RULES AND REGULATIONS

number of days with maximum hourly aver- age 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 exceed- ances relate to accounting for incomplete

sampling. In genera], the average number of

exceedances per calendar year musthe 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 ayerage is less

than or equal to 1.

2. Interpretation of Expected Exceedances

The ozone- standard states that the ex- pected number of exceedances per year

must be less than or equal to 1. The statistlk

cal 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 daysr 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 com- pliance.

3. Estimating the Number of Exceedances

fora 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 exceedancesper 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 measure- ment. 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 maxi- mum value is considered to be valid If 75

percent of the hours from 9:01 am. to 9:00

p.m. (MST) were measured or if the highest

-hour is greater than thp 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 allow- ance 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 missingvalue 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 f 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 thatmay be assumed to be

less than the standard. Then the following

formula shall be used to estimate the ex- pected number of exceedances for the year

e=v+£E(v/n)'(N-n-z)] (1)

(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 standa-d level.

*Indicates multiplication.

This estimated number of exceedances

shall be rounded to one decimal place (fractional parts equal to 0.05 round up).

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) mlsing values for the year but a certain number of

these, namely z. were assumed to be less

than the standard. Therefore, (N-n-z) iming values are considered toinclude 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.

AoHonmrr. Sections 109 and 301 of the

Clean Air Act, as amended (42 U.S.C. 7409.

7601).

(FR Doc. 79-4056 Filed 2-7-79; 8:45 am]

[6560-01-M]

FRL 1018-31

PART 50-NATIONAL PRIMARY AND

SECONDARY AMBIENT AIR QUALITY STANDARDS

Calibration of Ozone Reference

Methods

AGENCY: U.S. Environmental Protection Agency.

ACTION: Final rule.

SUMMARY: Appendix D to 40 CFR

Part 50 prescribes a measurement

principle upon which reference methods for the measurement of ozoneO In

*The term "ozone" Is used herein to be

consistent with another EPA action in this

8221

the atmosphere must be based. This

appendix also specifies a procedure to

be used for calibrating those ozone reference methods. EPA has evidence

that another calibration procedure for ozone reference methods is significantly more accurate and less variable

than the procedure currently specified

in Appendix D. Accordingly, EPA is

amending 40 CFR Part 50, Appendix

D, to replace (supersede) the current

calibration procedure with a superior

calibration procedure based on ultraviolet photometry.

EFFECTIVE DATE: This action is effective immediately upon publication

because the revised standard to which

It applies Is immediately effective.

FOR FURTHMR INFORMATION

CONTAM.

Mr. Larry J. Purdue, Telephone 919-

541-2665 (FTS: 629-2665).

ADDRESS: Department E (MD-77),

Environmental Monitoring 'and Support Laboratory, U.S. Environmental

Protection Agency, Research Triangle

Park, NC 27711.

SUPPLEMENTARY INFORMATION:

BACKGROUND

Part 50 of Title 40, Chapter I of the

Code of Federal Regulations specifies

the National Ambient Air Quality

Standards for several air pollutants including ozone. Appendixes to Part 50

provide information concerning the

reference methods which are used to measure those pollutants. In particular, Appendix D to Part 50 describes a measurement principle upon which ozone reference methods must be/

based, and specifies a calibration procedure to be used for calibrating such

methods. Previously, the calibration

procedure specified by Appendix D was based on assay of ozone with 1%

neutral buffered potassium iodide

(NBKI) and was known as the "NBKI

procedure."

On June 22, 1978, EPA indicated its

conclusion that another calibration

procedure was clearly superior to the

NBKI procedure, and accordingly EPA

proposed an amendment to Appendix

D to replace the NBKI procedure with

the new procedure, based on ultraviolet (UV) photometry (43 FR 26971-

26984). The rationale for the proposed

amendment was discussed In -the preamble to that proposal. Interested per- sons and organizations were afforded

En opportunity to comment on all as- pects of the proposed changes. The

amendment, revised slightly after con- sideration of the public comments, is

being promulgated today in conjuncIssue of the FERAI REGis substituting

"ozone" for "photochemical oxidants cor- rected for Interferences due to nitrogen oxides and sulfur dioxide," which was formerly used in Part 50.

FEDERAL REGISTER, VOL 44, NO. 28--THURSDAY, FEBRUARY 8, 1979

HeinOnline -- 44 Fed. Reg. 8221 1979
RULES AND REGULATIONS

tion with changes in the ambient air

quality standards for photochemical

oxidants (ozone) appearing elsewhere

in this issue of the FEDERAL REGISTER.

NATURE OF CHANGES

The amendment makes three salient

changes to the previous requirements

for calibration of ozone reference

methods. These are as follows:

(1) The NBKI calibration procedure

is superseded by a procedure based on UV photometry for the calibration of

reference methods for ozone. Since no National Bureau of Standards (NBS).

Standard Reference Material is available for ozone, ozone standard concen- trations established via the UV procedure are tantamount to priniary ozone standards, and the UV procedure itself

is thus referred to as a "UV standard"

for ozone.

(2) Independent use of a manual KI

procedure known as the "BAKI procedure" in lieu of the UV procedure is allowed for 18 months after tht effective date of the amendment, with the

recommendation that the BAKI technique be related to a UV standard

whenever possible.

(3) The use of alternative procedures as transfer standards is specifically allowed if they meet certain transfer

standard performance guidelines set

forth by EPA. A transfer standard is

any device or procedure which can be

referenced to a UV ozone standard and

then used at another location to reproduce ozone standards. A practical

transfer standard offers some important advantages-such as lower cost,

ruggedness, easier operation, or con- venience-over direct use of the UV

procedure.

NEW UV CALIBRATION PROdEDURE

The new UV calibration procedure is

quite simple. After generating a stable, ozone concentration with an ozone

generator, the operator assays it by

passing all or a portion of the gas flow

through the cell of a UV photometer.

The photometer readings are then

used in a formula ,to calculate the ozone concentration,' which as noted

earlier, is effectively a primary ozone standard. Most commercially available

photometers do the photometric calculations automatically, and some may

also make temperature and pressure,

corrections automatically. The primary burden on the operator is to insure

(1) that the photometer is operating

correctly, (2) that the apparatus is set

up properly and is clean and leak-free,

and (3) that the calculations are com- plete and accurate. While none of

these is particularly difficult, EPA has

prepared a Technical Assistance Document which explains these tasks and

provides other detailed information

about the procedure. This document,

which is still in draft form to allow

further incorporation of user's com- ments, is available from the address

specified at the beginning Of this preamble.

The photometer is obviously of critical-importance to the procedure and

must have a precision within 0'005

"ppm or 3% of the concentration,

whichever is greater. While a calibration *photometer can be assembled

from laboratory components, EPA recommends the purchase of a commerical photometer which is either designed specifically for this calibration

procedure, or which ,can be readily

adapted to it. EPA is presently aware of 2 such commercial photometers

(available from Dasibi Environmental

Corp., Glendale, California,- and Sci- ence Applications, Inc., La' Jolla, California) and expects others will become

available in the future.

UV photometers of the type used in

ambient ozone analyzers are likely to

be suitable as calibration photometers.

Conversion of an ambient UV analyzer

to a calibration photometer is covered

in the Technical Assistance Document

mentioned above. However, it is important to differentiate between the use of a UV photometer as an ambient

analyzer and its use as a calibration

photometer. This distinction is predi- -

cated more on operational differences

thar on any specific physical differ- ences. The new calibration procedure

requires that a photometer used for

calibration must be dedicated exclusively to such use, must be maintained

-under meticulous conditions, and must

be used ,only with clean, calibration

gases. UV analyzers used for ambient

nonitoring should always be calibrated with an independent calibration

photometer or a certified transfer

standard. A.UV analyzer should'not be

considered to be "self-calibrated" even though it contains a UV photometer

which meets the specifications of the

UV calibration procedure.

Nxv BAKI CALIBRATION PROCEDURE

The New BAKI calibration procedure is very similar to the previously

-specified NBKI procedure. Relatively

minor modifications provide somewhat

less variability- than the NBKI proce"

dure. Agencies which are familiar with

the NBKI procedure should have no difficulty switching to the BAKI procedure. Independent use of the BAKI

prodecure is allowed only for direct

calibration of ozone analyzers (not

transfer standards) on a temporary

basis during the 18-month transition

period to permit agencies to adopt the

new, UV calibration procedure. Nevertheless, the BAKI procedure has more variability than, the UV -procedure.

Therefore, EPA would urge agencies

to adopt the UV procedure- as soon as practical. And, when possible, the

BAKI procedure should be related to

the UV procedure to improve the overall accuracy.

Following the 18-month pdrlod, the

BAKI procedure will not be authorized for independent use, but can be

used as a transfer standard. As such, It

must be related to the UV procedure,

and its variability and accuracy must

be monitored and controlled. Thus,

agencies which find the BAKI procedure advantageous could continue to use this procedure as a transfer standard.

TRANsFERn STANIARDS,,

EPA is specifically allowing transfer

standards for calibrating ozone analyzers, and has noted a number' of advantages which can be realized by their use. Transfer standards for ozone Can

include procedural techniques such as BAKI and gas phase titration, as well as devices such as ozone analyzers and

stable ozone generators. EPA recom- mends that agencies consider the use of transfer standards where advantageous. But transfer standards must

meet certain performance specifications, and their performance must be

monitored. EPA has prepared a Technical Assistance Document on "Transfer Standards for Calibration of Ambient Air Monitoring Analyzers for

Ozone," which gives the required performance specifications and general

guidance on the certification and use of any type of transfer standard for ozone. This document is also still in

draft form to allow incorporation of

further user's comments, and a copy

of it may be obtained from the address

given at the beginning of this preamble.

SULVIARY OF COMMENTs RECEIVED AND

CHANGES MADE TO FINAL AMENDMENT

Comments relative to the proposed

amendment (43 FR 26971) were re- ceived from 26 respondents representing EPA Regional Offices. State and

local air pollution control agencies, industrial corporations, and other organizations. Almost all of the respondents e: pressed general support for the

proposed change to the UV photometric calibration procedure. Other com- ments ranged from Issues of basic

policy to technical aspects of the proposed amendment. After consideration

of all the comments, several minor rer visions and improvements were made

to th. proposed amendment, although

the basic principles and objectives

have not been altered. Specific

changes to the proposed amendment are discussed briefly below.

A document containing a summary

of all the comments received, the Identity of the respondents, the resulting

changes made to the amendment, and

the rationale for adoption or rejection

of each comment is available from the

address given at the beginning of this

FEDERAL REGISTER, VOL 44, NO. 28-THURSDAY, FEBRUARY 8, 1979

8222

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RULES AND REGULATIONS

preamble. This documcnt will also be

added to Docket No. OAQPS 78-8,

which is available for public inspection

during normal business hours at the

USEPA, Central Docket Section, Room•

2903, 401 M 'Street, SW., Washington,

D.C. 20460.

Several respondents pointed to the

relatively high cost of implementing

the change in calibration procedures

and suggested that EPA should either

provide the necessary funds to those

agencies with nonattainment and un- classified areas, or make available, in

each EPA Region, a reference photometer that could be used to certify appropriate transfer standards. Other

comments suggested a similar need for

-such reference photometers until such

time that commercial photometers

become more generally available. EPA

agrees with these general comments

and intends to pursue them, but this

requires no actual change to the

amendment as proposed.

Many of the comments indicated a concern for a lack of reliability inpresent commercial UV systems. Some

of these same respondents recom- mended revisions in the UV calibration procedure to incorporate procedures for checking or calibrating the

photometer's wavelength, path length,

and optical density (or _absorbancy).

However, EPA believes- that the reliability of most commercial photometers will be adequate. The photometer specifications require a non-dispersive optical system which is not

likely to experience changes in the wa- velength. Path length is normally

fixed aid should be adequately specified by the photometer manufacturer.

Optical - density checks with neutral

density filters (for example) are not

practical because of the extremely

small optical density range over which

the photometer normally operates.

The only practical way to check the

response of the photometer is with an absorbing gas such as ozone. The linearity test described in Section 5.2.3 serves this purpose.

There was some concern for whether

the absorption coefficient of ozone at

254 nm (given in the procedure as 308±4 atm-1 cm- 1 at 0"C and 760 torr)

might be different 'at different temperatures. Other comments indicated

that the corrections for temperature

and pressure in the UV photometric

assay -procedure were not always clear.

The absorption coefficient of ozone is,

in fact, quite insensitive to temperature between 0 and 40C-aside from

the normal effect of gas density

change with temperature. For photometers used at. temperatures and pres- sures other than 0° and 760 torr, cor- rections are required according to the

p~rfect gas laws. Efforts are being

made to further clarify these correc- tion procedures in the ozone calibration Technical Assistance Document

mentioned earlier.

A series of comments from one respondent recommended revisions to

the proposed procedure to more clearly allow the use of other UV photometer designs and other configurations

of components within the UV calibra.

tion system. It was further pointed out

that, with certain configurations, some of the components shown In the suggested configuration might not be nec- essary, and some of the procedural

steps in the proposed procedure might

not be necessary or even possible. This

respondent questioned whether UV

photometer linearity tests by the user are necessary if the manufacturer of

the photometer has done the tests.

Modification of the commercial photometer might be necessary to carry

out the tests and any resultant leaks

in the system or improper dilution

techniques might confuse the results.

In response to these comments, EPA

has revised Sections 3, 3.2, and 5.3

somewhat to more explicitly allow alternate systems or system configurations and to provide for appropriate

variations in the procedural steps to

accommodate such systems. Also, Section 5.2.3 on linearity has been

-changed to allow acceptance of the

manufacturer's linearity test in lieu of

the user-conducted test if the manu- facturer can show that the linearity error is less than 3%. When the user carries out the test, the error specification remains at 5% to allow for some variation in the necessary flow meas- urements.

There were several comments re- garding the BAKI calibration procedure and Its use for an interim period

of 18 months. One respondent questioned the wisdom of changing from a known procedure (NBKI) to an un- known procedure (BAKI) and then

changing again to UV photometry

within ,8 months. The respondent rec- ommended that EPA allow the continued use of the NBKI procedure on an interim basis until the change to DV

photometry can be Implemented. Another respondent questioned the ne- cessity of allowing the considerably more variable (than UV photometry)

BAKE procedure for the interim

period, and recommended that com- ments from State and local agencies

directly affected should guide EPA in

this area. EPA agrees that the BAKI procedure is more variable than the UV procedure but believes that some transition period is necessary before the UV

procedure is required exclusively.

There were few comments to the con- trary. EPA considered allowing continued use of the NBKI procedure during

the transition period, but the BAKI

procedure is really only a slightly

modified version of the NBKI procedure and is thus very similar. Since

the change from NBKI to BAKI is so easily made, and the performance of

the BAKI procedure is significantly

better than the NBKI procedure, EPA

feels the interim change to BAKI Is

adequately Justified.

A few relatively minor changes were made to the BAKI procedure in SectIons 1, 3.8, 4.4.4, and 4.4.5 where re- spondents suggested a need for clarification or where various improvements

to the method could be realized. For

example, the units given as "eq" in

equation 5a of the' BAKI were changed to "equivalents" in order that

they not be confused with equivalent

weight. Also, the concentration of the

hydrogen peroxide added in Section

3.8 has been increased slightly and the

specification for the resulting absorbance increase has been reduced from

0.010 to 0.008. Furthermore the calibration slope specification in Section

4.4.5 has been changed from

25,800!600 to 26,000±-780.

While several respondents endorsed

the use of transfer standards in general. one respondent questioned the advLsability of allowing the use of transfer standards based on methods known

to be highly variable even under ideal

conditions. EPA still believes that the

variability of such transfer standards

will be adequately controlled by the

qualification and certification requirements on transfer standards described

in the transfer standard Technical Assistance Document mentioned previously. Hence, EPA has made no major

changes to the transfer standard con- cept as originally proposed.

In regard to EPA's statement that no factor is available to "correct" previously collected ozone measurements

to make them comparable to the new UV standard, one respondent thought that EPA should allow individual

states or Regions to make corrections

to their previously obtained ozone air,

quality data If they have consistent

comparative data for the NBKI and

UV photometric calibration techniques. EPA has re-evaluated this position. but as noted below, still discourages such attempted corrections.

EFcT ON NATIONAL AMIE T AIR

QUA Y STANDARD FOR OZONE

Because of the substantial variability of the NBKI procedure and the unpredictable bias results reported by

various investigators, the exact magnitude of any universal bias which may

exist between the NBKI and UV procedures cannot be determined. However, available data suggest that any

such bias probably does not exceed

10% on the average. For this reason. EPA believes that supersession of the

NBKI calibration procedure with the

UV procedure should have no effect on the magnitude of the National AmFEDERAL REGISTER, VOL 44, NO. 28-THURSDAY, FEBRUARY 8, 1979

.8223'

HeinOnline -- 44 Fed. Reg. 8223 1979
8224

blent ,Air Quality Standard for Ozone

(being revised elsewhere in this issue

of the FEDERAL REGisTER). And for the same reason, EPA discourages any attempt to "correct" or "adjust" previously obtained oxidant or ozone measurements to make them "comparable"

to measurements based on the new UV

calibration procedure-even when individual agencies or laboratories try to

determine a more precise, laboratoryspecific bias value.

EFFECT ON CURRENTLY DESIGNATED

REFERENCE AND EQUIVALENT METHODS

- As noted in the June 22 proposal, a change in the calibration procedure

specified in Appendix D of 40 CFR

Part 50 does not affect the design or performance characteristics of existing reference methods for ozone. The

only effect of the change is on the

calibration procedure describedin the

operation manuals associated with the

analyzers. EPA will allow a 6-month

period of time after final promulgation for manufacturers to revise their

manuals, have the revised mbnuals approved by EPA, and distribute revised

manuals (or manual supplements) to

all analyzer owners.

The two equivalent methods for ozone designated to date prescribe the

NBKI calibration procedure. Because

the 13V calibration procedure and the

transfer standard concept are as beneficial to equivalent methods7 as they are for reference methods, EPA will

also request that.the manufacturers of

the two equivalent methods revise

their respective manuals to specify the

UV procedure or certified transfer

standards for calibration. EPA believes

that, under the circumstances, such a modification to equivalent methods

for ozone is desirable and appropriate

and should not jeopardize their designated status. Conversely, failure to

make such a change may be considered by EPA as possible grounds for

cancellation of the equivalent method

designation under 40 CPR 53.11. If all

manufacturers respond promptly to

this request for appropriate manual

changes, there will be no impact

(other than the change in calibration

procedure itself) to owners of designated ozone analyzers.

REviSION ADOPTED

Accordingly, with the final changes as described above, Appendix D of 40

CFR Part 50 is revised as set forth

below.

Dated: January 26. 1979.

SDOUGLAS M. COSTLE,

Administrator.

RULES AND REGULATIONS

Part 50 of Title 40, Code of Federal the photometer and for the temperature

Regulations is amended as follows: and pressure of the sample. 2 Applicability. This procedure is applica- 1. Appenidix D is revised to read as ble to the calibration of ambient air 0. ann- follows: D-MEAsM Em P lyzers, either directly or by means of a APPENDix transfer standard certified by this proce- CATIsBAToir PROcEDuRL FOR THE MEAsuRE. dure. Transfer standards must meet the re- oENT oF Ozo N THE ATosPHE quirements and specifications set forth In

AuTHORrT. Reference 8.

Section 109, 301 of the Clean Air Act 3. Apparatus. A complete UV calibration

system consists of an ozone generator, all as amended (42 USC 57409, 7601). output port or manifold, a photometer, an

- PSRIba FMNCIPLE appropriate source of zero air, 'and other

components as necessary. The configuration 1. Ambient air and ethylene are delivered must provide a stable ozone concentration

simultaneously to a mixing zone where the at the system output and allow the photom- ozone in the air reacts with the ethylene to eter to accurately assay the output concen. emit light, which is detected by-a photomul- tration to the precision specified for the tiplier tube. The resulting photocurrent is photometer (3.1). Figure 1 shows a common. amplified and is either read directly or dis- ly used configuration and serves to Illusplayed on a recorder. trate the calibration procedure which fol2. An analyzer based on this principle will lows. Other configurations may require ap be considered a reference method only If It propriate variations in the procedural steps. has been designated as a reference method AlU connections between components in the

in accordance with Part 53 of this chapter calibration system downstream of the Os

and calibrated as follows: generator should be of glass, Teflon, or

CALUMATION OCEVO other relatively inert materials. Additional

I information regarding the assembly of a UV

1. Principle. The calibration procedure is photometric calibration apparatus is given based on the photometric assay of ozone In Reference 9. For certification of transfer

(OW concentrations in a dynamic flow standards which provide their own source of

system. The concentratibn of 0. in an ab- 0,, the transfer standard may replaci the

sorption cell is determined from a measure- 0. generator and possibly other components meat of the amount of 254 nm light ab- shown n Figure 1; see Reference 8 for guidsorbed by the sample. This determination ance. requires knowledge of (1) the absorption o- 3.1 UV photometer. The photometer con- efficient (a) of 0, at 254nm, (2) the optical sists of a low.pressure mercury discharge path length (/)jhrough the sample, (3) the lamp, (optional) collimation optics, an ab, transmittance of the sample, at a wave- lenmtthaof25nm a the tplematurve- sorption cell, a detector, and sIgnal-process, length of pe4 m and (4) the temperature ing electronics, as Illustrated in Figure 1. It

transrmittance t and pressure Is defined (P) of, as the the sample. ratio The I/Io, must be capable of measuring the transmit tne,/,a aeegho 6 mwt

where I is the intensity of light which tance, ilL, at a wavelength of 254 nm wih

passes through the cell and is sensed by the sufficient precision such that the standard

detector when the cell contains an O. deviation of the concentration measuresample, and I0 is the intensity of light which meats does not exceed the greater of 0.005

passes through the cell and'Is sensed by the ppm or 3% of the concentration. Because

detector when the cell contains zeroAir. It Is the low-pressure mercury lamp radiates at

assumed that all conditions of the system, several wavelengths, the photometer must

except for the contents of the absorption incorporate suitable means to assure that

cell, are identical during measurement of I no 0. is generated In the cell by the lamp, and I. The quantities defined above are re- and that at least 99.5% of the radiation

lated by the Beer-'lambert absorption law, sensed by the detector Is 254 nm radiaton.

I -act (This can be readily achieved by prudent se- Transmittance = T (1) lection of optical filter and detector re- TO sponse characteristics.) The length of'the

light path through the absorption cell must where: be known with an accuracy of at 'loast

a=absorption coefficient of O at 254 99.5%. In addition, the cell and associated

nm=308+4 atm -' ca - 1 at 0"C and 760 plumbing must be designed to minimize loss

torr.ML Z%4 A of 0, from contact with cell walls and gas

c=O concentration In atmospheres handling components. See Reference 9 for

1= optical path length in cm additional information.

3.2 Air flow controllers. Devices capable in practice 6,cntao generator is used of regulating air flows.as necessary to meet quired ange. Each 0, concentration is de- the output stability and photometer precltermined from the measurement, of the sion requirements.

transmittance (I/L) of the sample at 254 am 3.3 Ozone generator. Device capable of

with a photometer of path length I and cal- generating stable levels of 0, over the reculated from the equation, quired concentration range, 3.4 Output manifold. The output mani.

c(atm) = (In I/IO) (2a) fold should be constructed of glass, Teflon,

at, ,, or other relatively inert material, and

or, should be of sufficient diameter to insure a o ,~ negligible pressure drop at the photometer , 2 connection and other output ports. The c(ppm) = ]0 0 (in (2b) system must have a vent designed to Insure :0 atmospheric pressure in the manifold and to

The calculated 0. concentrations must be prevent ambient air from entering the mani.'

corrected for 03 losses which may occur in fold.

FEDERAL REGISTER, VOL 44; NO. 28-THURSDAY, FEBRUARY 8, 1979

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RULES AND REGULATIONS

3.5 Two-wqay valve. Manual or auton

valve, or other means to switch the pho

eter flow between zero air and the O

centration.

3.6 Temperature indicator. Accura

+_1C. --

3.7 Barometer or pressure indicator.

curate to -- 2 torr. - 4. Reagents. 4.1 Zero air. The zero air must be fr(

contaminants which would cause a de

able response from the O. analyzer, ax should be free of NO, C.t, and other spc which react with Os. A procedure for ge

ating suitable zero air is given in Referen,

As shown in Figure 1, the zero air supplie

the photometer cell for the 1. refer - measurement must be derived from same source as the zero air used for get

tion of the ozone concentration to bc

sayed (I measurement). When using

photometer. to certify a transfer stan

having- its own source of ozone, see Ri ence 8 for guidance on meeting this reqi

ment.

5. Procedure.

5.1 General operation. The calibra

photometer must be dedicated exclusi

to use as a calibration standard. It sh,

always be used with clean, filtered call

tion gases, and never used for ambien

sampling. Consideration should be give

locating the calibration photometer I

clean laboratory where it can be station

protected'from physical shock, operatei- a responsible analyst, and used as a cons standard for all field calibrations via tr

fer standards.

5.2 Preparation. Proper operation of

photometer is of critical importance to

accuracy of this procedure. The follo

steps will help to verify proper operal

The steps are not necessarily required r to each use of the photometer. Upon in

operation of the photometer, these s should be carried out frequently, witt

quantitative results or indications recoi

in a chronological record either in tab

form or plotted on a graphical chart. As

performance and stability record of

photometer is established, the frequenc these steps may be reduced consistent, - the documented stability of the photomt 5.2.1 Instruction manual: Carry out

set-up and adjustment procedures or chi as described in the operation or instruc

manual associated with the photometer. 5.2.2 System check: Check the phot

eter system for integrity, leaks, cleanlft

proper flowrates; etc. Service or replace

ters and zero air scrubbers or other cons able materials, as necessary.' 5.2.3 idnearity. Verify that the phot

eter manufacturer has adequately es lished that the linearity error of the I

tometer is less than 3%, or test the lines

by dilution as follows: Generate and a an 03 concentration near the upper rz limit of the system (0.5 or 1.0 ppm), ther

curately dilute that concentration with!

air and reassay it. Repeat at several dliJ

ent dilution ratios. Compare the assal

the original concentration with the assa the diluted concentration divided by thi

lution ratio, as follows

.- A2lR

E =-A E=AAA1 1 x 100%

where:

E=linearity error, percent

A,=assay of the original ooncentration

A,=assay of the diluted concentration

R=dilution rato=flow of original concen- tration 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 meas- ured this way, the test Is not necessarily

conclusive. Additional Information on verifying linearity is contained in Reference 9.

5.2.4 Intercomparlson: 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

0, 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 0, concentration. This loss must not

exceed 5%. Some guidelines for quantitatively determliing this loss are discussed in

Reference 9.

5.3 Assay of 0 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. P 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.

5.3.3 Insure that the flowrate into the

[ ] 1 in ) T 760 10

0

where:

[Oaow=O, concentration, ppm

a=absorption coefficient of 0, at 254

nm=308 atnr- cmn- at O'C and 760 torr

1 -optical path length, cm T.=sample temperature, K

P=sample pressure, torr

L'=correctlon factor for 0, losses from

5.2.5=(l-fractlon 0 lost).

NoT&--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 re- quired for equation 4 Is obtained, either

automatically by the photometer or man. ually. For "automatic" photometers which

evaluate the first term of equation 4 based on a linear approximation, a manual correc- tion may'be required, particularly at higher

0, levels. See the photometer Instruction

manual and Reference 9 for guidance.

5.3.11 Obtain additional 0, 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 accordoutput manifold is at least 1 liter/min great- er than the total flowrate required by the

photometer and any other flow demand

connected to the manifold.

5.3A Insure that the flowrate of zero air,

P,, is at least 1 lter/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 alr, then F,. The two photometer readings must be equal (=lf).

Nox.-In some commercially available

photometers, the operation of the two-way

valve and various other operations in sec- tion 5.3 may be carried out automatically by

the photometer.

5.3.6 Adjust the 0. generator to produce an 0. 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,.

5.3.8 Actuate the two-way valve to-allow

the photometer to sample the ozone concen- tration until the absorption cell is thoroughly flushed and record the stable meas- ured value of L 5.3.9 Record the temperature and pres- sure of the sample in the photometer absorption celL (See Reference 9 for guidance.)

5.3.10 Calculate the 0, concentration

from equation 4. An average of several determinations will provide better precision.

(4)

Leg 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 theO,, ana- lyzer and the photometer or transfer standard to warmup and stabilize.

5.5.2 Allow the 0 analyzer to sample zero air until a stable response Is obtained

and adjust the 0. 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 0. concentration

standard of approximately 80% of the desired upper range limit (URL) of the 0. ana- lyzer. Allow the 0. analyzer-to sample this

0, concentration standard until a stable re- sponse is obtained.

5.5.4 Adjust the 0, analyzer's span con- trol to obtain a convenient recorder re- sponse as indicated below:.

e 0

3 IOUT recorder response (00 scale) (-j-X UK 100) + Z (5)

where:

(3) URL=upper range limit of the 0. analyzer, ppm

Z=recorder response with zero air, % scale

Record the 0. concentration and the cor- responding analyzer response. If substantial

adjustment of the span control Is necessary. L recheck the zero and span adjustments by

repeating steps 5.5.2 to 5.5.4.

5.5.5 Generate several other 0. concen- tration standards (at least 5 others are rec- ommended) over the scale range of the 0.

analyzer by adjusting the 0. source or by

Option 1. For each 0. concentration standard. record the 0 and the corresponding

analyzer response.

FEDERAL REGISTER, VOL 44, NO. 28-TMUDAY, FEBRUARY 8, 1979

8225

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8226 -RULES AND REGULATIONS

5.5.6 Plot the 0 analyzer responses versus the corresponding 0. concentrations

and draw the 0. analyzer's calibration curve

or calculate the appropriate response factor.

5.5.7 Option 1: The various 0, concentrations required in steps 5.3.11 and 5.5.5 may

be obtained by dilution of the 0. 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 0, generator. A mixing chamber between the O generator and the

output manifold is also required. The flowrate through the 0. generator (Fo) and the

dilution air Jlowrate (FD) are measured with

a reliable flow or volume standard traceable

to 2NBS. Each 0. concefntration generated by

dilution is-calculated from:

, F0

[03]OUT = [03OUT (FOFDO (6)

where:

[0.l'ouT'diluted 0. concentration, ppm

F=flowrate through the -0. generator,

liter/min

FD=diluent air flowrate. liter/min

REFERNCEs

1. E.C.Y. Inn and ". Tanaka, "Absorption

coefficient of Ozone in the Ultraviolet and

Visible Regions", . 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. (I;ondon), 78,

,932 (1961).

3. W. B. DeMore and 0. Raper, "Hartley Band Extinction Coefficients of Ozone in

the Gas Phase and in Liquid Nitrogen,

Carbon Monoxide, and Argon", J..Phys.

I Cherm, 68, 412 (1964).

4. M. Griggs, "Absorption Coefficients of

Ozone in the Ultraviolet and Visible Regions", 3. 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 Chen. Kinetics, VI. 725 (1974).

6. M. A. A. Clyne and J. A. Coxom, "Kinetic Studies of Oxy-halogen Radical Systems",

P-oc. 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", . Che7m.

Phys., 59, 1203 (1973).

8. "Transfer Standards for Calibration of

Ambient Air Monitoring Analyzers for

Ozone", EPA Publication available from

EPA, Department E (MD-77), Research Triangle Park, N.C. 27711.

9. "Teclhical Assistance Document for

'the Calibration of Ambient Ozone Monitors". EPA Publication available from EPA,

Department E (MD-77), Research Triangle

Park, N.C. 27711.

FEDERAL RIEGISTER, VOL,44, NO. 28--THURSDAY, FEBRUARY 8, 1979

HeinOnline -- 44 Fed. Reg. 8226 1979
RULES AND REGULATIONS 8227

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FEDERAL REGISTER, VOL 44, NO. 28-THUXSDAY, FEBRUARY , 1979

HeinOnline -- 44 Fed. Reg. 8227 1979
8228

Temporary Alternative Calibration procedure-(Bofic Acid-Potassium Iodide). This

procedure may be used as an alternative to

the Ultraviolet Photometry procedure for

direct calibration of ozone analyzers-but

not to certify transfer standards-until [18

months after the date. of final promulgation]. After that time this procedure can be

used only as a transfer standard in accord- ance with the guidance and specifications

set forth in Reference 4, "Transfer Standards for Calibration of Ambient Air Monitoring Analyzers for Ozone".

1. Principle. This calibration procedure (1)

is based upon the reaction between ozone (0s) and potassium iodide (KI) to release

iodine (I.) according to the stoichiometric

equation: (2) .

03 + 21- + 2H+ 12 + H2 0 + 02

The stoichiometry is such that the amount

of I. released is equivalent to the amount of

0,, absorbed. Ozone is absorbed in a 0.1M

boric acid (HBO.) solution containing 1%

KI, and the I. released reacts with excess iodide 'ion (I-) to form triodide ion (I-s)

which is measured spectrophotometrically

at a wavelength of 352 n. The output of a stable 0. generator is assayed in this

manner, and the generator is immediately

used to calibrate the 02 analyzer. The 0,

generator must be used immediately after

calibration and without physical movement,

and it is recalibrated prior to each use. Alternatively, the 0, analyzer may be calibrated by assaying the 0. concentrations using

the prescribed procedure while simultaneously measuring the corresponding 0.

analyzer responses. Ozone concentration

standards may also be generated by an optional dilution technique. With this option,

the highest 0, concentration standard is as- sayed using the prescribed procedure. The

additional 0. concentration 'standards re- quired are then obtained by dilution.

2. Appai-atus. Figures 1 and 2 illustrate a typical BAKI 0, calibration system and

show the suggested configuration of the

components listed below. All connections between components downstream of the 03

generator should be of glass, Teflon or other relatively inert material.

2.1 Air flow controller. Device capable of

maintaining a constant air flowrate through

the 0. generator within ±2%.

2.2 Air flowmeter. Calibrated flowmeter

capable of measuring and monitoring the

air flowrate through the 0. ,generator

within ±2%.

2.3 Ozone generator. Device capable of

generating stable levels of O'over the re- quired concentration range.

2.4 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 analyzer connec- tion. The system must have a vent designed

to insure atmospheric pressure in the manifold and to prevent ambient air from entering the manifold.

2.5 Impingers.. All glass impingers with

the specifications indicated in Figure 2 are recommended., The impingers may be purchased from most major glassware suppli-

,ers. Two impingers connected in series are used to insure complete collection of the

sample.,

RULES AND REGULATIONS

2.6 Air pump and flow controller. Any

pump and flow control device capable of

maintaining a constant flowrate of 0.4-0.6

'liter-mi through the impingers may be

used. A critical orifice as described by Lodge et a! (3) is recommended. The orifice should

be protected against moisture and particulate matter with a membrane filter or moisture trap containing Drierite, silica gel, or glass wool. The air pump must be capable of

maintaining a pressure differential of at

least 0.6-0.7 atmospheres across the critical

orifice. Alternatively, a needle valve could

be used with the pump to adjust the flow

through the impingers. A flowmeter is then

recommended to monitor the flow. The

needle valve-flowmeter combination should

be protected against moisture and particulate matter with a membrane filter or moisture trap.

2.7 Thermometer. Accurate to ±1"C.

"2.8 Barometer. Accurate to ±2 torr.

2.9 Volumetric flasks (Class A). 25, 100,

200, 500, 1000-ml.

2.10 Pipets (Class A). 1,.5, 10, 15, 20, and

25-ml volumetric, 1-ml or 10-ml graduated.

2.11 Spectrometer. Capable of measuring

absorbance at 352 nm with an absolute accu- racy of ±1% and linear response over the

range of 0-1.0 absorbance units. The photometric accuracy may be checked using optical glass filters which have certified absorbance values at specified wavelengths.

Matched 1-cm or 2-cm cells should be used

for all absorbance determinations.

3. Reagents.

3.1 Zero air. The zero air must be free of

contaminants which will cause a detectable

response of the 0, analyzer or which might

react with 1% BAKI. Air meeting this re- quirement may be obtained by: (1) passing it

through silica gel for drying, (2) treating It

with 0. to convert any nitric oxide (NO) to

nitrogen dioxide (NO,);' (3) passing it

through activated charcoal (6-14 mesh) and

molecular sieve (6-16 mesh, type 4A) to remove any NO,, hydrocarbons, and traces

of water vapor;, and (4) passing it through a 2-micron filter to remove any particulate

matter.

3.2 Boric acid (H.BO,), ACS reagent

grade. , J

3.3 Potassium iodide (HI), ACS reagent

grade.

3.4 Hydrogfen peroxide (H20), ACS reagent grade;-3% or 30%.

3.5 Potassium iodate (KIO), ACS rea- gent grade certified 0.1N.

3.6 Sulfuric acid (HSO.), ACS reagent

grade, 95% to 98%.

3.7 Distilled water. Used for preparation

of all reagents.

3.8 Absorbing reagent. Dissolve 6.2 g of

boric acid (HBO.) in approximately 750 ml

of distilled water in an amber 1000-mI volumetric flask. The flask may be heated

gently to speed dissolution of the HBO.,

but the solution must then be cooled to room temperature or below before proceeding with the reagent preparation. [While

the HBO. solution is cooling, prepare the

hydrogen peroxide (H,,). solution according to the directions in 3.9.] When the

H.BO. solution has cooled, add 10 g of po- tassium Iodide (HI) to the HBO. solution

and dissolve. Add 1 ml of 0.0021% H10 solution (see 3.9) and mix thoroughly. Within 5

minutes after adding the peroxide, dilute to

volume with distilled water, mix, anddetermine the absorbance of this BAKI solution

at 352 nm against distilled water as the reference. The pH of the BAKI solution should

be 5.1±0.2.

, Set 'the absorbing solution aside for 2

hours and then redetermine the absorbance

at 352 nm against distilled water as the ref. erence. If the resultant absorbance from

this second determination is at least 0,008

absorbance units/cm greater than the first

determination, the absorbing reagent is

ready for use. If no increase or an increase

of less than 0.008 absorbance units/cm Is ob.

served, the KI reagent probably contains an excessive amount of a reducing contaminant

and -must be discarded. In this event, prepare fresh absorbing reagent using a different numbered lot of KI. If unacceptable absorbing reagent results from different lots

of HI, test the possibility of contamination

In the HIBO, by using a dlfferen~numbered

lot of HBO.

3.9 Hydrogen peroxide solution 0.0021%.

Using a graduated pipet, add 0.7 ml of 30% or 7.0 ml of 3% hydrogen peroxide (11.0) to

approximately 200 ml of distilled water in a 500-ml volumetric flask, dilute to volume

with distilled water and mix thoroughly. To

prepare-the 0.0021% solution, pipet 5 ml of

the above solution into 50 ml of distilled

water in a 100-ml volumetric flask, dilute to

volume with distilled water, and mix thoroughly. This 0.0021% 11,0, solution must be

prepared fresh each time a fresh batch of

absorbing reagent is prepared. Therefore,

the remaining contents of both volumetrio

flasks should be discarded after treatment

of the BAKI absorbing reagent (see 3.8).

3.10 Standard potassium Iodate solution

(0.1N). Use a commercial standard solution

of potassium Iodate (KIO,) having a certl.

fled normality. 3.11 Sulfuric acid (UN). Dilute 28 ml of

concentrated (95-98%) sulfuric acid (HSO,)

to volume in a 1000-ml volumetric flask.

4. Procedure.

4.1 Assemble an ozone calibration system

such as shown in Figure 1.

4.2 Assemble the HI sampling train such

as shown in Figure 2. All connections between the various components must be leak

tight and may be made using grease-free

ball joint fittings, heat-shrinkable Teflon

tubing, or Teflon tube fittings. The conne-. tion to the 0. output manifold should be

made using 6 mm ( / in.) Teflon tubing not

to exceed 1.5 meters in length.

4.3 Calibrate all flowmeters and critical

orfices under the conditions of use against a

reliable flow or volume standard such as a NBS traceable bubble flowmeter or wet-test

meter. Correct all volumetric flowrates to

25°C and 760 torr as follows:

PS " PH20 298 FR= FS x 760 X T+273

where:

F5 =flowrate corrected to reference conditions (25" C and 760 torr), liter/min

Fs=flbwrate at sampling conditions, liter/

min

Ps=barometric pressure at sampling con- ditions, torr

P,,,=vapor pressure of H, at T,. torr (For

wet volume standard. For a dry standard, P,,.=O)

T,=.temperature at sampling conditions, "0

r. -

FEDERAL REGISTER, VOL 44, NO. 28-THURSDAY, FEBRUARY 8, 1979

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RULES AND REGULATIONS

4.4 KI calibration curve. 4.4.1 Prepare iodine standards, fresh

when needed, as follows:

A. Accurately pipet 10 ml of 0.1N standard

potassium iodate (KIO.) solution into a 100-

nl volumetric flask containing approximately 50 ml of distilled water. Add 1 g of potassium iodide (KI) and 5 ml of IN sulfuric

acid (HO,), dilute to volume with distilled

water, and mix thoroughly.

B. Immediately before use, pipet 10 ml of

the iodine (I) solution prepared in step A

above into a 100-ml volumetric flask and

dilute to volume with absorbing reagent.

Then further dilute this solution by pipetting 10 ml of it into a 200-ml volumetric

flsk and diluting it to volume with absorbing reagent.

C. In turn, pipet 5, 10, 15. 20, and 25 ml

aliquots of the final I solution prepared In

step B above into a series of 25-ml volumetric flasks. Dilute each to volume with absorbing reagent and mix thoroughly. To

prevent I. losses by volatilization, the flasks

should remain stoppered until absorbance

measurements are made. Absorbance measurements (see 4.4.2) should be taken within

20 minutes after preparation of the I standards.

4.4.2 Determine the absorbance of each

I standard at 352 nm. Also measure the absorbance of a sample of unexposed absorbing reagent. Determine the net absorbance

of each I standard as:

Ssarple ( Iunexposed

net absorbance absorbancel- reagent I

S ~~rnc- 1 absorbance

4.4.3 For each I. standard, calculate the

net absorbance/cm as:

net absorbance/cm = net absorbance b

where:

b=spectrophotometer cell path length, cm4.4.4 For each I. standard. calculate the

I. concentration in mole/liter as:

I equivalpnt 12 1 r-oc 12 C 1 2 1 i V,1 0 3 x T -- eq u t a -t 10 ' 3 ' - e q v a l e n t 1 ,

10 ia 10 -i -1 _ - X

= NKIO3 x Vi x 10-5

where:

[I,12=concentration of each I2 standard,

mole Idliter

N..o3=normallty of KIO, (from 3.10).

equivalent liter

V,=volume of I, solution (from step

4.4.1.0)=5, 10. 15, 20, or 25 ml,

4.4.5 Plot net absorbance/cm (y.axls) versus the mole Idlter (x-axis) for each L

standard and draw the KI calibration curve. Calculate the slope of the curve In liter

mole-' cm-' and record as S, The value of

the slope should be 26,000±780. If the

slope is not within this range, and the photometric accuracy of the spectrophotometer

meets the specifications given in 2.11, repeat

the procedure using freshly prepared I,

standards. If the slope is still not within the

specified range, repeat the procedure using a different lot of certified 0.1N KIO, to prepare the I. standards.

4.5 Calibration of the ozone generator.

4.5.1 Adjust the air flow through the 0,

generator to the desired flowrate and record as F.. At all times the air flow through the

generator must be greater than the total

flow required by the sampling Mstems, to assure exhaust flow at the vent.

4.5.2 With the 0, generator olf. flush the

system with zero air for at least 15 minutes

to remove residual 0. Pipet 10 ml of absorbing reagent into each of 2 impingers and

connect them--into the sampling train as shown In Figure 2. Draw air from the

output manifold of the 0, calibration

system through the sampling train at 0.4-

0.6 liter/ain for 10 minutes. Immediately

transfer the exposed solutions to clean spectrophotometer cells. Determine the net absorbance (sample absorbance-unexposed

reagent absorbance) of each solution at 352

nm,' thin three minutes. Add the net absorbances of the two solutions to obtain the

total net absorbance. Calculate the ldicated 0, concentration (system blink) as equiv-

* alent 0, concentration according to 4.5.4. If

the system blank Is greater than 0.005 ppm

0,, continue flushing the O, generation

system for an additional 30 minutes and re- determine the system blank. If the system

blank is still greater than 0.005 ppm 0,. the zero air probably contains traces of an oxidizing contaminant, and the activated charcoal and molecular sieve (see 3.1) should be

replaced.

4.5.3 Adjust the 0. generator to generate

* an 0, concentration In the range of interest

and allow the system to equilibrate for

about 15 minutes. The uncalibrated 0, ana- lyzer to be calibrated can conveniently be

used to Indicate the stability of the 0, generator output, When the O, generator

output has stabilized. pipet 10 ml of absorbIng reagent into each Impinger. Draw 0.

from the output manifold of the 0, calibratIon system through the sampling train at

0.4-0.6 lIter/mLn. Use a sample time of between 10 and 30 minutes such that a total

net absorbance between 0.1 and 1.0 absorbance units is obtained. (At an 0 concentration of 0.1 ppm and a sampling rate of 0.5

liter/min. a total net absorbane >0.1 absorbance units should be obtained If a sampling

time of 20 minutes and 1-cm spectrophotometer cells are used.) Immediately after collection, transfer the exposed solutions' to

clean spectrophotometer cells. Determine

the net absorbance (sample absorbance-unexposed reagent absorbance) of each solution at 352 nm within three minutes. Add

the net absorbances of the two solutions to

obtain the total net absorbance.

4.5.4 Calculation of ozone concentration.

4.5.4.1 Calculate the total volume of air.

sampled, corrected to reference conditions

of 25*C and 760 tor" as:

VR = FR X t S

where:

Vx=volume of air sampled, corrected to

reference conditions, liter

Fj.=sampling flowrate corrected to refer- ence conditions, liter/min

ts-=mpling time. min

4.5.4.2 Calculate the I, released in moles

as:

31e I = total net absorbancex 0.01

2 S cx b

where: total net absorbance=sum. of net absorbances for the two solutions

0.01=volume of absorbing reagent in each

Impinger, liter

S,=sloe of Kr calibration curve, liter

mole- 'cm

b=spectrophotometer cell path length, cm

4.5.4.3 Calculate the tZ of 0, absorbed as:

or - e I ee0 3 24.471G 106 

1.1 3 2 T-=Me-r -=-e-3 1 0

or,

I' 03 ' role 12 24.47 x 106

4.5.4.4

ppm as:

Calculate the 0, concentration in

P1 pp 0 3 03 = 7R

4.5.5 Repeat steps 4.5.3 and 4.5.4 at least one more time at the same 0. generator setting. Average the two (or more) determinations and record the average along with the

0, generator setting.

4.5.6 Adjust the 0, generator to obtain

other 0, concentrations over the desired

range. Determine each 0. concentration

using the procedure given above. Five or more 0, concentrations are recommended.

Plot the 0, concentrations versus the corre- sponding 0, generator setting and draw the

0, generator calibration curve.

4.6 Calibration of the ozone analyzer. 4.6.1 Allow sufficient time for the 0. analyzer to warm-up and stabilize.

4.6.2 Allow the 0, analyzer to sample zero air until a stable response is obtained

and adjust the 0, 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'.

4.6.3 Using the 0. generator as calibrated

above and the same P.. generate an 0, con- centration near 80% of the desired upper

range limit CURL) of the 0, analyzer.

4.6.4 Allow the 0, analyzer to sample

this 0, concentration until a stable response

is obtained. Adjust the analyzer's span con- trol to obtain a convenient recorder response as indicated below:

FEDERAL REGISTER VOL 44, NO. 28-THURSDAY, FEBRUARY 8, 1979

8229

HeinOnline -- 44 Fed. Reg. 8229 1979
RULES AND REGULATIONS

(030UT • recorder response (% scale) = .URL x 100) + Z

[O]ouT=O, concentration at the output

manifold, ppm URL = upper range limit

of the 0 analyzer, ppm, Z - recorder

response with zero air, % scale.

Record the 0. concentration and the 0.

analyzer response. If substantial adjustment

of the span control is necessary, recheck the zero and span adjustments .by repeating

steps 4.6.2 through 4.6.4.

4.6.5 Generate several other O concen- trations (at least 5 others are recommended)

over the scale range of the 0, analyzer by

adjusting the 0, generator settings (preferably the same settings as used in 4.5) or by

Option 1. For each 0. concentration, allow

for a-stable analyzer response, then record

the. response and.the corresponding 0. con- centration.

-4.6.6 Plot the 0. analyzer responses

versus the corresponding 0. concentrations

and draw the 0. analyzer's calibration curve

or calculate the appropriate response factor.

4.6.7 Option .: The variods 0. concentrations required in step 4.6.5 may be obtained

by dilution of the O. concentration generated in 4.6.3. With this option, accurate flow

measurements are required. The dynamic

calibration system must be modified as shown in Figure 3 to allow for dilution air to

be metered in downstream of the 0. generator. A mixing chamber between the O generator and the output manifold s also re- quired. The flowrate through the O generator (Fo) and the dilution air flowrate (FD) are measured with a reliable .flow or volume

standard traceable to NBS. The highest 0.

concentration standard requir6d (80% URL)

is assayed, according to the procedure In 4.5.

Each 0. concentration generated by dilution

is calculated from:

F0 [03]OUT = [

0 3OUT ,F + FD)

where: [O,'Jtru =' diluted 0, concentration,

ppm; F. = flowrate through the 0. generator. liter/min; FD = diluent air flowrate,

liter/mIn. * ' NoTL--Direct calibration of the 0. analyz- er may also be accomplished by hssaying the 03 concentrations using the procedure in 4.5

while simultaneously measuring the corre- sponding 0. analyzer responses as specified

in 4.6.

REFERENCES

1. D. L. Flamm, "Analysis of Ozone at Low

Concentrations with Boric Acid Buffered

KI," Environ. Sci. TechnoL, 11, 978 (1977).

2. B. E. Saltzman and N. Gilbert, "lodometric Microdetermination of Organic Oxidants and Ozone," Anal. Chen., 31, 1914

(1959).

3. J. P. Lodge, Jr., J. B. Pate, B. E.

Ammons, and G. A. Swanson, "The Use of

Hypodermic Needles as Critical Orifices in

Air Sampling," J Air Poll. Control Assoc.,

16, 197 (1966).

4. "Transfer Standards for Calibration of

Ambient Air Monitoring Analyzers for

Ozone," EPA Publication available from

EPA, Department E(MD-77), Research Triangle Park, N.C. 27711.

FEDERAL .REGISTER, VOL 44, NO. 28--THURSDAY, FEBRUARY 8, 1979

8230

HeinOnline -- 44 Fed. Reg. 8230 1979
RULES AND REGULATIONS

[6568-01-C]

2

VENT

EXTRA OUTLETS CAPPEO

WHEN NOT IN USE TO INLET OF

KI SAMPLING TRAIN

Fiqure I Schun;atic diaqrain of a typc ii BAKI calibraion sistem

FEDERAL REGISTER, VOL 44, NO. 23-THURSDAY, FEBRUARY 8, 1979

03

GENERATOR

OUTPUT

MANI FOLD

8231

HeinOnline -- 44 Fed. Reg. 8231 1979
RULES AND REGULATIONS

TO AIR

SPUMP

MEMBRANE

FILTER

CRITICAL ORIFICE FLOW CONTROL

5 mm I.D.- . -

IMPINGERS

(SEE BELOW)

_10 mm O.D.

1 24/40, CONCENTRIC WITH

OUTER PIECE'AND WITH

NOZZLE ,

GRADUATIONS AT 5 ml

INTERVALS. ALL THE

WAY AROUND

II NOZZLEID EXACTLY

S--j 1mm. PASSES 0.09 TO 0 I

S icfm AT 12 in H20 VACUUM;

PIECES SHOULD BE INTERCHAtJGEABLE. MAINTAINING

NOZZLE CENTERING AND.

5mm CLEARANCE TO BOTTOM

0 D INSIDE SURFACE

TRAP

TO AIR

PUMP

NEEDLE VALVE

ALTERNATE FLOW CONTROL

ALL GLASS MIDGET IMPINGER (THIS IS A COMMERCIALLY

STOCKED ITEM).

Figure 2 KI sampling train.

FEDERAL REGISTER, VOL 44, NO. 28-THURSDAY, FEBRUARY 8, 1979

8232

20 ml

10 ml

30 ml

20 ml

10 ml

CLEARANCE

3TO 5mm

HeinOnline -- 44 Fed. Reg. 8232 1979
RULES AND REGULATIONS

S F0O i

CHAMBER

OUTPUT

MANIFOLD

VENT -4

EXTRA OUTLETS CAPPED

WHEN NOT IN USE

TO INLET OF TO INLET OF ANJALYZER

KI-SAMPLING TRAIN UNDER CALIBRATION

FPiqure-3 Schematic dhaqrdni of d tymcll BAKI cdlbration system (Option 1)

rFR Doe. '79-4057 Filed 2-7-79; 8:45 am] r

FEDERAL REGISTER, VOL 44, NO. 28-THURSDAY, FEBRUARY 8, 1979

ZERO

AIR

8233

HeinOnline -- 44 Fed. Reg. 8233 1979