *       <check>             *       <check>   XX.X...............  L/min
 period.
Flow rate, CV, for sample period.  7.4.5.2............            *       <check>             *   <check><box>  XX.X...............  %
Flow rate, 5-min. average out of   7.4.5.2............      <check>       <check>       <check>   <check><box>  On/Off.............  ...................
 spec. (FLAG<SUP>6</SUP>).
Sample volume, total.............  7.4.5.2............            *       <check>       <check>   <check><box>  XX.X...............  m\3\
Temperature, ambient, 30-second    7.4.8..............      <check>   ............      <check>   ............  XX.X...............    deg.C
 interval.
Temperature, ambient, min., max.,  7.4.8..............            *       <check>       <check>   <check><box>  XX.X...............    deg.C
 average for the sample period.
Baro pressure, ambient, 30-second  7.4.9..............      <check>   ............      <check>   ............  XXX................  mm Hg
 interval.
Baro pressure, ambient, min.,      7.4.9..............            *       <check>       <check>   <check><box>  XXX................  mm Hg
 max., average for the sample
 period.
Filter temperature, 30-second      7.4.11.............      <check>   ............      <check>   ............  XX.X...............    deg.C
 interval.
Filter temperature differential,   7.4.11.............            *       <check>       <check>   <check><box>  On/Off.............  ...................
 30-second interval, out of spec.
 (FLAG<SUP>6</SUP>).
Filter temperature, maximum        7.4.11.............            *             *             *             *   X.X, YY/MM/DD HH:mm    deg.C, Yr./Mon./
 differential from ambient, date,                                                                                                     Day Hrs. min
 time of occurrence.

[[Page 83]]

Date and time....................  7.4.12.............      <check>   ............      <check>   ............  YY/MM/DD HH:mm.....  Yr./Mon./Day Hrs.
                                                                                                                                      min
Sample start and stop time         7.4.12.............      <check>       <check>       <check>       <check>   YY/MM/DD HH:mm.....  Yr./Mon./Day Hrs.
 settings.                                                                                                                            min
Sample period start time.........  7.4.12.............  ............      <check>       <check>   <check><box>  YYYY/MM/DD HH:mm...  Yr./Mon./Day Hrs.
                                                                                                                                      min
Elapsed sample time..............  7.4.13.............            *       <check>       <check>   <check><box>  HH:mm..............  Hrs. min
Elapsed sample time, out of spec.  7.4.13.............  ............      <check>       <check>   <check><box>  On/Off.............  ...................
 (FLAG<SUP>6</SUP>).
Power interruptions </=1 min.,     7.4.15.5...........            *       <check>             *       <check>   1HH:mm, 2HH:mm, etc  Hrs. min
 start time of first 10.                                                                                         ....
User-entered information, such as  7.4.16.............      <check>       <check>       <check>   <check><box>  As entered.........  ...................
 sampler and site identification.
--------------------------------------------------------------------------------------------------------------------------------------------------------
<check> Provision of this information is required.
*Provision of this information is optional. If information related to the entire sample period is optionally provided prior to the end of the sample
  period, the value provided should be the value calculated for the portion of the sampler period completed up to the time the information is provided.
<box> Indicates that this information is also required to be provided to the AIRS data bank; see Sec.  Sec.  58.26 and 58.35 of this chapter.

<SUP>1</SUP> Information is required to be available to the operator at any time the sampler is operating, whether sampling or not.
<SUP>2</SUP> Information relates to the entire sampler period and must be provided following the end of the sample period until reset manually by the operator or
  automatically by the sampler upon the start of a new sample period.
\3\ Information shall be available to the operator visually.
<SUP>4</SUP> Information is to be available as digital data at the sampler's data output port specified in section 7.4.16 of this appendix following the end of the
  sample period until reset manually by the operator or automatically by the sampler upon the start of a new sample period.
<SUP>5</SUP> Digital readings, both visual and data output, shall have not less than the number of significant digits and resolution specified.
<SUP>6</SUP> Flag warnings may be displayed to the operator by a single-flag indicator or each flag may be displayed individually. Only a set (on) flag warning
  must be indicated; an off (unset) flag may be indicated by the absence of a flag warning. Sampler users should refer to section 10.12 of this appendix
  regarding the validity of samples for which the sampler provided an associated flag warning.

    8.0 Filter Weighing. See reference 2 in section 13.0 of this 
appendix, for additional, more detailed guidance.
    8.1 Analytical balance. The analytical balance used to weigh filters 
must be suitable for weighing the type and size of filters specified, 
under section 6.0 of this appendix, and have a readability of +\1 <greek 
mu<ls-thn-eq>g. The balance shall be calibrated as specified by the 
manufacturer at installation and recalibrated immediately prior to each 
weighing session. See reference 2 in section 13.0 of this appendix for 
additional guidance.
    8.2 Filter conditioning. All sample filters used shall be 
conditioned immediately before both the pre- and post-sampling weighings 
as specified below. See reference 2 in section 13.0 of this appendix for 
additional guidance.
    8.2.1 Mean temperature. 20 - 23  deg.C.
    8.2.2 Temperature control. +\2  deg.C over 24 hours.
    8.2.3 Mean humidity. Generally, 30-40 percent relative humidity; 
however, where it can be shown that the mean ambient relative humidity 
during sampling is less than 30 percent, conditioning is permissible at 
a mean relative humidity within +\5 relative humidity percent of the 
mean ambient relative humidity during sampling, but not less than 20 
percent.
    8.2.4 Humidity control. +\5 relative humidity percent over 24 hours.
    8.2.5 Conditioning time. Not less than 24 hours.
    8.3 Weighing procedure.
    8.3.1 New filters should be placed in the conditioning environment 
immediately upon arrival and stored there until the pre-sampling 
weighing. See reference 2 in section 13.0 of this appendix for 
additional guidance.
    8.3.2 The analytical balance shall be located in the same controlled 
environment in which the filters are conditioned. The filters shall be 
weighed immediately following the conditioning period without 
intermediate or transient exposure to other conditions or environments.

[[Page 84]]

    8.3.3 Filters must be conditioned at the same conditions (humidity 
within +\5 relative humidity percent) before both the pre- and post-
sampling weighings.
    8.3.4 Both the pre- and post-sampling weighings should be carried 
out on the same analytical balance, using an effective technique to 
neutralize static charges on the filter, under reference 2 in section 
13.0 of this appendix. If possible, both weighings should be carried out 
by the same analyst.
    8.3.5 The pre-sampling (tare) weighing shall be within 30 days of 
the sampling period.
    8.3.6 The post-sampling conditioning and weighing shall be completed 
within 240 hours (10 days) after the end of the sample period, unless 
the filter sample is maintained at 4  deg.C or less during the entire 
time between retrieval from the sampler and the start of the 
conditioning, in which case the period shall not exceed 30 days. 
Reference 2 in section 13.0 of this appendix has additional guidance on 
transport of cooled filters.
    8.3.7 Filter blanks.
    8.3.7.1 New field blank filters shall be weighed along with the pre-
sampling (tare) weighing of each lot of PM<INF>2.5</INF> filters. These 
blank filters shall be transported to the sampling site, installed in 
the sampler, retrieved from the sampler without sampling, and reweighed 
as a quality control check.
    8.3.7.2 New laboratory blank filters shall be weighed along with the 
pre-sampling (tare) weighing of each set of PM<INF>2.5</INF> filters. 
These laboratory blank filters should remain in the laboratory in 
protective containers during the field sampling and should be reweighed 
as a quality control check.
    8.3.8 Additional guidance for proper filter weighing and related 
quality assurance activities is provided in reference 2 in section 13.0 
of this appendix.
    9.0 Calibration. Reference 2 in section 13.0 of this appendix 
contains additional guidance.
    9.1 General requirements.
    9.1.1 Multipoint calibration and single-point verification of the 
sampler's flow rate measurement device must be performed periodically to 
establish and maintain traceability of subsequent flow measurements to a 
flow rate standard.
    9.1.2 An authoritative flow rate standard shall be used for 
calibrating or verifying the sampler's flow rate measurement device with 
an accuracy of +\2 percent. The flow rate standard shall be a separate, 
stand-alone device designed to connect to the flow rate measurement 
adapter, Figure L-30 of this appendix. This flow rate standard must have 
its own certification and be traceable to a National Institute of 
Standards and Technology (NIST) primary standard for volume or flow 
rate. If adjustments to the sampler's flow rate measurement system 
calibration are to be made in conjunction with an audit of the sampler's 
flow measurement system, such adjustments shall be made following the 
audit. Reference 2 in section 13.0 of this appendix contains additional 
guidance.
    9.1.3 The sampler's flow rate measurement device shall be re-
calibrated after electromechanical maintenance or transport of the 
sampler.
    9.2 Flow rate calibration/verification procedure.
    9.2.1 PM<INF>2.5</INF> samplers may employ various types of flow 
control and flow measurement devices. The specific procedure used for 
calibration or verification of the flow rate measurement device will 
vary depending on the type of flow rate controller and flow rate 
measurement employed. Calibration shall be in terms of actual ambient 
volumetric flow rates (Q<SUP>a</SUP>), measured at the sampler's inlet 
downtube. The generic procedure given here serves to illustrate the 
general steps involved in the calibration of a PM<INF>2.5</INF> sampler. 
The sampler operation/instruction manual required under section 7.4.18 
of this appendix and the Quality Assurance Handbook in reference 2 in 
section 13.0 of this appendix provide more specific and detailed 
guidance for calibration.
    9.2.2 The flow rate standard used for flow rate calibration shall 
have its own certification and be traceable to a NIST primary standard 
for volume or flow rate. A calibration relationship for the flow rate 
standard, e.g., an equation, curve, or family of curves relating actual 
flow rate (Q<INF>a</INF>) to the flow rate indicator reading, shall be 
established that is accurate to within 2 percent over the expected range 
of ambient temperatures and pressures at which the flow rate standard 
may be used. The flow rate standard must be re-calibrated or re-verified 
at least annually.
    9.2.3 The sampler flow rate measurement device shall be calibrated 
or verified by removing the sampler inlet and connecting the flow rate 
standard to the sampler's downtube in accordance with the operation/
instruction manual, such that the flow rate standard accurately measures 
the sampler's flow rate. The sampler operator shall first carry out a 
sampler leak check and confirm that the sampler passes the leak test and 
then verify that no leaks exist between the flow rate standard and the 
sampler.
    9.2.4 The calibration relationship between the flow rate (in actual 
L/min) indicated by the flow rate standard and by the sampler's flow 
rate measurement device shall be established or verified in accordance 
with the sampler operation/instruction manual. Temperature and pressure 
corrections to the flow rate indicated by the flow rate standard may be 
required for certain types of flow rate standards. Calibration of the 
sampler's flow rate measurement device shall consist of at least three 
separate flow rate measurements (multipoint calibration) evenly spaced 
within the range of -10 percent to =10 percent of the sampler's 
operational flow rate, section 7.4.1 of this appendix. Verification of 
the

[[Page 85]]

sampler's flow rate shall consist of one flow rate measurement at the 
sampler's operational flow rate. The sampler operation/instruction 
manual and reference 2 in section 13.0 of this appendix provide 
additional guidance.
    9.2.5 If during a flow rate verification the reading of the 
sampler's flow rate indicator or measurement device differs by +\ 4 
percent or more from the flow rate measured by the flow rate standard, a 
new multipoint calibration shall be performed and the flow rate 
verification must then be repeated.
    9.2.6 Following the calibration or verification, the flow rate 
standard shall be removed from the sampler and the sampler inlet shall 
be reinstalled. Then the sampler's normal operating flow rate (in L/min) 
shall be determined with a clean filter in place. If the flow rate 
indicated by the sampler differs by +\2 percent or more from the 
required sampler flow rate, the sampler flow rate must be adjusted to 
the required flow rate, under section 7.4.1 of this appendix.
    9.3 Periodic calibration or verification of the calibration of the 
sampler's ambient temperature, filter temperature, and barometric 
pressure measurement systems is also required. Reference 3 of section 
13.0 of this appendix contains additional guidance.
    10.0 PM<INF>2.5</INF> Measurement Procedure. The detailed procedure 
for obtaining valid PM<INF>2.5</INF> measurements with each specific 
sampler designated as part of a reference method for PM<INF>2.5</INF> 
under part 53 of this chapter shall be provided in the sampler-specific 
operation or instruction manual required by section 7.4.18 of this 
appendix. Supplemental guidance is provided in section 2.12 of the 
Quality Assurance Handbook listed in reference 2 in section 13.0 of this 
appendix. The generic procedure given here serves to illustrate the 
general steps involved in the PM<INF>2.5</INF> sample collection and 
measurement, using a PM<INF>2.5</INF> reference method sampler.
    10.1 The sampler shall be set up, calibrated, and operated in 
accordance with the specific, detailed guidance provided in the specific 
sampler's operation or instruction manual and in accordance with a 
specific quality assurance program developed and established by the 
user, based on applicable supplementary guidance provided in reference 2 
in section 13.0 of this appendix.
    10.2 Each new sample filter shall be inspected for correct type and 
size and for pinholes, particles, and other imperfections. Unacceptable 
filters should be discarded. A unique identification number shall be 
assigned to each filter, and an information record shall be established 
for each filter. If the filter identification number is not or cannot be 
marked directly on the filter, alternative means, such as a number-
identified storage container, must be established to maintain positive 
filter identification.
    10.3 Each filter shall be conditioned in the conditioning 
environment in accordance with the requirements specified in section 8.2 
of this appendix.
    10.4 Following conditioning, each filter shall be weighed in 
accordance with the requirements specified in section 8.0 of this 
appendix and the presampling weight recorded with the filter 
identification number.
    10.5 A numbered and preweighed filter shall be installed in the 
sampler following the instructions provided in the sampler operation or 
instruction manual.
    10.6 The sampler shall be checked and prepared for sample collection 
in accordance with instructions provided in the sampler operation or 
instruction manual and with the specific quality assurance program 
established for the sampler by the user.
    10.7 The sampler's timer shall be set to start the sample collection 
at the beginning of the desired sample period and stop the sample 
collection 24 hours later.
    10.8 Information related to the sample collection (site location or 
identification number, sample date, filter identification number, and 
sampler model and serial number) shall be recorded and, if appropriate, 
entered into the sampler.
    10.9 The sampler shall be allowed to collect the PM<INF>2.5</INF> 
sample during the set 24-hour time period.
    10.10 Within 96 hours of the end of the sample collection period, 
the filter, while still contained in the filter cassette, shall be 
carefully removed from the sampler, following the procedure provided in 
the sampler operation or instruction manual and the quality assurance 
program, and placed in a protective container. The protective container 
shall contain no loose material that could be transferred to the filter. 
The protective container shall hold the filter cassette securely such 
that the cover shall not come in contact with the filter's surfaces. 
Reference 2 in section 13.0 of this appendix contains additional 
information.
    10.11 The total sample volume in actual m\3\ for the sampling period 
and the elapsed sample time shall be obtained from the sampler and 
recorded in accordance with the instructions provided in the sampler 
operation or instruction manual. All sampler warning flag indications 
and other information required by the local quality assurance program 
shall also be recorded.
    10.12 All factors related to the validity or representativeness of 
the sample, such as sampler tampering or malfunctions, unusual 
meteorological conditions, construction activity, fires or dust storms, 
etc. shall be recorded as required by the local quality assurance 
program. The occurrence of a flag warning during a sample period shall 
not necessarily indicate an invalid sample but rather shall indicate the 
need for specific review

[[Page 86]]

of the QC data by a quality assurance officer to determine sample 
validity.
    10.13 After retrieval from the sampler, the exposed filter 
containing the PM<INF>2.5</INF> sample should be transported to the 
filter conditioning environment as soon as possible ideally to arrive at 
the conditioning environment within 24 hours for conditioning and 
subsequent weighing. During the period between filter retrieval from the 
sampler and the start of the conditioning, the filter shall be 
maintained as cool as practical and continuously protected from exposure 
to temperatures over 25  deg.C. See section 8.3.6 of this appendix 
regarding time limits for completing the post-sampling weighing. See 
reference 2 in section 13.0 of this appendix for additional guidance on 
transporting filter samplers to the conditioning and weighing 
laboratory.
    10.14. The exposed filter containing the PM<INF>2.5</INF> sample 
shall be re-conditioned in the conditioning environment in accordance 
with the requirements specified in section 8.2 of this appendix.
    10.15. The filter shall be reweighed immediately after conditioning 
in accordance with the requirements specified in section 8.0 of this 
appendix, and the postsampling weight shall be recorded with the filter 
identification number.
    10.16 The PM<INF>2.5</INF> concentration shall be calculated as 
specified in section 12.0 of this appendix.
    11.0 Sampler Maintenance. The sampler shall be maintained as 
described by the sampler's manufacturer in the sampler-specific 
operation or instruction manual required under section 7.4.18 of this 
appendix and in accordance with the specific quality assurance program 
developed and established by the user based on applicable supplementary 
guidance provided in reference 2 in section 13.0 of this appendix.
    12.0 Calculations
    12.1 (a) The PM<INF>2.5</INF> concentration is calculated as:

PM<INF>2.5</INF> = (W<INF>f</INF> - W<INF>i</INF>)/V<INF>a</INF>

where:

PM<INF>2.5</INF> = mass concentration of PM<INF>2.5</INF>, <greek 
mu<ls-thn-eq>g/m\3\;
W<INF>f</INF>, W<INF>i</INF> = final and initial weights, respectively, 
of the filter used to collect the PM<INF>2.5</INF> particle sample, 
<greek mu<ls-thn-eq>g;
V<INF>a</INF> = total air volume sampled in actual volume units, as 
provided by the sampler, m\3\.

    Note: Total sample time must be between 1,380 and 1,500 minutes (23 
and 25 hrs) for a fully valid PM<INF>2.5</INF> sample; however, see also 
section 3.3 of this appendix.
    13.0 References.
    1. Quality Assurance Handbook for Air Pollution Measurement Systems, 
Volume I, Principles. EPA/600/R-94/038a, April 1994. Available from 
CERI, ORD Publications, U.S. Environmental Protection Agency, 26 West 
Martin Luther King Drive, Cincinnati, Ohio 45268.
    2. Copies of section 2.12 of the Quality Assurance Handbook for Air 
Pollution Measurement Systems, Volume II, Ambient Air Specific Methods, 
EPA/600/R-94/038b, are available from Department E (MD-77B), U.S. EPA, 
Research Triangle Park, NC 27711.
    3. Quality Assurance Handbook for Air Pollution Measurement Systems, 
Volume IV: Meteorological Measurements, (Revised Edition) EPA/600/R-94/
038d, March, 1995. Available from CERI, ORD Publications, U.S. 
Environmental Protection Agency, 26 West Martin Luther King Drive, 
Cincinnati, Ohio 45268.
    4. Military standard specification (mil. spec.) 8625F, Type II, 
Class 1 as listed in Department of Defense Index of Specifications and 
Standards (DODISS), available from DODSSP-Customer Service, 
Standardization Documents Order Desk, 700 Robbins Avenue, Building 4D, 
Philadelphia, PA 1911-5094.
    14.0 Figures L-1 through L-30 to Appendix L.

[[Page 87]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.022

[[Page 88]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.023

[[Page 89]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.024

[[Page 90]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.025

[[Page 91]]

[GRAPHIC] [TIFF OMITTED] TR17FE98.004

[[Page 92]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.027

[[Page 93]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.028

[[Page 94]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.029

[[Page 95]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.030

[[Page 96]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.031

[[Page 97]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.032

[[Page 98]]

[GRAPHIC] [TIFF OMITTED] TR17FE98.005

[[Page 99]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.034

[[Page 100]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.035

[[Page 101]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.036

[[Page 102]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.037

[[Page 103]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.038

[[Page 104]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.039

[[Page 105]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.040

[[Page 106]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.041

[[Page 107]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.042

[[Page 108]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.043

[[Page 109]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.044

[[Page 110]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.045

[[Page 111]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.046

[[Page 112]]

[GRAPHIC] [TIFF OMITTED] TR17FE98.006

[[Page 113]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.048

[[Page 114]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.049

[[Page 115]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.050

[[Page 116]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.051

[[Page 117]]

[62 FR 38714, July 18, 1997, as amended at 64 FR 19719, Apr. 22, 1999]

    Appendix M to Part 50--Reference Method for the Determination of 
         Particulate Matter as PM<INF>10</INF> in the Atmosphere

    1.0 Applicability.
    1.1 This method provides for the measurement of the mass 
concentration of particulate matter with an aerodynamic diameter less 
than or equal to a nominal 10 micrometers (PM<INF>1O</INF>) in ambient 
air over a 24-hour period for purposes of determining attainment and 
maintenance of the primary and secondary national ambient air quality 
standards for particulate matter specified in Sec. 50.6 of this chapter. 
The measurement process is nondestructive, and the PM<INF>10</INF> 
sample can be subjected to subsequent physical or chemical analyses. 
Quality assurance procedures and guidance are provided in part 58, 
Appendices A and B of this chapter and in references 1 and 2 of section 
12.0 of this appendix.
    2.0 Principle.
    2.1 An air sampler draws ambient air at a constant flow rate into a 
specially shaped inlet where the suspended particulate matter is 
inertially separated into one or more size fractions within the 
PM<INF>10</INF> size range. Each size fraction in the PM<INF>1O</INF> 
size range is then collected on a separate filter over the specified 
sampling period. The particle size discrimination characteristics 
(sampling effectiveness and 50 percent cutpoint) of the sampler inlet 
are prescribed as performance specifications in part 53 of this chapter.
    2.2 Each filter is weighed (after moisture equilibration) before and 
after use to determine the net weight (mass) gain due to collected 
PM<INF>10</INF>. The total volume of air sampled, measured at the actual 
ambient temperature and pressure, is determined from the measured flow 
rate and the sampling time. The mass concentration of PM<INF>10</INF> in 
the ambient air is computed as the total mass of collected particles in 
the PM<INF>10</INF> size range divided by the volume of air sampled, and 
is expressed in micrograms per actual cubic meter (<greek 
mu<ls-thn-eq>g/m\3\).
    2.3 A method based on this principle will be considered a reference 
method only if the associated sampler meets the requirements specified 
in this appendix and the requirements in part 53 of this chapter, and 
the method has been designated as a reference method in accordance with 
part 53 of this chapter.
    3.0 Range.
    3.1 The lower limit of the mass concentration range is determined by 
the repeatability of filter tare weights, assuming the nominal air 
sample volume for the sampler. For samplers having an automatic filter-
changing mechanism, there may be no upper limit. For samplers that do 
not have an automatic filter-changing mechanism, the upper limit is 
determined by the filter mass loading beyond which the sampler no longer 
maintains the operating flow rate within specified limits due to 
increased pressure drop across the loaded filter. This upper limit 
cannot be specified precisely because it is a complex function of the 
ambient particle size distribution and type, humidity, filter type, and 
perhaps other factors. Nevertheless, all samplers should be capable of 
measuring 24-hour PM<INF>10</INF> mass concentrations of at least 300 
<greek mu<ls-thn-eq>g/m\3\ while maintaining the operating flow rate 
within the specified limits.
    4.0 Precision.
    4.1 The precision of PM<INF>10</INF> samplers must be 5 <greek 
mu<ls-thn-eq>g/m\3\ for PM<INF>10</INF> concentrations below 80 <greek 
mu<ls-thn-eq>g/m\3\ and 7 percent for PM<INF>10</INF> concentrations 
above 80 <greek mu<ls-thn-eq>g/m\3\, as required by part 53 of this 
chapter, which prescribes a test procedure that determines the variation 
in the PM<INF>10</INF> concentration measurements of identical samplers 
under typical sampling conditions. Continual assessment of precision via 
collocated samplers is required by part 58 of this chapter for 
PM<INF>10</INF> samplers used in certain monitoring networks.
    5.0 Accuracy.
    5.1 Because the size of the particles making up ambient particulate 
matter varies over a wide range and the concentration of particles 
varies with particle size, it is difficult to define the absolute 
accuracy of PM<INF>10</INF> samplers. Part 53 of this chapter provides a 
specification for the sampling effectiveness of PM<INF>10</INF> 
samplers. This specification requires that the expected mass 
concentration calculated for a candidate PM<INF>10</INF> sampler, when 
sampling a specified particle size distribution, be within +\10 percent 
of that calculated for an ideal sampler whose sampling effectiveness is 
explicitly specified. Also, the particle size for 50 percent sampling 
effectiveness is required to be 10+\0.5 micrometers. Other 
specifications related to accuracy apply to flow measurement and 
calibration, filter media, analytical (weighing) procedures, and 
artifact. The flow rate accuracy of PM<INF>10</INF> samplers used in 
certain monitoring networks is required by part 58 of this chapter to be 
assessed periodically via flow rate audits.
    6.0 Potential Sources of Error.
    6.1 Volatile Particles. Volatile particles collected on filters are 
often lost during shipment and/or storage of the filters prior to the 
post-sampling weighing \3\. Although shipment or storage of loaded 
filters is sometimes unavoidable, filters should be reweighed as soon as 
practical to minimize these losses.
    6.2 Artifacts. Positive errors in PM<INF>10</INF> concentration 
measurements may result from retention of gaseous species on filters 
<SUP>4, 5</SUP>. Such errors include the retention of sulfur dioxide and 
nitric acid. Retention of sulfur

[[Page 118]]

dioxide on filters, followed by oxidation to sulfate, is referred to as 
artifact sulfate formation, a phenomenon which increases with increasing 
filter alkalinity \6\. Little or no artifact sulfate formation should 
occur using filters that meet the alkalinity specification in section 
7.2.4 of this appendix, Artifact nitrate formation, resulting primarily 
from retention of nitric acid, occurs to varying degrees on many filter 
types, including glass fiber, cellulose ester, and many quartz fiber 
filters <SUP>5, 7, 8, 9, 10</SUP>. Loss of true atmospheric particulate 
nitrate during or following sampling may also occur due to dissociation 
or chemical reaction. This phenomenon has been observed on 
Teflon<SUP><register mark<ls-thn-eq></SUP>filters \8\ and inferred for 
quartz fiber filters <SUP>11, 12</SUP>. The magnitude of nitrate 
artifact errors in PM<INF>10</INF> mass concentration measurements will 
vary with location and ambient temperature; however, for most sampling 
locations, these errors are expected to be small.
    6.3 Humidity. The effects of ambient humidity on the sample are 
unavoidable. The filter equilibration procedure in section 9.0 of this 
appendix is designed to minimize the effects of moisture on the filter 
medium.
    6.4 Filter Handling. Careful handling of filters between presampling 
and postsampling weighings is necessary to avoid errors due to damaged 
filters or loss of collected particles from the filters. Use of a filter 
cartridge or cassette may reduce the magnitude of these errors. Filters 
must also meet the integrity specification in section 7.2.3 of this 
appendix.
    6.5 Flow Rate Variation. Variations in the sampler's operating flow 
rate may alter the particle size discrimination characteristics of the 
sampler inlet. The magnitude of this error will depend on the 
sensitivity of the inlet to variations in flow rate and on the particle 
distribution in the atmosphere during the sampling period. The use of a 
flow control device, under section 7.1.3 of this appendix, is required 
to minimize this error.
    6.6 Air Volume Determination. Errors in the air volume determination 
may result from errors in the flow rate and/or sampling time 
measurements. The flow control device serves to minimize errors in the 
flow rate determination, and an elapsed time meter, under section 7.1.5 
of this appendix, is required to minimize the error in the sampling time 
measurement.
    7.0 Apparatus.
    7.1 PM<INF>10</INF> Sampler.
    7.1.1 The sampler shall be designed to:
    (a) Draw the air sample into the sampler inlet and through the 
particle collection filter at a uniform face velocity.
    (b) Hold and seal the filter in a horizontal position so that sample 
air is drawn downward through the filter.
    (c) Allow the filter to be installed and removed conveniently.
    (d) Protect the filter and sampler from precipitation and prevent 
insects and other debris from being sampled.
    (e) Minimize air leaks that would cause error in the measurement of 
the air volume passing through the filter.
    (f) Discharge exhaust air at a sufficient distance from the sampler 
inlet to minimize the sampling of exhaust air.
    (g) Minimize the collection of dust from the supporting surface.
    7.1.2 The sampler shall have a sample air inlet system that, when 
operated within a specified flow rate range, provides particle size 
discrimination characteristics meeting all of the applicable performance 
specifications prescribed in part 53 of this chapter. The sampler inlet 
shall show no significant wind direction dependence. The latter 
requirement can generally be satisfied by an inlet shape that is 
circularly symmetrical about a vertical axis.
    7.1.3 The sampler shall have a flow control device capable of 
maintaining the sampler's operating flow rate within the flow rate 
limits specified for the sampler inlet over normal variations in line 
voltage and filter pressure drop.
    7.1.4 The sampler shall provide a means to measure the total flow 
rate during the sampling period. A continuous flow recorder is 
recommended but not required. The flow measurement device shall be 
accurate to +\2 percent.
    7.1.5 A timing/control device capable of starting and stopping the 
sampler shall be used to obtain a sample collection period of 24 +\1 hr 
(1,440 +\60 min). An elapsed time meter, accurate to within +\15 
minutes, shall be used to measure sampling time. This meter is optional 
for samplers with continuous flow recorders if the sampling time 
measurement obtained by means of the recorder meets the +\15 minute 
accuracy specification.
    7.1.6 The sampler shall have an associated operation or instruction 
manual as required by part 53 of this chapter which includes detailed 
instructions on the calibration, operation, and maintenance of the 
sampler.
    7.2 Filters.
    7.2.1 Filter Medium. No commercially available filter medium is 
ideal in all respects for all samplers. The user's goals in sampling 
determine the relative importance of various filter characteristics, 
e.g., cost, ease of handling, physical and chemical characteristics, 
etc., and, consequently, determine the choice among acceptable filters. 
Furthermore, certain types of filters may not be suitable for use with 
some samplers, particularly under heavy loading conditions (high mass 
concentrations), because of high or rapid increase in the filter flow 
resistance that would exceed the capability of the sampler's flow 
control device. However, samplers equipped with automatic filter-
changing

[[Page 119]]

mechanisms may allow use of these types of filters. The specifications 
given below are minimum requirements to ensure acceptability of the 
filter medium for measurement of PM<INF>10</INF> mass concentrations. 
Other filter evaluation criteria should be considered to meet individual 
sampling and analysis objectives.
    7.2.2 Collection Efficiency. </=99 percent, as measured by the DOP 
test (ASTM-2986) with 0.3 <greek mu<ls-thn-eq>m particles at the 
sampler's operating face velocity.
    7.2.3 Integrity. +\5 <greek mu<ls-thn-eq>g/m\3\ (assuming sampler's 
nominal 24-hour air sample volume). Integrity is measured as the 
PM<INF>10</INF> concentration equivalent corresponding to the average 
difference between the initial and the final weights of a random sample 
of test filters that are weighed and handled under actual or simulated 
sampling conditions, but have no air sample passed through them, i.e., 
filter blanks. As a minimum, the test procedure must include initial 
equilibration and weighing, installation on an inoperative sampler, 
removal from the sampler, and final equilibration and weighing.
    7.2.4 Alkalinity. <25 microequivalents/gram of filter, as measured 
by the procedure given in reference 13 of section 12.0 of this appendix 
following at least two months storage in a clean environment (free from 
contamination by acidic gases) at room temperature and humidity.
    7.3 Flow Rate Transfer Standard. The flow rate transfer standard 
must be suitable for the sampler's operating flow rate and must be 
calibrated against a primary flow or volume standard that is traceable 
to the National Institute of Standard and Technology (NIST). The flow 
rate transfer standard must be capable of measuring the sampler's 
operating flow rate with an accuracy of +\2 percent.
    7.4 Filter Conditioning Environment.
    7.4.1 Temperature range. 15 to 30 C.
    7.4.2 Temperature control. +\3 C.
    7.4.3 Humidity range. 20% to 45% RH.
    7.4.4 Humidity control. +\5% RH.
    7.5 Analytical Balance. The analytical balance must be suitable for 
weighing the type and size of filters required by the sampler. The range 
and sensitivity required will depend on the filter tare weights and mass 
loadings. Typically, an analytical balance with a sensitivity of 0.1 mg 
is required for high volume samplers (flow rates <ls-thn-eq>0.5 m\3\/
min). Lower volume samplers (flow rates <0.5 m\3\/min) will require a 
more sensitive balance.
    8.0 Calibration.
    8.1 General Requirements.
    8.1.1 Calibration of the sampler's flow measurement device is 
required to establish traceability of subsequent flow measurements to a 
primary standard. A flow rate transfer standard calibrated against a 
primary flow or volume standard shall be used to calibrate or verify the 
accuracy of the sampler's flow measurement device.
    8.1.2 Particle size discrimination by inertial separation requires 
that specific air velocities be maintained in the sampler's air inlet 
system. Therefore, the flow rate through the sampler's inlet must be 
maintained throughout the sampling period within the design flow rate 
range specified by the manufacturer. Design flow rates are specified as 
actual volumetric flow rates, measured at existing conditions of 
temperature and pressure (Q<INF>a</INF>).
    8.2 Flow Rate Calibration Procedure.
    8.2.1 PM<INF>10</INF> samplers employ various types of flow control 
and flow measurement devices. The specific procedure used for flow rate 
calibration or verification will vary depending on the type of flow 
controller and flow rate indicator employed. Calibration is in terms of 
actual volumetric flow rates (Q<INF>a</INF>) to meet the requirements of 
section 8.1 of this appendix. The general procedure given here serves to 
illustrate the steps involved in the calibration. Consult the sampler 
manufacturer's instruction manual and reference 2 of section 12.0 of 
this appendix for specific guidance on calibration. Reference 14 of 
section 12.0 of this appendix provides additional information on various 
other measures of flow rate and their interrelationships.
    8.2.2 Calibrate the flow rate transfer standard against a primary 
flow or volume standard traceable to NIST. Establish a calibration 
relationship, e.g., an equation or family of curves, such that 
traceability to the primary standard is accurate to within 2 percent 
over the expected range of ambient conditions, i.e., temperatures and 
pressures, under which the transfer standard will be used. Recalibrate 
the transfer standard periodically.
    8.2.3 Following the sampler manufacturer's instruction manual, 
remove the sampler inlet and connect the flow rate transfer standard to 
the sampler such that the transfer standard accurately measures the 
sampler's flow rate. Make sure there are no leaks between the transfer 
standard and the sampler.
    8.2.4 Choose a minimum of three flow rates (actual m\3\/min), spaced 
over the acceptable flow rate range specified for the inlet, under 
section 7.1.2 of the appendix, that can be obtained by suitable 
adjustment of the sampler flow rate. In accordance with the sampler 
manufacturer's instruction manual, obtain or verify the calibration 
relationship between the flow rate (actual m\3\/min) as indicated by the 
transfer standard and the sampler's flow indicator response. Record the 
ambient temperature and barometric pressure. Temperature and pressure 
corrections to subsequent flow indicator readings may be required for 
certain types of flow measurement devices. When such corrections are 
necessary, correction on an individual or

[[Page 120]]

daily basis is preferable. However, seasonal average temperature and 
average barometric pressure for the sampling site may be incorporated 
into the sampler calibration to avoid daily corrections. Consult the 
sampler manufacturer's instruction manual and reference 2 in section 
12.0 of this appendix for additional guidance.
    8.2.5 Following calibration, verify that the sampler is operating at 
its design flow rate (actual m\3\/min) with a clean filter in place.
    8.2.6 Replace the sampler inlet.
    9.0 Procedure.
    9.1 The sampler shall be operated in accordance with the specific 
guidance provided in the sampler manufacturer's instruction manual and 
in reference 2 in section 12.0 of this appendix. The general procedure 
given here assumes that the sampler's flow rate calibration is based on 
flow rates at ambient conditions (Q<INF>a</INF>) and serves to 
illustrate the steps involved in the operation of a PM<INF>10</INF> 
sampler.
    9.2 Inspect each filter for pinholes, particles, and other 
imperfections. Establish a filter information record and assign an 
identification number to each filter.
    9.3 Equilibrate each filter in the conditioning environment (see 
7.4) for at least 24 hours.
    9.4 Following equilibration, weigh each filter and record the 
presampling weight with the filter identification number.
    9.5 Install a preweighed filter in the sampler following the 
instructions provided in the sampler manufacturer's instruction manual.
    9.6 (a) Turn on the sampler and allow it to establish run-
temperature conditions. Record the flow indicator reading and, if 
needed, the ambient temperature and barometric pressure. Determine the 
sampler flow rate (actual m\3\/min) in accordance with the instructions 
provided in the sampler manufacturer's instruction manual.
    (b) Note: No onsite temperature or pressure measurements are 
necessary if the sampler's flow indicator does not require temperature 
or pressure corrections or if seasonal average temperature and average 
barometric pressure for the sampling site are incorporated into the 
sampler calibration, under section 8.2.4 of this appendix. If individual 
or daily temperature and pressure corrections are required, ambient 
temperature and barometric pressure can be obtained by on-site 
measurements or from a nearby weather station. Barometric pressure 
readings obtained from airports must be station pressure, not corrected 
to sea level, and may need to be corrected for differences in elevation 
between the sampling site and the airport.
    9.7 If the flow rate is outside the acceptable range specified by 
the manufacturer, check for leaks, and if necessary, adjust the flow 
rate to the specified setpoint. Stop the sampler.
    9.8 Set the timer to start and stop the sampler at appropriate 
times. Set the elapsed time meter to zero or record the initial meter 
reading.
    9.9 Record the sample information (site location or identification 
number, sample date, filter identification number, and sampler model and 
serial number).
    9.10 Sample for 24+\1 hours.
    9.11 Determine and record the average flow rate (Q<INF>a</INF>) in 
actual m\3\/min for the sampling period in accordance with the 
instructions provided in the sampler manufacturer's instruction manual. 
Record the elapsed time meter final reading and, if needed, the average 
ambient temperature and barometric pressure for the sampling period, in 
note following section 9.6 of this appendix.
    9.12 Carefully remove the filter from the sampler, following the 
sampler manufacturer's instruction manual. Touch only the outer edges of 
the filter.
    9.13 Place the filter in a protective holder or container, e.g., 
petri dish, glassine envelope, or manila folder.
    9.14 Record any factors such as meteorological conditions, 
construction activity, fires or dust storms, etc., that might be 
pertinent to the measurement on the filter information record.
    9.15 Transport the exposed sample filter to the filter conditioning 
environment as soon as possible for equilibration and subsequent 
weighing.
    9.16 Equilibrate the exposed filter in the conditioning environment 
for at least 24 hours under the same temperature and humidity conditions 
used for presampling filter equilibration (see section 9.3 of this 
appendix).
    9.17 Immediately after equilibration, reweigh the filter and record 
the postsampling weight with the filter identification number.
    10.0 Sampler Maintenance.
    10.1 The PM<INF>10</INF> sampler shall be maintained in strict 
accordance with the maintenance procedures specified in the sampler 
manufacturer's instruction manual.
    11.0 Calculations.
    11.1 Calculate the total volume of air sampled as:

V = Q<INF>a</INF>t

where:

V = total air sampled, at ambient temperature and pressure,m\3\;
Q<INF>a</INF> = average sample flow rate at ambient temperature and 
pressure, m\3\/min; and
t = sampling time, min.
    11.2 (a) Calculate the PM<INF>10</INF> concentration as:

PM<INF>10</INF> = (W<INF>f</INF>-W<INF>i</INF>)x10\6\/V

where:

[[Page 121]]

PM<INF>10</INF> = mass concentration of PM<INF>10</INF>, <greek 
mu<ls-thn-eq>g/m\3\;
W<INF>f</INF>, W<INF>i</INF> = final and initial weights of filter 
collecting PM<INF>1O</INF> particles, g; and
10\6\ = conversion of g to <greek mu<ls-thn-eq>g.

    (b) Note: If more than one size fraction in the PM<INF>10</INF> size 
range is collected by the sampler, the sum of the net weight gain by 
each collection filter [<greek sigma<ls-thn-eq>(W<INF>f</INF>-
W<INF>i</INF>)] is used to calculate the PM<INF>10</INF> mass 
concentration.
    12.0 References.
    1. Quality Assurance Handbook for Air Pollution Measurement Systems, 
Volume I, Principles. EPA-600/9-76-005, March 1976. Available from CERI, 
ORD Publications, U.S. Environmental Protection Agency, 26 West St. 
Clair Street, Cincinnati, OH 45268.
    2. Quality Assurance Handbook for Air Pollution Measurement Systems, 
Volume II, Ambient Air Specific Methods. EPA-600/4-77-027a, May 1977. 
Available from CERI, ORD Publications, U.S. Environmental Protection 
Agency, 26 West St. Clair Street, Cincinnati, OH 45268.
    3. Clement, R.E., and F.W. Karasek. Sample Composition Changes in 
Sampling and Analysis of Organic Compounds in Aerosols. Int. J. Environ. 
Analyt. Chem., 7:109, 1979.
    4. Lee, R.E., Jr., and J. Wagman. A Sampling Anomaly in the 
Determination of Atmospheric Sulfate Concentration. Amer. Ind. Hyg. 
Assoc. J., 27:266, 1966.
    5. Appel, B.R., S.M. Wall, Y. Tokiwa, and M. Haik. Interference 
Effects in Sampling Particulate Nitrate in Ambient Air. Atmos. Environ., 
13:319, 1979.
    6. Coutant, R.W. Effect of Environmental Variables on Collection of 
Atmospheric Sulfate. Environ. Sci. Technol., 11:873, 1977.Spicer, C.W., 
and P. Schumacher. Interference in Sampling Atmospheric Particulate 
Nitrate. Atmos. Environ., 11:873, 1977.
    8. Appel, B.R., Y. Tokiwa, and M. Haik. Sampling of Nitrates in 
Ambient Air. Atmos. Environ., 15:283, 1981.
    9. Spicer, C.W., and P.M. Schumacher. Particulate Nitrate: 
Laboratory and Field Studies of Major Sampling Interferences. Atmos. 
Environ., 13:543, 1979.
    10. Appel, B.R. Letter to Larry Purdue, U.S. EPA, Environmental 
Monitoring and Support Laboratory. March 18, 1982, Docket No. A-82-37, 
II-I-1.
    11. Pierson, W.R., W.W. Brachaczek, T.J. Korniski, T.J. Truex, and 
J.W. Butler. Artifact Formation of Sulfate, Nitrate, and Hydrogen Ion on 
Backup Filters: Allegheny Mountain Experiment. J. Air Pollut. Control 
Assoc., 30:30, 1980.
    12. Dunwoody, C.L. Rapid Nitrate Loss From PM<INF>10</INF> Filters. 
J. Air Pollut. Control Assoc., 36:817, 1986.
    13. Harrell, R.M. Measuring the Alkalinity of Hi-Vol Air Filters. 
EMSL/RTP-SOP-QAD-534, October 1985. Available from the U.S. 
Environmental Protection Agency, EMSL/QAD, Research Triangle Park, NC 
27711.
    14. Smith, F., P.S. Wohlschlegel, R.S.C. Rogers, and D.J. Mulligan. 
Investigation of Flow Rate Calibration Procedures Associated With the 
High Volume Method for Determination of Suspended Particulates. EPA-600/
4-78-047, U.S. Environmental Protection Agency, Research Triangle Park, 
NC 27711, 1978.

[62 FR 38753, July 18, 1997]

   Appendix N to Part 50--Interpretation of the National Ambient Air 
                Quality Standards for Particulate Matter

    1.0 General.
    (a) This appendix explains the data handling conventions and 
computations necessary for determining when the annual and 24-hour 
primary and secondary national ambient air quality standards for PM 
specified in Sec. 50.7 of this chapter are met. Particulate matter is 
measured in the ambient air as PM<INF>10</INF> and PM<INF>2.5</INF> 
(particles with an aerodynamic diameter less than or equal to a nominal 
10 and 2.5 micrometers, respectively) by a reference method based on 
appendix M of this part for PM<INF>10</INF> and on appendix L of this 
part for PM<INF>2.5</INF>, as applicable, and designated in accordance 
with part 53 of this chapter, or by an equivalent method designated in 
accordance with part 53 of this chapter. Data handling and computation 
procedures to be used in making comparisons between reported 
PM<INF>10</INF> and PM<INF>2.5</INF> concentrations and the levels of 
the PM standards are specified in the following sections.
    (b) Data resulting from uncontrollable or natural events, for 
example structural fires or high winds, may require special 
consideration. In some cases, it may be appropriate to exclude these 
data because they could result in inappropriate values to compare with 
the levels of the PM standards. In other cases, it may be more 
appropriate to retain the data for comparison with the level of the PM 
standards and then allow the EPA to formulate the appropriate regulatory 
response. Whether to exclude, retain, or make adjustments to the data 
affected by uncontrollable or natural events is subject to the approval 
of the appropriate Regional Administrator.
    (c) The terms used in this appendix are defined as follows:
    Average and mean refer to an arithmetic mean.
    Daily value for PM refers to the 24-hour average concentration of PM 
calculated or measured from midnight to midnight (local time) for 
PM<INF>10</INF> or PM<INF>2.5</INF>.
    Designated monitors are those monitoring sites designated in a State 
PM Monitoring Network Description for spatial averaging in areas opting 
for spatial averaging in accordance with part 58 of this chapter.

[[Page 122]]

    98<SUP>th</SUP> percentile (used for PM<INF>2.5</INF>) means the 
daily value out of a year of monitoring data below which 98 percent of 
all values in the group fall.
    99<SUP>th</SUP> percentile (used for PM<INF>10</INF>) means the 
daily value out of a year of monitoring data below which 99 percent of 
all values in the group fall.
    Year refers to a calendar year.
    (d) Sections 2.1 and 2.5 of this appendix contain data handling 
instructions for the option of using a spatially averaged network of 
monitors for the annual standard. If spatial averaging is not considered 
for an area, then the spatial average is equivalent to the annual 
average of a single site and is treated accordingly in subsequent 
calculations. For example, paragraph (a)(3) of section 2.1 of this 
appendix could be eliminated since the spatial average would be 
equivalent to the annual average.
    2.0 Comparisons with the PM<INF>2.5</INF> Standards.
    2.1 Annual PM<INF>2.5</INF> Standard.
    (a) The annual PM<INF>2.5</INF> standard is met when the 3-year 
average of the spatially averaged annual means is less than or equal to 
15.0 <greek mu<ls-thn-eq>g/m\3\. The 3-year average of the spatially 
averaged annual means is determined by averaging quarterly means at each 
monitor to obtain the annual mean PM<INF>2.5</INF> concentrations at 
each monitor, then averaging across all designated monitors, and finally 
averaging for 3 consecutive years. The steps can be summarized as 
follows:
    (1) Average 24-hour measurements to obtain quarterly means at each 
monitor.
    (2) Average quarterly means to obtain annual means at each monitor.
    (3) Average across designated monitoring sites to obtain an annual 
spatial mean for an area (this can be one site in which case the spatial 
mean is equal to the annual mean).
    (4) Average 3 years of annual spatial means to obtain a 3-year 
average of spatially averaged annual means.
    (b) In the case of spatial averaging, 3 years of spatial averages 
are required to demonstrate that the standard has been met. Designated 
sites with less than 3 years of data shall be included in spatial 
averages for those years that data completeness requirements are met. 
For the annual PM<INF>2.5</INF> standard, a year meets data completeness 
requirements when at least 75 percent of the scheduled sampling days for 
each quarter have valid data. However, years with high concentrations 
and more than a minimal amount of data (at least 11 samples in each 
quarter) shall not be ignored just because they are comprised of 
quarters with less than complete data. Thus, in computing annual 
spatially averaged means, years containing quarters with at least 11 
samples but less than 75 percent data completeness shall be included in 
the computation if the resulting spatially averaged annual mean 
concentration (rounded according to the conventions of section 2.3 of 
this appendix) is greater than the level of the standard.
    (c) Situations may arise in which there are compelling reasons to 
retain years containing quarters which do not meet the data completeness 
requirement of 75 percent or the minimum number of 11 samples. The use 
of less than complete data is subject to the approval of the appropriate 
Regional Administrator.
    (d) The equations for calculating the 3-year average annual mean of 
the PM<INF>2.5</INF> standard are given in section 2.5 of this appendix.
    2.2 24-Hour PM<INF>2.5</INF> Standard.
    (a) The 24-hour PM<INF>2.5</INF> standard is met when the 3-year 
average of the 98<SUP>th</SUP> percentile values at each monitoring site 
is less than or equal to 65 <greek mu<ls-thn-eq>g/m\3\. This comparison 
shall be based on 3 consecutive, complete years of air quality data. A 
year meets data completeness requirements when at least 75 percent of 
the scheduled sampling days for each quarter have valid data. However, 
years with high concentrations shall not be ignored just because they 
are comprised of quarters with less than complete data. Thus, in 
computing the 3-year average 98<SUP>th</SUP> percentile value, years 
containing quarters with less than 75 percent data completeness shall be 
included in the computation if the annual 98<SUP>th</SUP> percentile 
value (rounded according to the conventions of section 2.3 of this 
appendix) is greater than the level of the standard.
    (b) Situations may arise in which there are compelling reasons to 
retain years containing quarters which do not meet the data completeness 
requirement. The use of less than complete data is subject to the 
approval of the appropriate Regional Administrator.
    (c) The equations for calculating the 3-year average of the annual 
98<SUP>th</SUP> percentile values is given in section 2.6 of this 
appendix.
    2.3 Rounding Conventions. For the purposes of comparing calculated 
values to the applicable level of the standard, it is necessary to round 
the final results of the calculations described in sections 2.5 and 2.6 
of this appendix. For the annual PM<INF>2.5</INF> standard, the 3-year 
average of the spatially averaged annual means shall be rounded to the 
nearest 0.1 <greek mu<ls-thn-eq>g/m\3\ (decimals 0.05 and greater are 
rounded up to the next 0.1, and any decimal lower than 0.05 is rounded 
down to the nearest 0.1). For the 24-hour PM<INF>2.5</INF> standard, the 
3-year average of the annual 98<SUP>th</SUP> percentile values shall be 
rounded to the nearest 1 <greek mu<ls-thn-eq>g/m\3\ (decimals 0.5 and 
greater are rounded up to nearest whole number, and any decimal lower 
than 0.5 is rounded down to the nearest whole number).
    2.4 Monitoring Considerations.
    (a) Section 58.13 of this chapter specifies the required minimum 
frequency of sampling

[[Page 123]]

for PM<INF>2.5</INF>. Exceptions to the specified sampling frequencies, 
such as a reduced frequency during a season of expected low 
concentrations, are subject to the approval of the appropriate Regional 
Administrator. Section 58.14 of 40 CFR part 58 and section 2.8 of 
appendix D of 40 CFR part 58, specify which monitors are eligible for 
making comparisons with the PM standards. In determining a spatial mean 
using two or more monitoring sites operating in a given year, the annual 
mean for an individual site may be included in the spatial mean if and 
only if the mean for that site meets the criterion specified in Sec. 2.8 
of appendix D of 40 CFR part 58. In the event data from an otherwise 
eligible site is excluded from being averaged with data from other sites 
on the basis of this criterion, then the 3-year mean from that site 
shall be compared directly to the annual standard.
    (b) For the annual PM<INF>2.5</INF> standard, when designated 
monitors are located at the same site and are reporting PM<INF>2.5</INF> 
values for the same time periods, and when spatial averaging has been 
chosen, their concentrations shall be averaged before an area-wide 
spatial average is calculated. Such monitors will then be considered as 
one monitor.
    2.5 Equations for the Annual PM<INF>2.5</INF> Standard.
    (a) An annual mean value for PM<INF>2.5</INF> is determined by first 
averaging the daily values of a calendar quarter:

                               Equation 1
[GRAPHIC] [TIFF OMITTED] TR18JY97.000

where:

x<INF>q,y,s</INF> = the mean for quarter q of year y for site s;
n<INF>q</INF> = the number of monitored values in the quarter; and
x<INF>i,q,y,s</INF> = the i<SUP>th</SUP> value in quarter q for year y 
for site s.

    (b) The following equation is then to be used for calculation of the 
annual mean:

                               Equation 2
[GRAPHIC] [TIFF OMITTED] TR18JY97.001

where:

x<INF>y,s</INF> = the annual mean concentration for year y (y = 1, 2, or 
3) and for site s; and
x<INF>q,y,s</INF> = the mean for quarter q of year y for site s.

    (c)(1) The spatially averaged annual mean for year y is computed by 
first calculating the annual mean for each site designated to be 
included in a spatial average, x<INF>y,s</INF>, and then computing the 
average of these values across sites:

                               Equation 3
[GRAPHIC] [TIFF OMITTED] TR18JY97.002

where:

x<INF>y</INF> = the spatially averaged mean for year y;
x<INF>y,s</INF> = the annual mean for year y and site s; and
n<INF>s</INF> = the number of sites designated to be averaged.

    (2) In the event that an area designated for spatial averaging has 
two or more sites at the same location producing data for the same time 
periods, the sites are averaged together before using Equation 3 by:

                               Equation 4
[GRAPHIC] [TIFF OMITTED] TR18JY97.003

where:

x<INF>y,s*</INF> = the annual mean for year y for the sites at the same 
location (which will now be considered one site);
n<INF>c</INF> = the number of sites at the same location designated to 
be included in the spatial average; and
x<INF>y,s</INF> = the annual mean for year y and site s.

    (d) The 3-year average of the spatially averaged annual means is 
calculated by using the following equation:

                               Equation 5
[GRAPHIC] [TIFF OMITTED] TR18JY97.004

where:

x = the 3-year average of the spatially averaged annual means; and
x<INF>y</INF> = the spatially averaged annual mean for year y.

Example 1--Area Designated for Spatial Averaging That Meets the Primary 
                    Annual PM<INF>2.5</INF> Standard.

    a. In an area designated for spatial averaging, four designated 
monitors recorded data in at least 1 year of a particular 3-year period. 
Using Equations 1 and 2, the annual means for PM<INF>2.5</INF> at each 
site are calculated for each year. The following table can be created 
from the results. Data completeness percentages for the quarter with the 
fewest number of samples are also shown.

[[Page 124]]

                                                         Table 1--Results from Equations 1 and 2
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                       Site 1        Site 2        Site 3        Site 4     Spatial mean
--------------------------------------------------------------------------------------------------------------------------------------------------------
Year 1.........................................  Annual mean (<greek mu<ls-thn-             12.7  ............  ............  ............         12.7
                                                  eq>g/m\3\).
                                                 % data completeness..............          80             0             0             0    ............
Year 2.........................................  Annual mean (<greek mu<ls-thn-             12.6          17.5          15.2  ............         15.05
                                                  eq>g/m\3\).
                                                 % data completeness..............          90            63            38             0    ............
Year 3.........................................  Annual mean (<greek mu<ls-thn-             12.5          18.5          14.1          16.9         15.50
                                                  eq>g/m\3\).
                                                 % data completeness..............          90            80            85            50    ............
3-year mean....................................  .................................  ............  ............  ............  ............         14.42
--------------------------------------------------------------------------------------------------------------------------------------------------------

    b. The data from these sites are averaged in the order described in 
section 2.1 of this appendix. Note that the annual mean from site 
<greek-i>3 in year 2 and the annual mean from site <greek-i>4 in year 3 
do not meet the 75 percent data completeness criteria. Assuming the 38 
percent data completeness represents a quarter with fewer than 11 
samples, site <greek-i>3 in year 2 does not meet the minimum data 
completeness requirement of 11 samples in each quarter. The site is 
therefore excluded from the calculation of the spatial mean for year 2. 
However, since the spatial mean for year 3 is above the level of the 
standard and the minimum data requirement of 11 samples in each quarter 
has been met, the annual mean from site <greek-i>4 in year 3 is included 
in the calculation of the spatial mean for year 3 and in the calculation 
of the 3-year average. The 3-year average is rounded to 14.4 <greek 
mu<ls-thn-eq>g/m\3\, indicating that this area meets the annual 
PM<INF>2.5</INF> standard.

 Example 2--Area With Two Monitors at the Same Location That Meets the 
                Primary Annual PM<INF>2.5</INF> Standard.

    a. In an area designated for spatial averaging, six designated 
monitors, with two monitors at the same location (<greek-i>5 and 
<greek-i>6), recorded data in a particular 3-year period. Using 
Equations 1 and 2, the annual means for PM<INF>2.5</INF> are calculated 
for each year. The following table can be created from the results.

                                                         Table 2--Results From Equations 1 and 2
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                  Average of    Spatial
     Annual mean (<greek mu<ls-thn-eq>g/m\3\)          Site 1       Site 2       Site 3       Site 4       Site 5       Site 6      5 and 6      mean
--------------------------------------------------------------------------------------------------------------------------------------------------------
Year 1............................................         12.9          9.9         12.6         11.1         14.5         14.6       14.55       12.21
Year 2............................................         14.5         13.3         12.2         10.9         16.1         16.0       16.05       13.39
Year 3............................................         14.4         12.4         11.5          9.7         12.3         12.1       12.20       12.04
3-Year mean.......................................  ...........  ...........  ...........  ...........  ...........  ...........  ..........       12.55
--------------------------------------------------------------------------------------------------------------------------------------------------------

    b. The annual means for sites <greek-i>5 and <greek-i>6 are averaged 
together using Equation 4 before the spatial average is calculated using 
Equation 3 since they are in the same location. The 3-year mean is 
rounded to 12.6 <greek mu<ls-thn-eq>g/m\3\, indicating that this area 
meets the annual PM<INF>2.5</INF> standard.

  Example 3--Area With a Single Monitor That Meets the Primary Annual 
                       PM<INF>2.5</INF> Standard.

    a. Given data from a single monitor in an area, the calculations are 
as follows. Using Equations 1 and 2, the annual means for 
PM<INF>2.5</INF> are calculated for each year. If the annual means are 
10.28, 17.38, and 12.25 <greek mu<ls-thn-eq>g/m\3\, then the 3-year mean 
is:
[GRAPHIC] [TIFF OMITTED] TR18JY97.005

    b. This value is rounded to 13.3, indicating that this area meets 
the annual PM<INF>2.5</INF> standard.
    2.6 Equations for the 24-Hour PM<INF>2.5</INF> Standard.
    (a) When the data for a particular site and year meet the data 
completeness requirements in section 2.2 of this appendix, calculation 
of the 98<SUP>th</SUP> percentile is accomplished by the following 
steps. All the daily values from a particular site and year comprise a 
series of values (x<INF>1</INF>, x<INF>2</INF>, x<INF>3</INF>, ..., 
x<INF>n</INF>), that can be sorted into a series where each number is 
equal to or larger than the preceding number (x<INF>[1]</INF>, 
x<INF>[2]</INF>, x<INF>[3]</INF>, ..., x<INF>[n]</INF>). In this case, 
x<INF>[1]</INF> is the smallest number and x<INF>[n]</INF> is the 
largest value. The 98<SUP>th</SUP> percentile is found from the

[[Page 125]]

sorted series of daily values which is ordered from the lowest to the 
highest number. Compute (0.98) x (n) as the number ``i.d'', where ``i'' 
is the integer part of the result and ``d'' is the decimal part of the 
result. The 98<SUP>th</SUP> percentile value for year y, 
P<INF>0.98, y</INF>, is given by Equation 6:

                               Equation 6
[GRAPHIC] [TIFF OMITTED] TR18JY97.006

where:

P<INF>0.98,y</INF> = 98<SUP>th</SUP> percentile for year y;
x<INF>[i=1]</INF> = the (i=1)<SUP>th</SUP> number in the ordered series 
of numbers; and
i = the integer part of the product of 0.98 and n.

    (b) The 3-year average 98<SUP>th</SUP> percentile is then calculated 
by averaging the annual 98<SUP>th</SUP> percentiles:

                               Equation 7
[GRAPHIC] [TIFF OMITTED] TR18JY97.007

    (c) The 3-year average 98<SUP>th</SUP> percentile is rounded 
according to the conventions in section 2.3 of this appendix before a 
comparison with the standard is made.

 Example 4--Ambient Monitoring Site With Every-Day Sampling That Meets 
             the Primary 24-Hour PM<INF>2.5</INF> Standard.

    a. In each year of a particular 3 year period, varying numbers of 
daily PM<INF>2.5</INF> values (e.g., 281, 304, and 296) out of a 
possible 365 values were recorded at a particular site with the 
following ranked values (in <greek mu<ls-thn-eq>g/m\3\):

                                  Table 3--Ordered Monitoring Data For 3 Years
----------------------------------------------------------------------------------------------------------------
               Year 1                                Year 2                                Year 3
----------------------------------------------------------------------------------------------------------------
      j rank            X<INF>j</INF> value            j rank            X<INF>j</INF> value            j rank            X<INF>j</INF> value
----------------------------------------------------------------------------------------------------------------
           275               57.9                296               54.3                290               66.0
           276               59.0                297               57.1                291               68.4
           277               62.2                298               63.0                292               69.8
----------------------------------------------------------------------------------------------------------------

    b. Using Equation 6, the 98<SUP>th</SUP> percentile values for each 
year are calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR18JY97.008

[GRAPHIC] [TIFF OMITTED] TR18JY97.009

[GRAPHIC] [TIFF OMITTED] TR18JY97.010

    c.1. Using Equation 7, the 3-year average 98<SUP>th</SUP> percentile 
is calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR18JY97.011

    2. Therefore, this site meets the 24-hour PM<INF>2.5</INF> standard.
    3.0 Comparisons with the PM<INF>10</INF> Standards.
    3.1 Annual PM<INF>10</INF> Standard.
    (a) The annual PM<INF>10</INF> standard is met when the 3-year 
average of the annual mean PM<INF>10</INF> concentrations at each 
monitoring site is less than or equal to 50 <greek mu<ls-thn-eq>g/m\3\. 
The 3-year average of the annual means is determined by averaging 
quarterly means to obtain annual mean PM<INF>10</INF> concentrations for 
3 consecutive, complete years at each monitoring site. The steps can be 
summarized as follows:
    (1) Average 24-hour measurements to obtain a quarterly mean.

[[Page 126]]

    (2) Average quarterly means to obtain an annual mean.
    (3) Average annual means to obtain a 3-year mean.
    (b) For the annual PM<INF>10</INF> standard, a year meets data 
completeness requirements when at least 75 percent of the scheduled 
sampling days for each quarter have valid data. However, years with high 
concentrations and more than a minimal amount of data (at least 11 
samples in each quarter) shall not be ignored just because they are 
comprised of quarters with less than complete data. Thus, in computing 
the 3-year average annual mean concentration, years containing quarters 
with at least 11 samples but less than 75 percent data completeness 
shall be included in the computation if the annual mean concentration 
(rounded according to the conventions of section 2.3 of this appendix) 
is greater than the level of the standard.
    (c) Situations may arise in which there are compelling reasons to 
retain years containing quarters which do not meet the data completeness 
requirement of 75 percent or the minimum number of 11 samples. The use 
of less than complete data is subject to the approval of the appropriate 
Regional Administrator.
    (d) The equations for calculating the 3-year average annual mean of 
the PM<INF>10</INF> standard are given in section 3.5 of this appendix.
    3.2 24-Hour PM<INF>10</INF> Standard.
    (a) The 24-hour PM<INF>10</INF> standard is met when the 3-year 
average of the annual 99<SUP>th</SUP> percentile values at each 
monitoring site is less than or equal to 150 <greek mu<ls-thn-eq>g/m\3\. 
This comparison shall be based on 3 consecutive, complete years of air 
quality data. A year meets data completeness requirements when at least 
75 percent of the scheduled sampling days for each quarter have valid 
data. However, years with high concentrations shall not be ignored just 
because they are comprised of quarters with less than complete data. 
Thus, in computing the 3-year average of the annual 99<SUP>th</SUP> 
percentile values, years containing quarters with less than 75 percent 
data completeness shall be included in the computation if the annual 
99<SUP>th</SUP> percentile value (rounded according to the conventions 
of section 2.3 of this appendix) is greater than the level of the 
standard.
    (b) Situations may arise in which there are compelling reasons to 
retain years containing quarters which do not meet the data completeness 
requirement. The use of less than complete data is subject to the 
approval of the appropriate Regional Administrator.
    (c) The equation for calculating the 3-year average of the annual 
99<SUP>th</SUP> percentile values is given in section 2.6 of this 
appendix.
    3.3 Rounding Conventions. For the annual PM<INF>10</INF> standard, 
the 3-year average of the annual PM<INF>10</INF> means shall be rounded 
to the nearest 1 <greek mu<ls-thn-eq>g/m\3\ (decimals 0.5 and greater 
are rounded up to the next whole number, and any decimal less than 0.5 
is rounded down to the nearest whole number). For the 24-hour 
PM<INF>10</INF> standard, the 3-year average of the annual 
99<SUP>th</SUP> percentile values of PM<INF>10</INF> shall be rounded to 
the nearest 10 <greek mu<ls-thn-eq>g/m\3\ (155 <greek mu<ls-thn-eq>g/
m\3\ and greater would be rounded to 160 <greek mu<ls-thn-eq>g/m\3\ and 
154 <greek mu<ls-thn-eq>g/m\3\ and less would be rounded to 150 <greek 
mu<ls-thn-eq>g/m\3\).
    3.4 Monitoring Considerations. Section 58.13 of this chapter 
specifies the required minimum frequency of sampling for 
PM<INF>10</INF>. Exceptions to the specified sampling frequencies, such 
as a reduced frequency during a season of expected low concentrations, 
are subject to the approval of the appropriate Regional Administrator. 
For making comparisons with the PM<INF>10</INF> NAAQS, all sites meeting 
applicable requirements in part 58 of this chapter would be used.
    3.5 Equations for the Annual PM<INF>10</INF> Standard.
    (a) An annual arithmetic mean value for PM<INF>10</INF> is 
determined by first averaging the 24-hour values of a calendar quarter 
using the following equation:

                               Equation 8
[GRAPHIC] [TIFF OMITTED] TR18JY97.012

where:

x<INF>q,y</INF> = the mean for quarter q of year y;
n<INF>q</INF> = the number of monitored values in the quarter; and
x<INF>i,q,y</INF> = the i<SUP>th</SUP> value in quarter q for year y.

    (b) The following equation is then to be used for calculation of the 
annual mean:

                               Equation 9
[GRAPHIC] [TIFF OMITTED] TR18JY97.013

where:

x<INF>y</INF> = the annual mean concentration for year y, (y=1, 2, or 
3); and
x<INF>q,y</INF> = the mean for a quarter q of year y.

    (c) The 3-year average of the annual means is calculated by using 
the following equation:

                               Equation 10
[GRAPHIC] [TIFF OMITTED] TR18JY97.014

where:

x = the 3-year average of the annual means; and

x<INF>y</INF> = the annual mean for calendar year y.

[[Page 127]]

    Example 5--Ambient Monitoring Site That Does Not Meet the Annual 
                        PM<INF>10</INF> Standard.

    a. Given data from a PM<INF>10</INF> monitor and using Equations 8 
and 9, the annual means for PM<INF>10</INF> are calculated for each 
year. If the annual means are 52.42, 82.17, and 63.23 <greek 
mu<ls-thn-eq>g/m\3\, then the 3-year average annual mean is:
[GRAPHIC] [TIFF OMITTED] TR18JY97.015

    b. Therefore, this site does not meet the annual PM<INF>10</INF> 
standard.
    3.6 Equation for the 24-Hour PM<INF>10</INF> Standard.
    (a) When the data for a particular site and year meet the data 
completeness requirements in section 3.2 of this appendix, calculation 
of the 99<SUP>th</SUP> percentile is accomplished by the following 
steps. All the daily values from a particular site and year comprise a 
series of values (x<INF>1</INF>, x<INF>2</INF>, x<INF>3</INF>, ..., 
x<INF>n</INF>) that can be sorted into a series where each number is 
equal to or larger than the preceding number (x<INF>[1]</INF>, 
x<INF>[2]</INF>, x<INF>[3]</INF>, ..., x<INF>[n]</INF>). In this case, 
x<INF>[1]</INF> is the smallest number and x[n] is the largest value. 
The 99<SUP>th</SUP> percentile is found from the sorted series of daily 
values which is ordered from the lowest to the highest number. Compute 
(0.99) x (n) as the number ``i.d'', where ``i'' is the integer part of 
the result and ``d'' is the decimal part of the result. The 
99<SUP>th</SUP> percentile value for year y, P<INF>0.99,y</INF>, is 
given by Equation 11:

                               Equation 11
[GRAPHIC] [TIFF OMITTED] TR18JY97.016

where:

P<INF>0.99,y</INF> = the 99<SUP>th</SUP> percentile for year y;

x<INF>[i=1]</INF> = the (i=1)<SUP>th</SUP> number in the ordered series 
of numbers; and

i = the integer part of the product of 0.99 and n.

    (b) The 3-year average 99<SUP>th</SUP> percentile value is then 
calculated by averaging the annual 99<SUP>th</SUP> percentiles:

                               Equation 12
[GRAPHIC] [TIFF OMITTED] TR18JY97.017

    (c) The 3-year average 99<SUP>th</SUP> percentile is rounded 
according to the conventions in section 3.3 of this appendix before a 
comparison with the standard is made.

 Example 6--Ambient Monitoring Site With Sampling Every Sixth Day That 
           Meets the Primary 24-Hour PM<INF>10</INF> Standard.

    a. In each year of a particular 3 year period, varying numbers of 
PM<INF>10</INF> daily values (e.g., 110, 98, and 100) out of a possible 
121 daily values were recorded at a particular site with the following 
ranked values (in <greek mu<ls-thn-eq>g/m\3\):

                                  Table 4--Ordered Monitoring Data For 3 Years
----------------------------------------------------------------------------------------------------------------
               Year 1                                Year 2                                Year 3
----------------------------------------------------------------------------------------------------------------
      j rank            X<INF>j</INF> value            j rank            X<INF>j</INF> value            j rank            X<INF>j</INF> value
----------------------------------------------------------------------------------------------------------------
           108                120                 96                143                 98                140
           109                128                 97                148                 99                144
           110                130                 98                150                100                147
----------------------------------------------------------------------------------------------------------------

    b. Using Equation 11, the 99<SUP>th</SUP> percentile values for each 
year are calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR18JY97.018

[GRAPHIC] [TIFF OMITTED] TR18JY97.019

[[Page 128]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.020

    c. 1. Using Equation 12, the 3-year average 99<SUP>th</SUP> 
percentile is calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR18JY97.021

    2. Therefore, this site meets the 24-hour PM<INF>10</INF> standard.

[62 FR 38755, July 18, 1997]