ASTM D5110-98

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D 5110 – 98
Standard Practice for
Calibration of Ozone Monitors and Certification of Ozone
1,2
Transfer Standards Using Ultraviolet Photometry
This standard is issued under the fixed designation D 5110; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This practice covers a means for calibrating ambient, 3.1 For definitions of terms used in this practice, refer to
workplace, or indoor ozone monitors, and for certifying Terminology D1356.
transfer standards to be used for that purpose. 3.2 Definitions of Terms Specific to This Standard:
1.2 This practice describes means by which dynamic 3.2.1 primary standard—a standard directly defined and
streams of ozone in air can be designated as primary ozone established by some authority, against which all secondary
standards. standards are compared.
1.3 This standard does not purport to address all of the 3.2.2 secondary standard—a standard used as a means of
safety concerns, if any, associated with its use. It is the comparison, but checked against a primary standard.
responsibility of the user of this standard to establish appro- 3.2.3 standard—an accepted reference sample or device
priate safety and health practices and determine the applica- used for establishing measurement of a physical quantity.
bility of regulatory limitations prior to use. See Section 8 for 3.2.4 transfer standard—a type of secondary standard. It is
specific precautionary statements. a transportable device or apparatus that, together with opera-
tional procedures, is capable of reproducing pollutant concen-
2. Referenced Documents
tration or producing acceptable assays of pollutant concentra-
2.1 ASTM Standards:
tions.
D1356 Terminology Relating to Sampling andAnalysis of 3.2.5 zero air—purified air that does not contain ozone, and
Atmospheres
does not contain any other component that may interfere with
D3195 Practice for Rotameter Calibration the measurement (see 7.1).
D3249 Practice for General Ambient Air Analyzer Proce-
4. Summary of Practice
dures
D3631 Test Methods for Measuring Surface Atmospheric 4.1 Thispracticeisbasedonthephotometricassayofozone
Pressure (O ) concentrations in a dynamic flow system. The concentra-
D5011 Practices for Calibration of Ozone Monitors Using tion of O in an absorption cell is determined from a measure-
Transfer Standards ment of the amount of 253.7 nm light absorbed by the sample.
E220 Method for Calibration of Thermocouples By Com- This determination requires knowledge of (1) the absorption
parison Techniques coefficient of O at 253.7 nm, (2) the optical path length
E591 PracticeforSafetyandHealthRequirementsRelating through the sample, (3) the transmittance of the sample at a
to Occupational Exposure to Ozone wavelength of 253.7 nm, and (4) the temperature and pressure
E644 Test Methods for Testing Industrial Resistance Ther- of the sample. The transmittance is defined as the ratio:
mometers
I/I
o
where:
This practice is under the jurisdiction ofASTM Committee D-22 on Sampling
I = theintensityoflightthatpassesthroughthecellandis
and Analysis of Atmospheres, and is the direct responsibility of Subcommittee
sensed by the detector when the cell contains an O
D22.03 on Ambient Atmospheres and Source Emissions.
sample, and
Current edition approved Oct. 10, 1998. Published December 1998. Originally
published as D5110–90. Last previous edition D5110–94. I = theintensityoflightthatpassesthroughthecellandis
o
This practice is adapted from EPA-600/4-79-057, September 1979; “Technical
sensed by the detector when the cell contains zero air.
Assistance Document for the Calibration of Ambient Ozone Monitors”, by R.J.
Itisassumedthatallconditionsofthesystem,exceptforthe
Paur and F.F. McElroy.Available from the NationalTechnical Information Service,
contents of the absorption cell, are identical during measure-
Springfield, VA 22161.
Annual Book of ASTM Standards, Vol 11.03.
ments of I and I . The quantities defined above are related by
o
Discontinued; see 1994 Annual Book of ASTM Standards, Vol 14.03.
the Beer-Lambert absorption law:
Discontinued; see 1990 Annual Book of ASTM Standards, Vol 11.03.
Annual Book of ASTM Standards, Vol 14.03.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D5110
2acd
6.1.1 UV Photometer, consisting of a low-pressure mercury
Transmittance5I/I 5e (1)
o
discharge lamp, collimation optics (optional), an absorption
where:
cell, a detector, and signal-processing electronics, as shown in
a = absorption coefficient of O at 253.7 nm,
Fig. 1. It shall be capable of measuring the transmittance, I/I ,
o
−6 −1 −1
(308 64) 310 ppm cm at 0°C and 101.3 kPa (1
at a wavelength of 253.7 nm with sufficient precision that the
atm) (1, 2, 3, 4, 5, 6, 7, 8)
standarddeviationoftheconcentrationmeasurementsdoesnot
c =O concentration, ppm, and
exceedthegreaterof0.005ppmor3%oftheconcentration.It
d = optical path length, cm.
shallincorporatemeanstoassurethatnoO isgeneratedinthe
4.1.1 In practice, a stable O generator (see 6.1.4) is used to
cell by the UV lamp. This is generally accomplished by
produce O concentrations over the required range. Each O
3 3
absorbing the 184.9 nm Hg line with a high silica window, or
concentration is determined from the measurement of the
by isolating the 253.7 nmHg line with an interference filter. In
transmittanceofthesampleat253.7nm,andiscalculatedfrom
addition,atleast99.5%oftheradiationsensedbythedetector
the equation:
shall be 253.7 nm. This is usually accomplished by using a
I
solar blind photodiode tube. The length of the light path
2ln
I
o
throughtheabsorptioncellshallbeknownwithanaccuracyof
c5 (2)
~ad!
at least 0.5%. In addition, the cell and associated plumbing
The calculated O concentrations must be corrected for O shall be designed to minimize loss of O from contact with
3 3 3
losses, which may occur in the photometer, and for the surfaces (10).
temperature and pressure of the sample.
6.1.2 Air Flow Controller, capable of regulating air flows as
necessarytomeettheoutputstabilityandphotometerprecision
5. Significance and Use
requirements.
5.1 The reactivity and instability of O preclude the storage 6.1.3 Flowmeters, calibrated in accordance with Practice
of O concentration standards for any practical length of time, D3195.
and precludes direct certification of O concentrations as
3 6.1.4 Ozone Generator, capable of generating stable levels
Standard Reference Materials (SRM’s). Moreover, there is no
of O over the required concentration range. It shall be stable
available SRM that can be readily and directly adapted to the
over short periods to facilitate the sequential photometric
generation of O standards analogous to permeation devices
measurement of I and I , and to allow for stability of the
o
and standard gas cylinders for sulfur dioxide and nitrogen
monitor or transfer standard connected to the output manifold.
oxides. Dynamic generation of O concentrations is relatively
Conventional UV-photolytic type generators may be adequate,
easy with a source of ultraviolet (UV) radiation. However,
but shall have line voltage and temperature regulation.
accuratelycertifyinganO concentrationasaprimarystandard
6.1.5 Output Manifold, constructed of glass, TFE-
requires assay of the concentration by a comprehensively
fluorocarbon, or other nonreactive material. It shall be of
specifiedanalyticalprocedure,whichmustbeperformedevery
sufficient diameter to ensure a negligible pressure drop at the
time a standard is needed (9).
photometer connection and other output ports. The output
5.2 This practice is not designed for the routine calibration
manifoldservesthefunctionofprovidinganinterfacebetween
of O monitors at remote locations (see Practices D5011).
the calibration system and other devices and systems that
utilize the output O concentrations. It shall have one or more
6. Apparatus
portsforconnectionoftheexternalinstrumentsorsystems,and
6.1 AtypicalcompleteUVcalibrationsystemconsistsofan
shallbesuchthatallportsprovidethesameO concentrations.
O generator, an output port or manifold, a photometer, a
The vent, which exhausts excess gas flow from the system and
source of zero air, and other components as necessary. The
insures that the manifold outlet ports are kept at atmospheric
configuration must provide a stable O concentration at the
pressure for all flowrates, shall be large enough to avoid
systemoutputandallowthephotometertoassayaccuratelythe
appreciable pressure drop, and shall be located downstream of
output concentration to the precision specified for the photom-
the output ports to ensure that no ambient air enters the
eter. Fig. 1 shows the system, and illustrates the calibration
manifold due to eddy currents, back diffusion, and so forth.
system. Ozone is highly reactive and subject to losses upon
6.1.6 Three-Way Valve, constructed ofTFE-fluorocarbon, to
contact with surfaces.All components between the O genera-
3 switch the flow through the absorption cell from zero air (for
tor and the photometer absorption cell shall be of inert
the I measurement) to manifold gas (for the I measurement).
o
material, such as glass or TFE-fluorocarbon. Lines and inter-
6.1.7 Temperature Indicator, accurate to 61°C. This indi-
connections shall be as short as possible, and all surfaces shall
cator is needed to measure the temperature of the gas in the
be chemically clean. For certification of transfer standards that
photometric cell to calculate a temperature correction. In most
provide their own source of O , the generator and possibly
photometers, particularly those whose cell is enclosed inside a
other components shown in Fig. 1 may not be required (see
case or housing with other electrical or electronic components,
Practices D5011).
the cell operates at a temperature somewhat above ambient
room temperature. Therefore, it is important to measure the
temperature of the gas inside the cell, and not room tempera-
ture. A small thermocouple or thermistor, connected to an
The boldface numbers in parentheses refer to the references listed at the end of
this practice. external readout device, may be attached to the cell wall or
D5110
FIG. 1 Schematic Diagram of a Typical UV Photometric Calibration System
inserted through the cell wall to measure internal cell tempera- ducer) is required. This device shall be calibrated against a
ture. The point of temperature sensing shall be representative suitable pressure standard, in accordance with Test Methods
D3631.
of the average cell temperature. The temperature sensing
6.1.9 Output Indicating Device, such as continuous strip
deviceshallbecalibratedagainstaNISTcertifiedthermometer
chart recorder or digital volt meter.
initially, and at periodic intervals, subject to the laboratory
6.1.9.1 If a recorder is used, it shall have the following
qualitycontrolchecks(11).SeeMethodE220orTestMethods
specifications:
E644 for calibration procedures.
Accuracy 60.25 % of span
6.1.8 Barometer or Pressure Indicator,accurateto250Pa(2
Chart width no less than 150 mm
torr). The barometer or pressure indicator is used to measure
Time for full-scale travel 1 s
the pressure of the gas in the cell to calculate a pressure
correction. Most photometer cells operate at atmospheric
6.1.9.2 If a digital volt meter is used, it shall have an
pressure. If there are no restrictions between the cell and the
accuracy of 60.25% of range.
output manifold, the cell pressure should be very nearly the
7. Reagents and Materials
same as the local barometric pressure. A certified local baro-
metric pressure reading can then be used for the pressure
7.1 Zero Air—FreeofO andanysubstancethatbyitselfor
correction. If the cell pressure is different from the local whose decomposition products from the ozonizer might react
barometric pressure, some means of accurately measuring the with O , absorb 255.7 nm light, or undergo photolysis (for
cell pressure (manometer, pressure gauge, or pressure trans- example NO, NO , ethylene, and particulate matter). The air
D5110
shall be purified to remove such substances. Dirty air shall be 9.3 Photometer Verifications—Since the accuracy of the
precleaned to remove particulate matter, oil mist, liquid water, calibrationstandardsobtainedbythispracticedependsentirely
and so forth.
ontheaccuracyofthephotometer,itisimportanttoensurethat
7.1.1 The following describes a system that has been used the photometer is operating properly and accurately.
successfully: The air is dried with a membrane type dryer,
9.3.1 A well designed and properly built photometer is a
followed by a column of indicating silica gel. The air is
precision instrument; once shown to operate adequately, it is
irradiated with a UV lamp to generate O , to convert NO to
likely to continue to do so for some time, particularly if it is
NO andthenpassedthroughacolumnofactivatedcharcoal(6
held stationary and used intermittently under laboratory con-
to 14 mesh) to remove NO,O , hydrocarbons, and various
2 3
ditions.Therefore,theperformancechecksmaynotnecessarily
other substances, a column of molecular sieve (6 to 16 mesh,
have to be conducted every time the photometer is used. The
type 4A), and a final particulate filter (2 µm) to remove
actual frequency of the checks is a trade-off between confi-
particulate matter.
denceinthephotometerperformanceandthecostandeffortto
conductthechecks.Thisisamatterofjudgment,subjecttothe
NOTE 1—Caution:—An important requirement in photometer opera-
tion is that the zero air supplied to the photometer during the I
laboratory quality control checks (11). One reasonable ap-
o
measurementisfromthesamesourceasthatusedforthegenerationofO .
proach is to perform the checks very frequently with a new
The impurities present in zero air from different sources can significantly
photometer, keeping a chronological record of each perfor-
affect the transmittance of an air sample. This requirement presents no
mance check, using the QA control chart, and to reduce the
problem if the configuration shown in Fig. 1 is used. However, there may
frequencyasexperiencedictates.Evenwheretherecordshows
be a problem in certifying O generator transfer standards that have their
ownsourceofzeroairorO (seePracticesD5011).Thezeroairproduced excellent stability, the checks shall be performed at some
in 7.1.1 is very dry.
...