### RULES AND REGULATIONS

number ofdayswith maximumhourly aver- age ozone concentrations above the level of the standard" may be simply stated as the "expected numberofexceedances."

The basic principle in making this determination isrelatively straightforward. Most. ofthe complications that arise In determining the expected number of annual exceed-

ances relate to accounting for incomplete sampling. Ingenera], theaverage number of exceedances per calendar yearmusthe less thanor equal to 1. In Itssimplestform,,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 equalto 1.
2. Interpretation of

ExpectedExceedances
The ozone- standard states that the ex- pected number of exceedances per year must beless than or equal to1. 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 ofstandard. Supposea monitoringstationrecords avalid daily maximum hourly average ozone value for every dayof theyear during the past 3 years. At the end ofeach year, the number of daysr with-maximum hourly concentrations above 0.12ppm is determined and this number is averaged with theresults ofprevious years. Aslong asthis averageremains "lessthan or equal to 1" the area isIncom- pliance.
3. Estimating the Number ofExceedances

foraYear
Ingeneral, a valid daily maximum hourly average valuemay notbe available for each day ofthe year, and it will benecessary 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 ofexceedancesper yearis 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 theprocedures ofthis sectionto accountforincomplete 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 beenmissed butin other cases
no measurement mayhave been scheduled forthat day.A daily maximum ozone value is defined to-be the highest hourly ozone value recordedfortheday.This dailymaxi-
mum value is considered to be valid If 75 percent ofthe hours from 9:01 am. to 9:00 p.m. (MST)weremeasured or ifthe highest -hour is greater than thp level ofthe standard.

In some areas, the seasonal pattern of

ozone is so pronounced that entire months need notbe sampled because it is extremely unlikely thatthe standard wouldbe exceeded. Any such waiver of the ozone monitoring requirement would be handled under provisions of 40 CFR Part 58. Some allow-

ance should alsobemade for daysfor which valid daily maximumhourly values werenot obtained but which would quite likely have been below thestandard. Suchan allowance introduces a complication inthat it becomes necessary todefine underwhat conditions a missingvalue maybe assumed to havebeen less than the level ofthestandard. The following criterion maybeusedfor ozone: A missing daily maximum ozone value may be assumed to beless than the level of the standard f the valid daily maxima on both the preceding day and the following day do notexceed 75 percent ofthe levelof thestandard.

Letz denote the number ofmissing daily maximumvalues thatmaybe assumed tobe less than the standard. Then the following formula shall be used to estimate the ex- pected number ofexceedances for the year e=v+£E(v/n)'(N-n-z)] (1)
(Indicates multiplication.)
Where:

e=the estimated number of exceedances

fortheyear, N=the number of required monitoring.

daysin theyear. n=the numberofvaliddailymaxima, v=the number of daily values above the

level-of thestandard; and z=the number ofdays assumed to beless

thanthe standa-d level.
*Indicatesmultiplication. This estimated number of exceedances shall be rounded to one decimal place (fractional parts equal to0.05 roundup).

It should benoted thatN will be thetotal number of days in the year unless the appropriate Regional Administrator has granted awaiver undertheprovisions of40 CFR Part58.

The above equationmay beinterpreted 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 yearbut a certain number of these, namely z. were assumed to be less than the standard. Therefore, (N-n-z) imingvalues are considered toinclude possible exceedances. The fraction of measured values that are above the levelofthe standard isv/n. It is assumed that this same fraction applies to the (N-n-z) missing values and that (v/n)'(N-n-z) ofthese valueswould 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).

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


### [6560-01-M]

FRL1018-31



### PART 50-NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY STANDARDS
Calibration of Ozone Reference Methods AGENCY: U.S. EnvironmentalProtectionAgency. ACTION: Finalrule. 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 beused forcalibrating those ozonereference methods. EPA has evidence that another calibration procedure for

ozone reference methods is significantly more accurate and less variable than theprocedure 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 ultravioletphotometry. EFFECTIVEDATE: This action is effective immediately upon publication because the revised standard to which It appliesIsimmediately 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 ofTitle 40, Chapter I of the Code of Federal Regulations specifies the National Ambient Air Quality Standards forseveral airpollutants 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 ofozone 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, andaccordingly EPA proposed an amendment to Appendix D toreplace the NBKIprocedure with the new procedure, based on ultraviolet (UV) photometry (43 FR 26971- 26984). Therationale forthe proposed amendment was discussed In -thepreamble tothatproposal. 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 formerlyused inPart 50.

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

### 8, 1979

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### 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 asfollows:

(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 theUV procedure itself is thus referred to as a "UV standard" for ozone.

(2) Independent use of a manual KI procedure known as the "BAKIprocedure" in lieu oftheUV 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) Theuse ofalternative 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 aUV ozone standard and then used at another location toreproduce 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
Thenew UV calibration procedure is quite simple.After generating astable,

ozone concentration with an ozone generator, the operator assays it by passing all ora portion ofthe 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 somemay 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 isparticularly 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 ofcritical-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 ofan 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, mustbe 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 tobe "self-calibrated" even though it contains a UV photometer which meets the specifications of the UV calibration procedure.

NxvBAKI 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, theBAKI 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 asa 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 ofAmbient 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 ofit may be obtained from the address given at the beginning of this preamble.

SULVIARY OF COMMENTs RECEIVED AND CHANGES MADE TOFINAL 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 ofall 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
arediscussed 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 orrejection ofeach 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 isavailable forpublic inspection during normal business hours at the USEPA, CentralDocket 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 EPARegion, areference photometer that could be used to certify appropriate transfer standards. Other comments suggested asimilarneedfor -suchreference 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 toexperience changes in thewa- 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 iswith an absorbing gas such as ozone. The linearity test described in Section 5.2.3

serves thispurpose.

Therewas some concernforwhether 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 -procedurewere 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 wasfurther pointed out that,with certain configurations, some of the components shown In the suggested configuration might notbenec- essary, and some of the procedural steps in the proposed procedure might notbenecessary or evenpossible. 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 mightconfuse 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 testin 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 at5% to allow forsome 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 ,8months.The respondent rec- ommended thatEPA 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 procedureismore variable thantheUV procedure but believes that some transition period isnecessary before the UV procedure is required exclusively. There were few comments to the con- trary. EPA considered allowing continued use oftheNBKI 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 thanthe 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 forclarification 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 orderthat they not be confused with equivalent weight. Also,the concentration ofthe hydrogen peroxide added in Section 3.8 has been increasedslightly andthe 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 standardsbased onmethodsknown 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 nomajor changes to the transfer standard con- cept as originallyproposed.

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. EPAhas re-evaluated thisposition. but as noted below, still discourages such attempted corrections.

EFcT ON NATIONAL AMIE TAIR

QUA YSTANDARD FOROZONE
Because of the substantial variability ofthe NBKI procedure andthe 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. EPAbelieves that supersession ofthe NBKI calibration procedure with the UV procedure should have no effect

on the magnitude oftheNational AmFEDERAL REGISTER, VOL 44, NO. 28-THURSDAY, FEBRUARY 8, 1979 

### .8223'

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### 8224

blent,AirQuality 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 thenew UV calibration procedure-even whenindividual agencies or laboratories try to determine a more precise, laboratoryspecificbias value.

EFFECTON CURRENTLY DESIGNATED REFERENCEAND 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 therevised 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 transferstandard 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 theirrespective manuals tospecify the UV procedure or certified transfer standards forcalibration. 

### EPAbelieves 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 ofthe sample. 2 Applicability. This procedure isapplica- 1. Appenidix D isrevised 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 FORTHEMEAsuRE. dure. Transfer standards must meet the re- oENT oFOzo N THEATosPHE quirements and specifications set forth In AuTHORrT. Reference 8. Section 109, 301 ofthe CleanAir Act 3.Apparatus. A complete UV calibration system consists of an ozone generator, all as amended (42USC 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 mixingzone where the at thesystem output and allow thephotom-
ozone in the airreacts with the ethylene to eter to accurately assay the output concen. emitlight,which isdetectedby-a photomul- tration to the precision specified for the tiplier tube. The resulting photocurrent is photometer (3.1). Figure 1 showsa common. amplified and is either read directly or dis- ly used configuration and serves to Illusplayedonarecorder. trate the calibration procedure which fol2.An analyzerbased on thisprinciplewill lows. Other configurations may require ap be considered areference method onlyIf It propriate variations in theprocedural steps. has been designated as areference method AlU connections between components in the in accordance with Part 53 of this chapter calibration system downstream of the Os andcalibrated asfollows: generator should be of glass, Teflon, or CALUMATION OCEVO other relatively inert materials. Additional 

### I information regarding the assembly ofa UV 1.Principle. The calibration procedure is photometric calibration apparatus is given based on the photometric assay of ozone InReference 9.For certification oftransfer (OW concentrations in a dynamic flow standards which provide theirown source of system. The concentratibn of 0. in an ab- 0,, the transfer standard may replaci the sorption cellis determined from a measure- 0.generator and possiblyother components meat of the amount of 254 nm light ab- shown n Figure 1; see Reference 8 forguidsorbed by the sample. This determination ance. requires knowledgeof (1) the absorption o- 3.1 UV photometer. The photometer con- efficient (a)of0, at 254nm, (2) theoptical 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 inFigure 1.It t and pressure (P) of,the sample.The must be capable ofmeasuring the transmit transrmittance Isdefined as the ratio I/Io, tne,/,a aeegho 6 mwt 

### where I is the intensity of light which tance, ilL, at awavelength of 254 nm wih passes throughthe cell andissensed bythe sufficient precision such that the standard detector when the cell contains an 

## O. deviation of the concentration measuresample, and I0isthe intensityoflightwhich meats does notexceed the greater of 0.005 passes throughthe cell and'Is sensedby the ppm or 3%of the concentration. Because detectorwhenthe cell containszeroAir. 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 bytheBeer-'lambert absorptionlaw, sensed by the detector Is 254 nmradiaton.

I -act (Thiscan bereadily achieved by prudentse- Transmittance = 

### T (1) lection of optical filter and detector re- TO sponse characteristics.) The length of'the lightpath 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 - 

### 1at 

### 0"C and 760 plumbing mustbe designed tominimize loss torr.ML Z%4 A of 

### 0, from contact with cell walls and gas 

### c=O concentration Inatmospheres handling components. SeeReference 9 for 1=optical pathlength incm additional information. 3.2 Air flow controllers. Devices capable inpractice 6,cntao generator is used ofregulating air flows.as necessary to meet quired ange. Each 0, concentration is de- the output stability and photometer precltermined from the measurement, of the sionrequirements. transmittance (I/L)ofthesample at254am 3.3 Ozone generator. Device capable of with aphotometer ofpath length Iand cal- generating stable levels of 0, over the reculated fromthe equation, quiredconcentration range, 3.4 Output manifold. The output mani. c(atm) = 

### (InI/I O

### ) (2a) fold should be constructed of glass, Teflon, at, ,, or other relatively inert material, and or, should be ofsufficient 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 inthemanifold and to The calculated 0. concentrations must be prevent ambient airfrom entering themani.' corrected for 03 losses which may occur in fold.

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### RULES AND REGULATIONS

3.5 Two-wqay valve. Manual or auton valve, or other means to switch thepho 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 mustbe fr( contaminants which would cause a de able response from the O. analyzer, ax should befree ofNO, C.t, and otherspc which react with Os. Aprocedure for ge ating suitablezero airisgiveninReferen, AsshowninFigure 1, thezero airsupplie the photometer cell for the 1. refer

- measurement must be derived from

same source as thezero air used forget 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 8for guidance onmeeting thisreqi 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-

aresponsible analyst, andused asa 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 arenot necessarily required r to each use ofthe 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 orplotted ona graphical chart.As performance and stability record of photometer is established, the frequenc these steps may be reduced consistent,

-the documented stability ofthephotomt 5.2.1 Instruction manual: Carry out set-up and adjustment procedures or chi

as described in the operation or instruc manual associated with thephotometer.

5.2.2 System check: Check the phot eter system for integrity, leaks, cleanlft proper flowrates; etc. Service or replace ters andzero air scrubbers or other cons able materials, asnecessary.'

5.2.3 idnearity. Verify that the phot eter manufacturer has adequately es lished that the linearity error of the I tometer is lessthan 3%, ortest thelines by dilution as follows: Generate and a
an 03 concentration near the upper rz limit ofthe 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 lutionratio, asfollows

.- 

### A 2lR E =-A AA1 x 100% 

### E=A1

where:

E=linearity error, percent A,=assay oftheoriginal ooncentration A,=assay ofthe dilutedconcentration R=dilution rato=flow oforiginal concen-

tration divided by thetotalflow
The linearity error mustbe 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 linearityiscontainedinReference 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 orlaboratories.

5.2.5 Ozone losses: Some portion of the 0, may belost upon contact with the photometer cell walls and gas handling components. The magnitude of this loss must be determined and used to correctthe calculated 0, concentration. This loss must not exceed 5%. Some guidelines for quantitatively determliing this loss are discussed in Reference 9.

5.3 Assay of0 concentrations. 5.3.1 Allow the photometer system to
warmup andstabilizer.

5.3.2 Verify that the flowrate through thephotometer absorption cell. P allowsthe cell to be flushed In a reasonably short period oftime (2lIter/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 withtime.

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 pathlength, 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 theoperator'sresponsibility 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 ofequation 4 based

on alinear approximation, a manual correc- tion may'be required, particularly at higher 0, levels. See the photometer Instruction manual andReference 9forguidance.

5.3.11 Obtain additional 0, concentration standards as necessary by repeating steps 5.3.6 to 5.3.10 orbyOption 1.

5.4 Certification oftransfer standards. A transfer standard iscertified byrelating the output of the transfer standard to one or more ozone standards as determined accordoutput manifold isatleast 1liter/min great-
er than the total flowrate required by the photometer and any other flow demand connected tothe manifold.

5.3A Insure thatthe flowrate ofzeroair, P,,is at least 1 lter/min greater than the flowrate requiredbythe 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 zeroalr, thenF,.Thetwo photometerreadings mustbeequal (=lf).

Nox.-In some commercially available photometers, the operation of the two-way valve and various other operations in sec- tion 5.3 may becarried outautomaticallyby thephotometer.

5.3.6 Adjust the 0. generator to produce

an 0.concentration asneeded.

5.3.7 Actuate the two-way valve to allow thephotometer to sample zero airuntil the absorption cell is thoroughly flushed and record thestable measured valueofI,.

5.3.8 Actuate the two-way valve to-allow thephotometer tosample the ozone concen- tration until the absorption cell is thoroughly flushed and record the stable meas- ured value ofL

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 willprovidebetterprecision.



### (4)

Leg to section 5.3. The exact procedure varies depending on the nature and design of thetransfer standard. ConsultReference 8forguidance.

5.5 Calibration ofozone analyzers. Ozone analyzers are calibrated as follows, using

ozone standards obtained directly according to section 5.3 or by means of a certified transferstandard.

5.5.1 AllowsufficienttimefortheO,, ana- lyzerand thephotometer ortransfer standardto warmupand 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 theanalyzer's zero adjustmentto +5% of scale is recommended to facilitate observing negative zero drift. Record the stablezero airresponseas "Z.

5.5.3 Generate an 0. concentration standard of approximately 80% of the desiredupper range limit(URL) ofthe 0. ana- lyzer. Allow the 0. analyzer-to sample this 0, concentration standard until a stable re- sponse isobtained.

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



### e 03 

### IOUT 

### recorder response 

## (00 scale) UK (-j-X 100) + 

### Z (5)

where: (3) URL=upper range limit ofthe 0. analyzer, ppm Z=recorder responsewith zeroair, %scale Record the 0. concentration and the cor- responding analyzer response. Ifsubstantial adjustment ofthespan control Isnecessary. L recheck the zero and span adjustments by repeating steps 5.5.2to 5.5.4. 5.5.5 Generate several other 0. concen- tration standards (atleast 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 analyzerresponse.

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

## 8225

HeinOnline -- 44 Fed. Reg. 8225 1979

### 8226 -RULES AND REGULATIONS

5.5.6 Plot the 0 analyzer responses
versus the corresponding 0. concentrations and drawthe 0. analyzer's calibration curve
or calculate the appropriate response factor.

5.5.7 Option1:The various 0, concentrations required in steps 5.3.11 and 5.5.5 may be obtained by dilution ofthe 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 fordilution airto be metered in downstream ofthe 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 airJlowrate (FD) are measured with

a reliable flow or volume standard traceable to2NBS. Each 0. concefntration generated by dilution is-calculated from:

, F0 

### [0

### 3]OUT = 

### [0

## 3OUT (FOFDO 

## (6)

where:

[0.l'ouT'diluted 0. concentration, ppm F=flowrate through the -0. generator,

liter/min FD=diluent airflowrate.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, andH.Seitz, "Ozone Olefin Reactions in the Gas Phase. 1.Rate Constants andActivation Energies". Int'lJour.ofChen. Kinetics, VI. 725 (1974). 6. M.A. A. Clyne andJ. A. Coxom, "Kinetic Studies ofOxy-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. TheUltraviolet 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

[6568-01-C] oo ut

"+FLOIY CEE ,O AI R " O ,rEXIF"A OUh I S CA. ,

I 

# I o-F1 &O A UI S



## , ETsC.T?'R CAMRII I" CELLI

S2G

'L I I I~tY -VL PHOTOMETER O~TR OKRLLR 

## ~

Figure 1 .&helimt&C d.ir ' of ,.3 Iyp.3l UV ahOineitliiC C~.slb'iltsc $'i$tIrn

EXTA O ITlSCUt

UJV

PHOT'OUIE [R 

## Iopt cs

DETETORASPPCCLL Qj

SIGAL F

PROCESSING I"X"AUST ELECTROICS

- I+

Figure 2. Sl hematiC diagarn of

. typic.lUV photOmet'ic €slltaOnsystm (OPT2OI ii

A

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 MonitoringAnalyzers forOzone".

1.Principle. This calibrationprocedure (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 awavelength 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, the0, 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 obtainedby dilution.

2. Appai-atus. Figures 1 and 2 illustrate a typical BAKI 0, calibration system and show the suggested configuration of the components listedbelow.All connections between components downstream of the 03 generator should be of glass, Teflon or otherrelatively inert material.

2.1 Air flow controller.Device capable of maintaining aconstant 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 ofglass, Teflon,

orotherrelatively inert material and should be of sufficient diameter to insure anegligible pressure drop at the analyzer connec- tion. The system musthave a vent designed to insure atmospheric pressure in the manifold and to prevent ambient air from entering themanifold.

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
eta! (3) is recommended. The orifice should be protected against moisture and particulate matterwith amembrane filter or moisture trap containing Drierite, silica gel, or glass wool. The airpump mustbe 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 isthen recommended to monitor the flow. The needle valve-flowmeter combination should be protected against moisture and particulate matterwith a membrane filter or moisture trap.

2.7 Thermometer. Accurateto ±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 ofmeasuring absorbance at 352 nm with an absolute accu- racy of ±1%and linear response over the range of0-1.0 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 forall absorbance determinations.

3. Reagents. 3.1 Zero air. The zero air mustbe free of contaminants which will cause a detectable response ofthe 0, analyzer or which might react with 1% BAKI. Air meeting this re- quirement maybe obtainedby: (1) passingit 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 ofwater 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 reagentgrade;-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 allreagents.

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 orbelow 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 of0.0021% 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 pHoftheBAKI solutionshould 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 ofless than 0.008 absorbance units/cm Is ob. served, theKI reagent probably contains an excessive amount ofareducing contaminant and -must be discarded.In this event, prepare fresh absorbing reagent using a differentnumbered lot of KI.If unacceptable absorbing reagent results from different lots ofHI, test the possibility ofcontamination In theHIBO, by using a dlfferen~numbered lotof HBO.

3.9 Hydrogen peroxide solution 0.0021%. Using a graduated pipet, add 0.7 ml of 30%

or7.0 ml of 3%hydrogen peroxide (11.0) to approximately 200 ml ofdistilled water in a 500-ml volumetric flask, dilute to volume with distilled water andmix thoroughly. To prepare-the 0.0021% solution, pipet 5 ml of the above solution into 50 ml of distilled water in a 100-mlvolumetric 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 oftheBAKI 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 shownin Figure 1.

4.2 Assemble theHI 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 6mm (/ 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"Cand 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

HeinOnline -- 44 Fed. Reg. 8228 1979

### RULES AND REGULATIONS

4.4 KI calibration curve. 4.4.1 Prepare iodine standards, fresh when needed,asfollows:

A. Accuratelypipet 10 ml of0.1N standard potassium iodate (KIO.)solution into a 

### 100- nlvolumetric flask containing approximately 50 ml ofdistilled water. Add 1g ofpotassium iodide (KI) and 5 ml of IN sulfuric acid (HO,), dilute to volume with distilled water,and mix thoroughly.

B. Immediately beforeuse, 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 absorbingreagent.

C. In turn, pipet 5, 10, 15. 20, and 25 ml aliquots of the final I solution prepared In stepB above into a series of 25-ml volumetric flasks. Dilute each to volume with absorbing reagent and mix thoroughly. To prevent I.losses byvolatilization, theflasks should remain stoppered until absorbance measurements are made. Absorbance measurements (see 4.4.2) shouldbetaken within 20minutes afterpreparation oftheI 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 ofeach I standard as:


### Ssarple ( 

### Iunexposed net absorbance absorbancel- reagent I S ~~rnc- 1 absorbance

4.4.3 For each I. standard, calculate the netabsorbance/cm as:

net absorbance/cm = net absorbance b

where:

b=spectrophotometer cell pathlength, cm4.4.4 For each I. standard. calculate the I.concentration inmole/liter as:

Iequivalpnt 12 1r-oc 12 C 1 2 1i V,1 0 3 x T -- equ

t a -t 10 ' 3 '

-eq valen 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,or25 ml, 4.4.5 Plot net absorbance/cm (y.axls)

versus the mole Idlter (x-axis) for each L standard anddraw theKI 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 notwithin this range, and the photometric accuracy of the spectrophotometer meetsthe specifications givenin 2.11, repeat the procedure using freshly prepared I, standards. If the slopeis stillnotwithin the specified range, repeat the procedure using

a differentlot ofcertified 0.1N KIO, to preparethe I.standards.

4.5 Calibration ofthe ozone generator. 4.5.1 Adjust the air flow through the 0, generator tothe desiredflowrate 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 flowat thevent.

4.5.2 With the 0, generator olf.flush the system with zero air for at least 15 minutes toremove residual 0. Pipet 10ml ofabsorbing 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 transferthe 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 ofthe two solutions to obtain the total net absorbance. Calculate the ldicated0, concentration (systemblink)as equiv- * alent 0, concentration according to 4.5.4. If the system blank Is greater than 0.005ppm 0,, continue flushing the O, generation system for an additional 30 minutes and re- determine the system blank.If the system blank is stillgreater than 0.005 ppm0,. 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 the0. generator to generate *an 0, concentration In therange 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 ofabsorbIng reagent into each Impinger. Draw 0. from the output manifold ofthe 0, calibratIon system through the sampling train at 0.4-0.6 lIter/mLn. Use a sample time ofbetween 10 and 30 minutes such that a total net absorbance between 0.1 and 1.0 absorbance units is obtained.(Atan 0 concentration of 0.1 ppm and a sampling rate of 0.5 liter/min. a total net absorbane >0.1 absorbanceunits shouldbe obtainedIfa sampling time of 20 minutes and 1-cm spectrophotometer cells are used.) Immediately after collection, transfer the exposed solutions' to clean spectrophotometer cells. Determine thenet absorbance (sample absorbance-unexposed reagent absorbance) of each solution at 352 nm within three minutes. Add the net absorbances ofthe two solutions to obtain the totalnet absorbance.

4.5.4 Calculation of ozone concentration. 4.5.4.1 Calculate the total volume of air. sampled, corrected to reference conditions of25*C and 760 tor" as:

VR = FR X tS 

### where: Vx=volume of air sampled, corrected to

referenceconditions,liter Fj.=sampling flowrate corrected to refer-

enceconditions,liter/min ts-=mplingtime.min 4.5.4.2 Calculate the I,released inmoles

as:

31e I = total net absorbancex 0.01 2 Scx b

where: totalnet absorbance=sum. ofnetabsorbances forthetwosolutions

0.01=volume ofabsorbing reagentin each

Impinger,liter S,=sloe of Kr calibration curve, liter

mole- 'cm b=spectrophotometer cellpathlength,cm 4.5.4.3 Calculatethe tZ of0, absorbed as:

or - e I ee0 3 24.471G 10 61.1 3 2 T-=Me-r -=-e-3 1 0



### or,

I'

### 03 ' role 12 24.47 x 106

4.5.4.4 ppmas: Calculate the 0, concentration in

P1 03 pp 0 3 = 

### 7R

4.5.5 Repeat steps 4.5.3 and 4.5.4 atleast

onemore time atthe same 0. generator setting.Average the two (or more) determinations andrecord the average along withthe 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 anddrawthe 0, generator calibration curve.

4.6 Calibration ofthe ozone analyzer. 4.6.1 Allow sufficienttimeforthe0. analyzer towarm-up andstabilize.

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. Offsettingthe analyzer's zero adjustmentto +5% of scale Is recommended to facilitate observing negative zero drift. Record the stable zeroairresponse as "Z'.

4.6.3 Usingthe 0. generator ascalibrated above and thesame P..generate an 0, con- centration near 80% of the desired upper range limitCURL) ofthe 0, analyzer.

4.6.4 Allow the 0, analyzer to sample this0, concentration until a stableresponse is obtained. Adjust the analyzer's span con- trol to obtain a convenient recorder response asindicatedbelow:

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, ppmURL= upper range limit of the 0 analyzer, ppm, Z

- recorder responsewith zero air, %scale.
Record the 0. concentration and the 0. analyzerresponse. Ifsubstantial adjustment ofthe span control isnecessary, recheck the

zero and span adjustments .by repeating steps 4.6.2through 4.6.4.

4.6.5 Generate several other O concen- trations (atleast5 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) orby 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 theappropriate response factor.

4.6.7 Option .: Thevariods 0. concentrations required in step 4.6.5 may be obtained by dilution ofthe O. concentration generated in 4.6.3. With this option, accurate flow measurements are required. The dynamic calibration system must be modified as shown inFigure 3 to allow fordilution airto be metered in downstream of the 0. generator.A mixing chamber between theO generator and the output manifold s also re- quired. The flowrate through the O generator (Fo) and the dilution air flowrate (FD)

aremeasured 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 iscalculated from:

F 0 [03]OU T = [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 the0. analyz-

er may alsobe accomplished by hssaying the
03 concentrations using the procedure in4.5 while simultaneously measuring the corre- sponding 0. analyzer responses as specified in 4.6.

REFERENCES

1. D. L.Flamm, "Analysis ofOzone atLow Concentrations with Boric Acid Buffered KI," Environ.Sci. TechnoL, 11, 978 (1977).

2. B.E.Saltzman andN. 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. ControlAssoc., 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 5ml INTERVALS. ALLTHE WAY AROUND



### II NOZZLEID EXACTLY S--j 1mm. PASSES 0.09 TO 0I 

### 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 ISA 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 ofd 

### tymcll BAKI cdlbration system (Option 1)

rFRDoe. '79-4057Filed 

### 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