1、Designation: D5110 98 (Reapproved 2010)Standard Practice forCalibration of Ozone Monitors and Certification of OzoneTransfer Standards Using Ultraviolet Photometry1This standard is issued under the fixed designation D5110; the number immediately following the designation indicates the year oforigina
2、l adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers a means for calibrating ambient,workplace, or
3、 indoor ozone monitors, and for certifyingtransfer standards to be used for that purpose.1.2 This practice describes means by which dynamicstreams of ozone in air can be designated as primary ozonestandards.1.3 The values stated in SI units are to be regarded asstandard. No other units of measuremen
4、t are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitatio
5、ns prior to use. See Section 8 forspecific precautionary statements.2. Referenced Documents2.1 ASTM Standards:2D1356 Terminology Relating to Sampling and Analysis ofAtmospheresD3195 Practice for Rotameter CalibrationD3249 Practice for General Ambient Air Analyzer Proce-duresD3631 Test Methods for Me
6、asuring Surface AtmosphericPressureD5011 Practices for Calibration of Ozone Monitors UsingTransfer Standards3E220 Test Method for Calibration of Thermocouples ByComparison TechniquesE591 Practice for Safety and Health Requirements Relatingto Occupational Exposure to Ozone3E644 Test Methods for Testi
7、ng Industrial Resistance Ther-mometers3. Terminology3.1 For definitions of terms used in this practice, refer toTerminology D1356.3.2 Definitions of Terms Specific to This Standard:3.2.1 primary standarda standard directly defined andestablished by some authority, against which all secondarystandard
8、s are compared.3.2.2 secondary standarda standard used as a means ofcomparison, but checked against a primary standard.3.2.3 standardan accepted reference sample or deviceused for establishing measurement of a physical quantity.3.2.4 transfer standarda type of secondary standard. It isa transportabl
9、e device or apparatus that, together with opera-tional procedures, is capable of reproducing pollutant concen-tration or producing acceptable assays of pollutant concentra-tions.3.2.5 zero airpurified air that does not contain ozone, anddoes not contain any other component that may interfere withthe
10、 measurement (see 7.1).4. Summary of Practice4.1 This practice is based on the photometric assay of ozone(O3) concentrations in a dynamic flow system. The concentra-tion of O3in an absorption cell is determined from a measure-ment of the amount of 253.7 nm light absorbed by the sample.This determina
11、tion requires knowledge of (1)4the absorptioncoefficient of O3at 253.7 nm, (2) the optical path lengththrough the sample, (3) the transmittance of the sample at a1This practice is under the jurisdiction ofASTM Committee D22 onAir Qualityand is the direct responsibility of Subcommittee D22.03 on Ambi
12、ent Atmospheresand Source Emissions.Current edition approved Oct. 1, 2010. Published November 2010. Originallyapproved in 1990. Last previous edition approved in 2004 as D5110 - 98(2004).DOI: 10.1520/D5110-98R10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Cus
13、tomer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.4The boldface numbers in parentheses refer to the references listed at the end ofthis practice.1Copyright ASTM International, 100 Barr Har
14、bor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.wavelength of 253.7 nm, and (4) the temperature and pressureof the sample. The transmittance is defined as the ratio:I/Iowhere:I = the intensity of light that passes through the cell and issensed by the detector when the cell co
15、ntains an O3sample, andIo= the intensity of light that passes through the cell and issensed by the detector when the cell contains zero air.It is assumed that all conditions of the system, except for thecontents of the absorption cell, are identical during measure-ments of I and Io. The quantities d
16、efined above are related bythe Beer-Lambert absorption law:Transmittance5I/Io5e2acd(1)where:a = absorption coefficient of O3at 253.7 nm,(308 6 4) 3 106ppm1cm1at 0C and 101.3 kPa (1atm) (1, 2, 3, 4, 5, 6, 7, 8)c =O3concentration, ppm, andd = optical path length, cm.4.1.1 In practice, a stable O3gener
17、ator (see 6.1.4) is used toproduce O3concentrations over the required range. Each O3concentration is determined from the measurement of thetransmittance of the sample at 253.7 nm, and is calculated fromthe equation:c52lnIIoad!(2)The calculated O3concentrations must be corrected for O3losses, which m
18、ay occur in the photometer, and for thetemperature and pressure of the sample.5. Significance and Use5.1 The reactivity and instability of O3preclude the storageof O3concentration standards for any practical length of time,and precludes direct certification of O3concentrations asStandard Reference M
19、aterials (SRMs). Moreover, there is noavailable SRM that can be readily and directly adapted to thegeneration of O3standards analogous to permeation devicesand standard gas cylinders for sulfur dioxide and nitrogenoxides. Dynamic generation of O3concentrations is relativelyeasy with a source of ultr
20、aviolet (UV) radiation. However,accurately certifying an O3concentration as a primary standardrequires assay of the concentration by a comprehensivelyspecified analytical procedure, which must be performed everytime a standard is needed (9).5.2 This practice is not designed for the routine calibrati
21、onof O3monitors at remote locations (see Practices D5011).6. Apparatus6.1 Atypical complete UV calibration system consists of anO3generator, an output port or manifold, a photometer, asource of zero air, and other components as necessary. Theconfiguration must provide a stable O3concentration at the
22、system output and allow the photometer to assay accurately theoutput concentration to the precision specified for the photom-eter. Fig. 1 shows the system, and illustrates the calibrationsystem. Ozone is highly reactive and subject to losses uponcontact with surfaces. All components between the O3ge
23、nera-tor and the photometer absorption cell shall be of inertmaterial, such as glass or TFE-fluorocarbon. Lines and inter-connections shall be as short as possible, and all surfaces shallbe chemically clean. For certification of transfer standards thatprovide their own source of O3, the generator an
24、d possiblyother components shown in Fig. 1 may not be required (seePractices D5011).6.1.1 UV Photometer, consisting of a low-pressure mercurydischarge lamp, collimation optics (optional), an absorptioncell, a detector, and signal-processing electronics, as shown inFig. 1. It shall be capable of meas
25、uring the transmittance, I/Io,at a wavelength of 253.7 nm with sufficient precision that thestandard deviation of the concentration measurements does notexceed the greater of 0.005 ppm or 3 % of the concentration. Itshall incorporate means to assure that no O3is generated in thecell by the UV lamp.
26、This is generally accomplished byabsorbing the 184.9 nm Hg line with a high silica window, orby isolating the 253.7 nm Hg line with an interference filter. Inaddition, at least 99.5 % of the radiation sensed by the detectorshall be 253.7 nm. This is usually accomplished by using asolar blind photodi
27、ode tube. The length of the light paththrough the absorption cell shall be known with an accuracy ofat least 0.5 %. In addition, the cell and associated plumbingshall be designed to minimize loss of O3from contact withsurfaces (10).6.1.2 Air Flow Controller, capable of regulating air flows asnecessa
28、ry to meet the output stability and photometer precisionrequirements.6.1.3 Flowmeters, calibrated in accordance with PracticeD3195.6.1.4 Ozone Generator, capable of generating stable levelsof O3over the required concentration range. It shall be stableover short periods to facilitate the sequential p
29、hotometricmeasurement of I and Io, and to allow for stability of themonitor or transfer standard connected to the output manifold.Conventional UV-photolytic type generators may be adequate,but shall have line voltage and temperature regulation.6.1.5 Output Manifold, constructed of glass, TFE-fluoroc
30、arbon, or other nonreactive material. It shall be ofsufficient diameter to ensure a negligible pressure drop at thephotometer connection and other output ports. The outputmanifold serves the function of providing an interface betweenthe calibration system and other devices and systems thatutilize th
31、e output O3concentrations. It shall have one or moreports for connection of the external instruments or systems, andshall be such that all ports provide the same O3concentrations.The vent, which exhausts excess gas flow from the system andinsures that the manifold outlet ports are kept at atmospheri
32、cpressure for all flowrates, shall be large enough to avoidappreciable pressure drop, and shall be located downstream ofthe output ports to ensure that no ambient air enters themanifold due to eddy currents, back diffusion, and so forth.6.1.6 Three-Way Valve, constructed of TFE-fluorocarbon, toswitc
33、h the flow through the absorption cell from zero air (forthe Iomeasurement) to manifold gas (for the I measurement).D5110 98 (2010)26.1.7 Temperature Indicator, accurate to 61C. This indi-cator is needed to measure the temperature of the gas in thephotometric cell to calculate a temperature correcti
34、on. In mostphotometers, particularly those whose cell is enclosed inside acase or housing with other electrical or electronic components,the cell operates at a temperature somewhat above ambientroom temperature. Therefore, it is important to measure thetemperature of the gas inside the cell, and not
35、 room tempera-ture. A small thermocouple or thermistor, connected to anexternal readout device, may be attached to the cell wall orinserted through the cell wall to measure internal cell tempera-ture. The point of temperature sensing shall be representativeof the average cell temperature. The temper
36、ature sensingdevice shall be calibrated against a NIST certified thermometerinitially, and at periodic intervals, subject to the laboratoryquality control checks (11). See Method E220 or Test MethodsE644 for calibration procedures.6.1.8 Barometer or Pressure Indicator, accurate to 250 Pa (2torr). Th
37、e barometer or pressure indicator is used to measurethe pressure of the gas in the cell to calculate a pressurecorrection. Most photometer cells operate at atmosphericpressure. If there are no restrictions between the cell and theoutput manifold, the cell pressure should be very nearly thesame as th
38、e local barometric pressure. A certified local baro-metric pressure reading can then be used for the pressurecorrection. If the cell pressure is different from the localbarometric pressure, some means of accurately measuring thecell pressure (manometer, pressure gauge, or pressure trans-ducer) is re
39、quired. This device shall be calibrated against asuitable pressure standard, in accordance with Test MethodsD3631.6.1.9 Output Indicating Device, such as continuous stripchart recorder or digital volt meter.6.1.9.1 If a recorder is used, it shall have the followingspecifications:Accuracy 60.25 % of
40、spanChart width no less than 150 mmTime for full-scale travel 1 s6.1.9.2 If a digital volt meter is used, it shall have anaccuracy of 60.25 % of range.7. Reagents and Materials7.1 Zero AirFree of O3and any substance that by itself orwhose decomposition products from the ozonizer might reactwith O3,
41、absorb 255.7 nm light, or undergo photolysis (forFIG. 1 Schematic Diagram of a Typical UV Photometric Calibration SystemD5110 98 (2010)3example NO, NO2, ethylene, and particulate matter). The airshall be purified to remove such substances. Dirty air shall beprecleaned to remove particulate matter, o
42、il mist, liquid water,and so forth.7.1.1 The following describes a system that has been usedsuccessfully: The air is dried with a membrane type dryer,5followed by a column of indicating silica gel. The air isirradiated with a UV lamp to generate O3, to convert NO toNO2and then passed through a colum
43、n of activated charcoal (6to 14 mesh) to remove NO2,O3, hydrocarbons, and variousother substances, a column of molecular sieve (6 to 16 mesh,type 4A), and a final particulate filter (2 m) to removeparticulate matter. (WarningAn important requirement inphotometer operation is that the zero air suppli
44、ed to thephotometer during the Iomeasurement is from the same sourceas that used for the generation of O3. The impurities present inzero air from different sources can significantly affect thetransmittance of an air sample. This requirement presents noproblem if the configuration shown in Fig. 1 is
45、used. However,there may be a problem in certifying O3generator transferstandards that have their own source of zero air or O3(seePractices D5011). The zero air produced in 7.1.1 is very dry.The O3response of some measurement methods (for example,ethylene chemiluminescence, KI bubblers) is affected b
46、ychanges in relative humidity. This dependence should be takeninto account when reporting results.)8. Hazards8.1 Safety HazardsSee Practice D3249 for safety precau-tions on the use of monitors and electronic equipment.8.1.1 Ozone is a toxic gaseous substance. See Practice E591for biological effects,
47、 and for safety and health requirements.8.1.2 The manifold vents and photometer and monitorexhausts must be vented to remove exhaust gases from theworkplace. Care shall be taken to avoid a back pressure in thecell and manifold, and in the monitor or transfer standard beingcalibrated.9. Preparation o
48、f Apparatus9.1 ConditioningThe system shall be conditioned byflowing O3at maximum concentration for 10 to 30 mininitially, and after periods of time while the system was notused, prior to reuse.9.2 General OperationA photometer used as a primarystandard shall be dedicated exclusively to calibration
49、serviceand specifically not used for ambient monitoring or as atransfer standard. The reason for this requirement is that thephotometer must be intrinsically accurate and not exposed tooutside effects. If it is used for other purposes, it will eventuallybecome dirty and will be prone to O3losses and will giveerratic readings. Reserving the photometer for use as a primarystandard, where only clean, dry, filtered gas passes through thecell, will minimize loss of accuracy. A photometer used as atransfer standard will be subjected to environmental condi-tions, which may
