ASTM D5156-22

Standard Test Methods for Continuous Measurement of Ozone in Ambient, Workplace, and Indoor Atmospheres (Ultraviolet Absorption)

SIGNIFICANCE AND USE
5.1 Standards for O3  in the atmosphere have been promulgated by government authorities to protect the health and welfare of the public (6) and also for the protection of industrial workers (7).  
5.2 Although O3  itself is a toxic material, in ambient air it is primarily the photochemical oxidants formed along with O3  in polluted air exposed to sunlight that cause smog symptoms such as lachrymation and burning eyes. Ozone is much more easily monitored than these photochemical oxidants and provides a good indication of their concentrations, and it is therefore the substance that is specified in air quality standards and regulations.
SCOPE
1.1 This test method describes the sampling and continuous analysis of ozone (O3) in the atmosphere at concentrations ranging from 10 to 2000 μg/m3 of O3  in air (5 ppb(v) to 1 ppm(v)).  
1.1.1 The test method is limited to applications by its sensitivity to interferences as described in Section 6. The interference sensitivities may limit its use for ambient and workplace atmospheres.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Aug-2022
• ICS: 13.040.30 - Workplace atmospheres
• Technical Committee: D22 - Air Quality
• Drafting Committee: D22.03 - Ambient Atmospheres and Source Emissions

Relations

• Refers: ASTM D1356-20a - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-Sep-2020
• Refers: ASTM D1356-20 - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 15-Mar-2020
• Refers: ASTM D3249-95(2019) - Standard Practice for General Ambient Air Analyzer Procedures
• Effective Date: 01-Oct-2019
• Refers: ASTM D1357-95(2019) - Standard Practice for Planning the Sampling of the Ambient Atmosphere
• Effective Date: 01-Aug-2019
• Refers: ASTM D5011-17 - Standard Practices for Calibration of Ozone Monitors Using Transfer Standards
• Effective Date: 01-Oct-2017
• Refers: ASTM D3631-99(2017) - Standard Test Methods for Measuring Surface Atmospheric Pressure
• Effective Date: 01-Mar-2017
• Refers: ASTM D1356-15a - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 15-Oct-2015
• Refers: ASTM D1356-15 - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-Jul-2015
• Refers: ASTM D1356-14b - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-Dec-2014
• Refers: ASTM D1356-14a - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-May-2014
• Refers: ASTM D1356-14 - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 15-Jan-2014
• Refers: ASTM D3631-99(2011) - Standard Test Methods for Measuring Surface Atmospheric Pressure
• Effective Date: 01-Oct-2011
• Refers: ASTM D3249-95(2011) - Standard Practice for General Ambient Air Analyzer Procedures
• Effective Date: 01-Oct-2011
• Refers: ASTM D1357-95(2011) - Standard Practice for Planning the Sampling of the Ambient Atmosphere
• Effective Date: 01-Oct-2011
• Refers: ASTM D5110-98(2010) - Standard Practice for Calibration of Ozone Monitors and Certification of Ozone Transfer Standards Using Ultraviolet Photometry
• Effective Date: 01-Oct-2010

Overview

ASTM D5156-22 establishes standard test methods for the continuous measurement of ozone (O₃) concentrations in ambient, workplace, and indoor atmospheres using ultraviolet (UV) absorption. This standard, developed by ASTM International, plays a crucial role in air quality monitoring to safeguard public health and the welfare of workers. Ozone is both an environmental and occupational concern due to its role as a photochemical oxidant and its direct toxicity. Continuous ozone monitoring, as provided by this standard, is vital for regulatory compliance and effective air quality management in various environments.

Key Topics

• Ozone Measurement Principle: The standard specifies the use of ultraviolet absorption at a wavelength of 253.7 nm for detecting ozone in air. This method leverages the Beer-Lambert law, allowing accurate quantification over a range of 5 ppb to 1 ppm (10 to 2000 μg/m³).
• Sampling Methods: Guidance is provided for the proper sampling of air to avoid contamination and minimize interferences, including recommendations for PTFE (polytetrafluoroethylene) sampling lines and particulate filters.
• Instrument Components: Minimum requirements for photometric ozone monitors are outlined, including ultraviolet absorption cells, low-pressure mercury vapor lamps, PTFE solenoid valves, ozone-specific scrubbers (typically manganese dioxide or heated silver), vacuum photodiodes, air pumps, and signal processing electronics.
• Interferences: The method’s sensitivity to interferences is discussed. Potential interferences from aerosols, organic vapors (e.g., styrene), sulfur dioxide, nitrogen dioxide, and water vapor are specifically noted, with guidance on mitigation.
• Calibration and Maintenance: Detailed practices for calibrating ozone monitors using primary and transfer standards (in accordance with referenced ASTM practices) are required to ensure accurate and reliable results.

Applications

• Ambient Air Quality Monitoring: Used by environmental agencies to comply with national and regional air quality standards and regulations. Ozone serves as an indicator for smog and photochemical oxidants, which can have significant health effects.
• Workplace Exposure Assessment: Industrial hygienists and safety professionals use this method to monitor and control workplace ozone exposures, protecting workers from acute and chronic health risks.
• Indoor Air Quality Studies: The method facilitates studies and ongoing monitoring in office buildings, medical facilities, and other indoor spaces where ozone generation may occur (e.g., from office equipment or disinfection processes).
• Regulatory Compliance: Supports compliance with laws and standards such as the Clean Air Act, OSHA guidelines, and other occupational exposure limits set by authorities like ACGIH.

Related Standards

• ASTM D1356 - Terminology Relating to Sampling and Analysis of Atmospheres
• ASTM D1357 - Practice for Planning the Sampling of the Ambient Atmosphere
• ASTM D1914 - Practice for Conversion Units and Factors Relating to Sampling and Analysis of Atmospheres
• ASTM D3249 - Practice for General Ambient Air Analyzer Procedures
• ASTM D3631 - Test Methods for Measuring Surface Atmospheric Pressure
• ASTM D5011 - Practices for Calibration of Ozone Monitors Using Transfer Standards
• ASTM D5110 - Practice for Calibration of Ozone Monitors and Certification of Ozone Transfer Standards Using Ultraviolet Photometry
• IEEE/ASTM SI-10 - Practice for Use of the International System of Units (SI)

Practical Value

Implementing ASTM D5156-22 standardizes the continuous measurement of ozone, ensuring the data is accurate, reliable, and comparable across different sites and studies. Users benefit from:

• Improved public and occupational health protection
• Compliance with legal and regulatory requirements
• Consistency in air quality monitoring practices
• Enhanced decision-making for air pollution control and mitigation

By adhering to this internationally recognized test method, organizations demonstrate their commitment to maintaining healthy environments and meeting global standards in air quality monitoring.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D5156 − 22
Standard Test Methods for
Continuous Measurement of Ozone in Ambient, Workplace,
and Indoor Atmospheres (Ultraviolet Absorption)
This standard is issued under the fixed designation D5156; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope D3249Practice for General Ambient Air Analyzer Proce-
dures
1.1 This test method describes the sampling and continuous
D3631Test Methods for Measuring Surface Atmospheric
analysis of ozone (O ) in the atmosphere at concentrations
3 Pressure
ranging from 10 to 2000 µg/m of O in air (5 ppb(v) to
D3670Guide for Determination of Precision and Bias of
1ppm(v)).
Methods of Committee D22
1.1.1 The test method is limited to applications by its
D5011Practices for Calibration of Ozone Monitors Using
sensitivity to interferences as described in Section 6. The
Transfer Standards
interference sensitivities may limit its use for ambient and
D5110Practice for Calibration of Ozone Monitors and
workplace atmospheres.
CertificationofOzoneTransferStandardsUsingUltravio-
1.2 The values stated in SI units are to be regarded as
let Photometry
standard. No other units of measurement are included in this
IEEE/ASTM SI-10Practice for Use of the International
standard.
System of Units (SI) (the Modernized Metric System)
1.3 This standard does not purport to address all of the
2.2 Other Documents:
safety concerns, if any, associated with its use. It is the
EPA-600/4-76-005 Quality Assurance Handbook for Air
responsibility of the user of this standard to establish appro-
Pollution Measurement Systems, Vol I, “Principles”
priate safety, health, and environmental practices and deter-
EPA-600/4-77-027a Quality Assurance Handbook for Air
mine the applicability of regulatory limitations prior to use.
Pollution Measurement Systems, Vol II, “Ambient Air
1.4 This international standard was developed in accor- 3
Specific Methods”
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
3. Terminology
Development of International Standards, Guides and Recom-
3.1 Definitions—For definitions of terms used in this test
mendations issued by the World Trade Organization Technical
method, refer to Terminology D1356.An explanation of units,
Barriers to Trade (TBT) Committee.
symbols, and conversion factors may be found in Practice
IEEE/ASTM SI-10.
2. Referenced Documents
3.2 Definitions of Terms Specific to This Standard:
2.1 ASTM Standards:
3.2.1 absolute ultraviolet photometer—a photometer whose
D1356Terminology Relating to Sampling and Analysis of
design, construction, and maintenance is such that it can
Atmospheres
measure the absorbance caused by O mixtures without refer-
D1357Practice for Planning the Sampling of the Ambient
ence to external absorption standards. Given a value for the
Atmosphere
absorptioncoefficientofO at253.7nmandareadingfromthe
D1914PracticeforConversionUnitsandFactorsRelatingto
absolute ultraviolet photometer, O concentrations can be
Sampling and Analysis of Atmospheres
calculatedwithaccuracy.Anabsoluteultravioletphotometeris
used only on prepared O mixtures free from interferences, as
in calibration activity.
These test methods are under the jurisdiction ofASTM Committee D22 on Air
Quality and is the direct responsibility of Subcommittee D22.03 on Ambient
3.2.2 primary standard—a standard directly defined and
Atmospheres and Source Emissions.
established by some authority, against which all secondary
Current edition approved Sept. 1, 2022. Published September 2022. Originally
standards are compared.
approved in 1991. Last previous edition approved in 2016 as D5156–02 (2016).
DOI: 10.1520/D5156-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available from NationalTechnical Information Service (NTIS), 5301 Shawnee
the ASTM website. Rd., Alexandria, VA 22312, http://www.ntis.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5156 − 22
3.2.3 secondary standard—a standard used as a means of 4.6 At 5 ppb (v) with a 50-cm path length, the absorption is
−6 −5 4
comparison, but checked against a primary standard. 304.39×0.005×50×10 or×10 (1-5).
3.2.4 standard—an accepted reference sample or device
4.7 The instrument is calibrated by methods given in Prac-
used for establishing the measurement of a physical quantity.
tices D5011 and D5110, which describe the use of an absolute
ultraviolet photometer as a primary standard and the qualifi-
3.2.5 transfer standard—a type of secondary standard; it is
cation and use of transfer standards.
a transportable device or apparatus that, together with opera-
tional procedures, is capable of reproducing pollutant concen-
5. Significance and Use
trations or producing acceptable assays of pollutant concentra-
5.1 Standards for O in the atmosphere have been promul-
tions.
gated by government authorities to protect the health and
4. Summary of Test Method
welfare of the public (6) and also for the protection of
industrial workers (7).
4.1 Thistestmethodisbasedontheabsorptionofultraviolet
radiation at 253.7-nm wavelength by O and the use of an
5.2 AlthoughO itselfisatoxicmaterial,inambientairitis
ozone-specific scrubber to generate a reference air stream with
primarily the photochemical oxidants formed along with O in
only O scrubbed from it. A single-cell ultraviolet absorption
polluted air exposed to sunlight that cause smog symptoms
photometerisused,withthecellfilledalternatelywithambient
such as lachrymation and burning eyes. Ozone is much more
andO -scrubbedambientair.Theabsorptiontobemeasuredat
easily monitored than these photochemical oxidants and pro-
the lower part of the operating range is extremely small.
vides a good indication of their concentrations, and it is
Special precautions and designs must be used to obtain
therefore the substance that is specified in air quality standards
accurate results.
and regulations.
4.2 The absorption of radiation at 253.7 nm by O at very
6. Interferences
lowconcentrationsfollowstheBeer-LambertLaw.Namely,for
a cell of length d, assuming a constant input ultraviolet 6.1 Any aerosol or gas that absorbs or scatters ultraviolet
radiation at 253.7 nm, and that is removed by the O -specific
intensity, the ratio of the emerging intensities for the cell filled
with sample air, I , and with O -scrubbed air, I , is: scrubber, constitutes an interferent (8) to this test method (9).
s 3 o
Particulate matter can be removed with a poly-
I
s
2 cad
~ !
5 e (1)
tetrafluoroethylene (PTFE) membrane filter. Any type of filter
I
o
can, however, become contaminated and may then scrub O.It
where:
is important to check the O -inertness of such devices fre-
quently.
c = the concentration of O , ppm (v),
d = the length of the cell, cm, and
6.2 Some reported positively interfering organic species for
a = the absorption coefficient of O per length unit of d and
a manganese dioxide scrubber are tabulated in Annex A2 of
per concentration unit of c.
this test method. In general, if interferences are suspected, it is
4.3 When (cad) is << 1, as is the case for O at 253.7 nm in
preferabletouseanothertestmethodratherthantotrytoscrub
the concentration range specified for this test method, the
out the interfering agent, since the instability of O makes the
approximation
testing and proving of additional interferant scrubbers particu-
2x
larly difficult.
e ' 1 2 x (2)
~ !
6.3 Water vapor may constitute either a positive or negative
can be used to simplify the signal processing electronics, so
interferant in instruments calibrated with dry span gas (10-13).
that
6.3.1 Improperly polished absorption cell windows may
I 'I 1 2 cad (3)
~ !
s o
lead to increased signal noise and apparent ozone increases in
instruments subject to rapidly changing humidity, such as at a
and thus
coastal site where instruments may be exposed to frequent
I 2 I
~ !
o s
shifts between relatively dry terrestrial and moist oceanic air
c' (4)
I ad
o
parcels (9).
4.4 At 1 ppm (v), the high end of the recommended range,
6.3.2 A negative water vapor interference, due to humidity
andapathlengthof50cm,theerrorresultingfromapplication
dependent changes in elution rates of interferences from the
of the above approximation is approximately 1 part in 10000.
ozone scrubber may develop in manganese dioxide scrubbers
exposed to ambient air (11, 13, 14). This phenomenon is
4.5 Thus, the concentration of O can be obtained from the
described in 7.2.6.
difference between the signal from the photosensor (often a
vacuum photodiode) when the contents of the absorption cell
containsampleairfromwhichO hasbeenscrubbed,andwhen 4
3 Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
it contains sample air containing O . this test method.
D5156 − 22
7. Apparatus of the sampling cycle, of the same order as the stability
demanded of the ultraviolet source. Temperature stabilization
7.1 Instruments are commercially available that meet the
and a well-regulated photosensor supply voltage shall be
specifications provided in Annex A1. Note that these specifi-
provided to achieve the necessary stability (Fig. 1(E)).
cations do not cover operation where the ambient temperature
7.2.5 Three-Way PTFE Solenoid Valve, constructed with
changes rapidly.
internal parts of, or coated with, PTFE fluorocarbon or other
7.2 Theelementsofthetypicalozone-measuringsystemare
material that will not catalyze the destruction of O , to route
shown in Fig. 1.Assembled, they form a photometric ultravio-
thesamplethroughortobypasstheO selectivescrubber(Fig.
let monitor with specifications conforming to those listed in
1(C)).
Annex A1. The components are described in 7.2.1 – 7.2.8.
7.2.6 Ozone-Specific Scrubber, containing a material that
7.2.1 Ultraviolet Absorption Cell, constructed of materials
selectively catalyzes the destruction of O without altering or
inerttoO ,forexample,PTFE-coatedmetal,borosilicateglass,
addinganyothercompound.Manganesedioxideonasubstrate
and fused silica. It shall be mechanically stable so that the
and heated silver wool have been found generally to perform
optical alignments of the source, sensor, and any beam-
this function. However, several aromatic organic compounds
directingdevices(mirror,prisms,orlenses)arenotaffectedby
identified in Annex A2 have been shown to be adsorbed by
changes in ambient temperature (Fig. 1(F)).
manganesedioxide.Somecompoundsmaybeadsorbedpartly,
7.2.2 Ultraviolet Lamp—Alow-pressuremercuryvapordis-
producing at first an apparent higher concentration of O ,
charge lamp enclosed in a shield to prevent its radiation at
followed by a falsely lower concentration as the material is
185nm(whichgeneratesO )fromreachingtheabsorptioncell
desorbed (11). Mean O values are not affected by reversibly
(Fig. 1(J)).
adsorbed species when averaging times are much longer than
7.2.2.1 The lamp output at 253.7 nm shall be extremely
that of the absorption-desorption cycle, provided that the
stable,orprovisionshallbemadetocompensateforshort-term
possible“negative”O valuesthatresultfromthedesorptionof
variations at 253.7-nm output, for example, by the use of a
the interferant while actual O values are very low or zero are
lamp-intensity monitor to measure output from the lamp and
included in the mean. This may not be true where hourly
withelectronicstoadjustthesignalfromtheultravioletsensors
averages are calculated by simple arithmetical averaging of
correspondingly.
instantaneous values taken within a 1-h period, or where the
7.2.2.2 Shield, constructed of high-silica glass to remove
instrument contains a zero clamp that prevents negative values
the 185-nm line and permit the transmission at 253.7-nm
from being output (Fig. 1(D)). After exposure to ambient air,
radiation (Fig. 1(H)).
somemanganesedioxideozonescrubbersmaydevelopanoma-
7.2.3 Particulate Filter, installed in the sample line to
lous sensitivity to water vapor. Since such anomalous scrub-
prevent aerosols or particulate matter from entering the mea-
bers regain normality at low humidity, their anomalous behav-
suring system. PTFE fluorocarbon filters with pore sizes
ior can not be detected during span gas calibrations using dry
between 0.2 and 5.0 µm shall be used. The filter shall be
zero air. Scrubber effıciency tests must be conducted with wet
replaced frequently since accumulated materials on the filter
span gas to identify such anomalous manganese dioxide
may catalyze the breakdown of O into oxygen (Fig. 1(B)).
cartridges (15, 16).
7.2.4 Sensor—Vacuum photodiodes with cesium telluride
7.2.7 Pump—A small air pump to pull the sample air
photocathode sensitivity at 253.7-nm radiation and negligible
through the instrument (Fig. 1(N)).
sensitivity to the other mercury lamp lines. The response at
7.2.8 Flowmeter, to verify that air is moving through the
253.7 nm shall be extremely stable over the short-term periods
instrument (Fig. 1(L)).
7.3 InternalLinesandFittings,inthesamplestreampriorto
“Vycor” brand material has been found to be satisfactory.
the adsorption cell and the scrubber, constructed of PTFE
fluorocarbon or other O -inert material.
7.4 Signal Processing Electronics, containing several dis-
tinct elements (Fig. 1(K)):
7.4.1 Circuits to condition the signal from the ultraviolet-
sensitive sensor (diode) with short-term stability.
7.4.2 Timingandcontrolcircuitstooperatetheflowswitch-
ing valves and different phases of the signal conditioning
circuits.
7.4.3 Circuitstogeneratemeanvaluesfromthesignalsfrom
the sensor (diode) interface circuits for the two parts of the
cycle, to subtract them, and to output the resultant differences
in a scaled form. The circuits shall also compensate for
temperature and pressure so that the adsorption measured is
proportional to the gas density in the absorption cell.
7.4.4 TheconcentrationofO canbeobtainedfromtheratio
of the sensor (diode) signals when the adsorption cell contains
FIG. 1 Schematic Diagram of a Typical Ultraviolet Photometer sample air from which O has been scrubbed, to when it
D5156 − 22
containssampleaircontainingO .Theconversionofthisvalue 9.5 Measure and record the ambient temperature and pres-
to parts per million by volume shall include correction for sure during sampling.
ambient temperature and barometric pressure according to the
ideal gas law. The correction can be ignored if errors as great 10. Calibration and Standardization
as 65% are acceptable. Some commercially available instru-
10.1 The calibration of O monitors and the certification of
ments correct automatically for actual measurement tempera-
transfer standards using an absolute ultraviolet photometer are
ture and pressure in their concentration outputs.
described in Practice D5110 (18, 19). The use of transfer
7.4.5 Signal processing shall not prevent the output of
standards thus certified is described in Practices D5011 (20).
negativevalues,whichmayarisefrominstrumentmalfunction,
from random fluctuations in measurements of I and I in the
s o
11. Procedure and Maintenance
absenceofO ,andfrominterferencesbeingdesorbedfromthe
O -selective scrubber. 11.1 Site the monitor with consideration of Practice D1357
and other applicable documents (for example, EPA-600/4-77-
7.5 Ports,includedintheinstrumentattheentryandexitof
027a) (21).
the adsorption cell. These are helpful in determining whether
O is being destroyed in the cell.The calibration method given 11.2 Sample the atmosphere with a probe having nonreac-
in Practice D5110 describes how the ports are used.
tive inside walls such as PTFE fluorocarbon or glass. Keep the
probecleanandleak-testitmonthly.Sincethesampleflowinto
7.6 Barometer, to measure and record atmospheric pressure
theinstrumentshouldbekeptfreeofparticulatematter,change
during sampling, in accordance with Test Methods D3631.
the PTFE fluorocarbon filter used to achieve this frequently,
7.7 Temperature Measuring Equipment, to measure and
dependingontheareabeingmonitored.Eachmonth,checkthe
record ambient temperature during sampling.
degree to which the concentrati
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D5156 − 02 (Reapproved 2016) D5156 − 22
Standard Test Methods for
Continuous Measurement of Ozone in Ambient, Workplace,
and Indoor Atmospheres (Ultraviolet Absorption)
This standard is issued under the fixed designation D5156; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method describes the sampling and continuous analysis of ozone (O ) in the atmosphere at concentrations ranging
from 10 to 2000 μg/m of O in air (5 ppb(v) to 1 ppm(v)). 1 ppm(v)).
1.1.1 The test method is limited to applications by its sensitivity to interferences as described in Section 6. The interference
sensitivities may limit its use for ambient and workplace atmospheres.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D1356 Terminology Relating to Sampling and Analysis of Atmospheres
D1357 Practice for Planning the Sampling of the Ambient Atmosphere
D1914 Practice for Conversion Units and Factors Relating to Sampling and Analysis of Atmospheres
D3249 Practice for General Ambient Air Analyzer Procedures
D3631 Test Methods for Measuring Surface Atmospheric Pressure
D3670 Guide for Determination of Precision and Bias of Methods of Committee D22
D5011 Practices for Calibration of Ozone Monitors Using Transfer Standards
D5110 Practice for Calibration of Ozone Monitors and Certification of Ozone Transfer Standards Using Ultraviolet Photometry
IEEE/ASTM SI-10 Practice for Use of the International System of Units (SI) (the Modernized Metric System)
2.2 Other Documents:
EPA-600/4-76-005 Quality Assurance Handbook for Air Pollution Measurement Systems, Vol I, “Principles”
These test methods are under the jurisdiction of ASTM Committee D22 on Air Quality and is the direct responsibility of Subcommittee D22.03 on Ambient Atmospheres
and Source Emissions.
Current edition approved Oct. 1, 2016Sept. 1, 2022. Published October 2016September 2022. Originally approved in 1991. Last previous edition approved in 20082016
as D5156 – 02 (2008).(2016). DOI: 10.1520/D5156-02R16.10.1520/D5156-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from National Technical Information Service (NTIS), 5301 Shawnee Rd., Alexandria, VA 22312, http://www.ntis.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5156 − 22
EPA-600/4-77-027a Quality Assurance Handbook for Air Pollution Measurement Systems, Vol II, “Ambient Air Specific
Methods”
3. Terminology
3.1 Definitions—For definitions of terms used in this test method, refer to Terminology D1356. An explanation of units,
symbols, and conversion factors may be found in Practice IEEE/ASTM SI-10.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 absolute ultraviolet photometer—a photometer whose design, construction, and maintenance is such that it can measure the
absorbance caused by O mixtures without reference to external absorption standards. Given a value for the absorption coefficient
of O at 253.7 nm and a reading from the absolute ultraviolet photometer, O concentrations can be calculated with accuracy. An
3 3
absolute ultraviolet photometer is used only on prepared O mixtures free from interferences, as in calibration activity.
3.2.2 primary standard—a standard directly defined and established by some authority, against which all secondary standards are
compared.
3.2.3 secondary standard—a standard used as a means of comparison, but checked against a primary standard.
3.2.4 standard—an accepted reference sample or device used for establishing the measurement of a physical quantity.
3.2.5 transfer standard—a type of secondary standard; it is a transportable device or apparatus that, together with operational
procedures, is capable of reproducing pollutant concentrations or producing acceptable assays of pollutant concentrations.
4. Summary of Test Method
4.1 This test method is based on the absorption of ultraviolet radiation at 253.7-nm wavelength by O and the use of an
ozone-specific scrubber to generate a reference air stream with only O scrubbed from it. A single-cell ultraviolet absorption
photometer is used, with the cell filled alternately with ambient and O -scrubbed ambient air. The absorption to be measured at
the lower part of the operating range is extremely small. Special precautions and designs must be used to obtain accurate results.
4.2 The absorption of radiation at 253.7 nm by O at very low concentrations follows the Beer-Lambert Law. Namely, for a cell
of length d, assuming a constant input ultraviolet intensity, the ratio of the emerging intensities for the cell filled with sample air,
I , and with O -scrubbed air, I , is:
s 3 o
I
s
2~cad!
5 e (1)
I
o
where:
c = the concentration of O , ppm (v),
d = the length of the cell, cm, and
a = the absorption coefficient of O per length unit of d and per concentration unit of c.
4.3 When (cad) is << 1, as is the case for O at 253.7 nm in the concentration range specified for this test method, the
approximation
2x
e ' 12 x (2)
~ !
can be used to simplify the signal processing electronics, so that
I 'I ~12 cad! (3)
s o
and thus
I 2 I
~ !
o s
c' (4)
I ad
o
4.4 At 1 ppm (v), the high end of the recommended range, and a path length of 50 cm, the error resulting from application of the
above approximation is approximately 1 part in 10 000.
D5156 − 22
4.5 Thus, the concentration of O can be obtained from the difference between the signal from the photosensor (often a vacuum
photodiode) when the contents of the absorption cell contain sample air from which O has been scrubbed, and when it contains
sample air containing O .
−6
4.6 At 5 ppb (v) with a 50-cm path length, the absorption is approximately 308 × 0.005 × 50 × 10304.39 × 0.005 × 50 × 10
−5
or × 10 (1-45).
4.7 The instrument is calibrated by methods given in Practices D5011 and D5110, which describe the use of an absolute ultraviolet
photometer as a primary standard and the qualification and use of transfer standards.
5. Significance and Use
5.1 Standards for O in the atmosphere have been promulgated by government authorities to protect the health and welfare of the
public (56) and also for the protection of industrial workers (67).
5.2 Although O itself is a toxic material, in ambient air it is primarily the photochemical oxidants formed along with O in
3 3
polluted air exposed to sunlight that cause smog symptoms such as lachrymation and burning eyes. Ozone is much more easily
monitored than these photochemical oxidants and provides a good indication of their concentrations, and it is therefore the
substance that is specified in air quality standards and regulations.
6. Interferences
6.1 Any aerosol or gas that absorbs or scatters ultraviolet radiation at 253.7 nm, and that is removed by the O -specific scrubber,
constitutes an interferent (78) to this test method (89). Particulate matter can be removed with a poly-tetrafluoroethylene (PTFE)
membrane filter. Any type of filter can, however, become contaminated and may then scrub O . It is important to check the
O -inertness of such devices frequently.
6.2 Some reported positively interfering organic species for a manganese dioxide scrubber are tabulated in Annex A2 of this test
method. In general, if interferences are suspected, it is preferable to use another test method rather than to try to scrub out the
interfering agent, since the instability of O makes the testing and proving of additional interferant scrubbers particularly difficult.
6.3 Water vapor may constitute either a positive or negative interferant in instruments calibrated with dry span gas (9-10-1213).
6.3.1 Improperly polished absorption cell windows may lead to increased signal noise and apparent ozone increases in instruments
subject to rapidly changing humidity, such as at a coastal site where instruments may be exposed to frequent shifts between
relatively dry terrestrial and moist oceanic air parcels (89).
6.3.2 A negative water vapor interference, due to humidity dependent changes in elution rates of interferences from the ozone
scrubber may develop in manganese dioxide scrubbers exposed to ambient air (1011, 1213, 1314). This phenomenon is described
in 7.2.6.
7. Apparatus
7.1 Instruments are commercially available that meet the specifications provided in Annex A1. Note that these specifications do
not cover operation where the ambient temperature changes rapidly.
7.2 The elements of the typical ozone-measuring system are shown in Fig. 1. Assembled, they form a photometric ultraviolet
monitor with specifications conforming to those listed in Annex A1. The components are described in 7.2.1 – 7.2.8.
7.2.1 Ultraviolet Absorption Cell, constructed of materials inert to O , for example, PTFE-coated metal, borosilicate glass, and
fused silica. It shall be mechanically stable so that the optical alignments of the source, sensor, and any beam-directing devices
(mirror, prisms, or lenses) are not affected by changes in ambient temperature (Fig. 1(F)).
The boldface numbers in parentheses refer to the list of references at the end of this test method.
D5156 − 22
FIG. 1 Schematic Diagram of a Typical Ultraviolet Photometer
7.2.2 Ultraviolet Lamp—A low-pressure mercury vapor discharge lamp enclosed in a shield to prevent its radiation at 185 nm
185 nm (which generates O ) from reaching the absorption cell (Fig. 1(J)).
7.2.2.1 The lamp output at 253.7 nm shall be extremely stable, or provision shall be made to compensate for short-term variations
at 253.7-nm output, for example, by the use of a lamp-intensity monitor to measure output from the lamp and with electronics to
adjust the signal from the ultraviolet sensors correspondingly.
7.2.2.2 Shield, constructed of high-silica glass to remove the 185-nm line and permit the transmission at 253.7-nm radiation (Fig.
1(H)).
7.2.3 Particulate Filter, installed in the sample line to prevent aerosols or particulate matter from entering the measuring system.
PTFE fluorocarbon filters with pore sizes between 0.2 and 5.0 μm shall be used. The filter shall be replaced frequently since
accumulated materials on the filter may catalyze the breakdown of O into oxygen (Fig. 1(B)).
7.2.4 Sensor—Vacuum photodiodes with cesium telluride photocathode sensitivity at 253.7-nm radiation and negligible sensitivity
to the other mercury lamp lines. The response at 253.7 nm shall be extremely stable over the short-term periods of the sampling
cycle, of the same order as the stability demanded of the ultraviolet source. Temperature stabilization and a well-regulated
photosensor supply voltage shall be provided to achieve the necessary stability (Fig. 1(E)).
7.2.5 Three-Way PTFE Solenoid Valve, constructed with internal parts of, or coated with, PTFE fluorocarbon or other material that
will not catalyze the destruction of O , to route the sample through or to bypass the O selective scrubber (Fig. 1(C)).
3 3
7.2.6 Ozone-Specific Scrubber, containing a material that selectively catalyzes the destruction of O without altering or adding any
other compound. Manganese dioxide on a substrate and heated silver wool have been found generally to perform this function.
However, several aromatic organic compounds identified in Annex A2 have been shown to be adsorbed by manganese dioxide.
Some compounds may be adsorbed partly, producing at first an apparent higher concentration of O , followed by a falsely lower
concentration as the material is desorbed (1011). Mean O values are not affected by reversibly adsorbed species when averaging
times are much longer than that of the absorption-desorption cycle, provided that the possible “negative” O values that result from
the desorption of the interferant while actual O values are very low or zero are included in the mean. This may not be true where
hourly averages are calculated by simple arithmetical averaging of instantaneous values taken within a 1-h period, or where the
instrument contains a zero clamp that prevents negative values from being output (Fig. 1(D)). After exposure to ambient air, some
manganese dioxide ozone scrubbers may develop anomalous sensitivity to water vapor. Since such anomalous scrubbers regain
normality at low humidity, their anomalous behavior can not be detected during span gas calibrations using dry zero air. Scrubber
effıciency tests must be conducted with wet span gas to identify such anomalous manganese dioxide cartridges (1415, 1516).
7.2.7 Pump—A small air pump to pull the sample air through the instrument (Fig. 1(N)).
“Vycor” brand material has been found to be satisfactory.
D5156 − 22
7.2.8 Flowmeter, to verify that air is moving through the instrument (Fig. 1(L)).
7.3 Internal Lines and Fittings, in the sample stream prior to the adsorption cell and the scrubber, constructed of PTFE
fluorocarbon or other O -inert material.
7.4 Signal Processing Electronics, containing several distinct elements (Fig. 1(K)):
7.4.1 Circuits to condition the signal from the ultraviolet-sensitive sensor (diode) with short-term stability.
7.4.2 Timing and control circuits to operate the flow switching valves and different phases of the signal conditioning circuits.
7.4.3 Circuits to generate mean values from the signals from the sensor (diode) interface circuits for the two parts of the cycle,
to subtract them, and to output the resultant differences in a scaled form. The circuits shall also compensate for temperature and
pressure so that the adsorption measured is proportional to the gas density in the absorption cell.
7.4.4 The concentration of O can be obtained from the ratio of the sensor (diode) signals when the adsorption cell contains sample
air from which O has been scrubbed, to when it contains sample air containing O . The conversion of this value to parts per
3 3
million by volume shall include correction for ambient temperature and barometric pressure according to the ideal gas law. The
correction can be ignored if errors as great as 65 % are acceptable. Some commercially available instruments correct automatically
for actual measurement temperature and pressure in their concentration outputs.
7.4.5 Signal processing shall not prevent the output of negative values, which may arise from instrument malfunction, from
random fluctuations in measurements of I and I in the absence of O , and from interferences being desorbed from the O -selective
s o 3 3
scrubber.
7.5 Ports, included in the instrument at the entry and exit of the adsorption cell. These are helpful in determining whether O is
being destroyed in the cell. The calibration method given in Practice D5110 describes how the ports are used.
7.6 Barometer, to measure and record atmospheric pressure during sampling, in accordance with Test Methods D3631.
7.7 Temperature Measuring Equipment, to measure and record ambient temperature during sampling.
8. Hazards
8.1 See Practice D3249 for general safety precautions in using instruments.
8.2 The wavelength used for adsorption measurements is in the extreme ultraviolet, where eye damage is possible if the lamp is
viewed directly.
8.3 When calibrating the instrument, vent the excess gas mixture through a charcoal filter. This will prevent contamination of the
work area around the instrument with O , which, at the concentrations encountered at the high end of the method’s range, can
induce headaches and, occasionally, nausea.
9. Sampling
9.1 Sampling of the atmosphere shall be conducted in accordance with the guidelines given in Practices D1357 and D3249. These
recommended practices point out the need for avoiding sites that are closer than a 50-m distance from traffic, which could lead
to transient hydrocarbon and nitrogen oxide interferences.
9.2 The sampling lines shall
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