ASTM D8406-22

Standard Practice for Performance Evaluation of Ambient Outdoor Air Quality Sensors and Sensor-based Instruments for Portable and Fixed-point Measurement

SIGNIFICANCE AND USE
5.1 This practice establishes standardized tests for the performance evaluation of sensor-based continuous instruments for ambient air quality measurements. Public and private air monitoring interests have manifested themselves as a driving force for the deployment of air quality sensors and instruments to quantify air pollutant concentrations in communities, around schools, around industrial facilities, and elsewhere. Users of air quality sensors require information on the performance and limitations of these devices so that informed decisions regarding their suitability for various purposes can be determined. This practice describes both laboratory and field tests that provide information on candidate instrument repeatability, sensitivity, linearity, cross-interferences, drift and comparability with more costly instruments typically used by entities such as government agencies. The air quality sensors are first evaluated in a laboratory chamber by comparing their response to a reference instrument and challenging the gas sensors with interferents. The sensors are then deployed outdoors for field testing at two sites with different climates against reference air quality instruments. This practice is intended to be referenced in standards and codes that establish minimum performance quality for sensor-based ambient outdoor air monitoring.  
5.2 This practice is intended for air quality sensors that measure one or more of the criteria pollutants in ambient air (ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, PM10 and PM2.5) that can be operated in outdoor environments and can log a concentration reading. It is not intended for devices or transducers that require additional enclosures for deployment outdoors or post-processing to convert their output signal into a pollutant concentration reading.  
5.3 It is anticipated that the main users of this practice will be manufacturers, developers, and distributors of outdoor air quality sensors, air quality agenc...
SCOPE
1.1 This practice establishes standardized tests for the performance evaluation of sensor-based continuous instruments for ambient outdoor air quality measurements. It describes both laboratory and field tests that provide information on candidate sensor repeatability, sensitivity, linearity, cross-interferences, drift, and comparability against reference instruments.  
1.2 This practice does not apply to sensors or instruments that remotely measure atmospheric pollutants using open path, lidar, or imaging technology.  
1.3 The evaluation procedures contained in this practice are for sensors that alone or in combination measure outdoor criteria pollutants in ambient air: particulate matter (PM2.5 and PM10), sulfur dioxide (SO2), ozone (O3), carbon monoxide (CO), or nitrogen dioxide (NO2) at concentrations that are relevant to public health.  
1.4 Testing is to be performed by a competent entity able to demonstrate that it operates in conformity with internationally accepted test laboratory quality standards such as ISO/IEC 17025.  
1.5 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 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.  
1.7 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: 13.040.20 - Ambient atmospheres
• Technical Committee: D22 - Air Quality
• Drafting Committee: D22.03 - Ambient Atmospheres and Source Emissions

Relations

• Refers: ASTM E3080-23 - Standard Practice for Regression Analysis with a Single Predictor Variable
• Effective Date: 01-Nov-2023
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• 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 E3080-19 - Standard Practice for Regression Analysis with a Single Predictor Variable
• Effective Date: 01-Sep-2019
• Refers: ASTM E3080-17 - Standard Practice for Regression Analysis
• Effective Date: 01-Nov-2017
• Refers: ASTM E456-13A(2017)e3 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM E456-13A(2017)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM D5011-17 - Standard Practices for Calibration of Ozone Monitors Using Transfer Standards
• Effective Date: 01-Oct-2017
• Refers: ASTM E3080-16 - Standard Practice for Regression Analysis
• Effective Date: 01-Nov-2016
• Refers: ASTM E178-16 - Standard Practice for Dealing With Outlying Observations
• Effective Date: 01-Jun-2016
• 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

Overview

ASTM D8406-22: Standard Practice for Performance Evaluation of Ambient Outdoor Air Quality Sensors and Sensor-based Instruments for Portable and Fixed-point Measurement provides a comprehensive framework for evaluating the performance of air quality sensors. Developed by ASTM International, this standard practice is essential for ensuring that sensor-based instruments used in ambient outdoor air monitoring produce reliable, accurate, and comparable data. The practice is especially significant given the growing deployment of air quality sensors in communities, near schools, and around industrial sites by public agencies, manufacturers, and environmental organizations.

Key Topics

• Standardized Performance Evaluation: The practice defines both laboratory and field tests to assess key performance metrics such as repeatability, sensitivity, linearity, cross-interference, drift, and comparability to reference-grade instruments.
• Criteria Pollutants Addressed: Focuses on sensors measuring outdoor criteria pollutants, specifically particulate matter (PM2.5 and PM10), sulfur dioxide (SO₂), ozone (O₃), carbon monoxide (CO), and nitrogen dioxide (NO₂).
• Laboratory Evaluation: Sensors are first subjected to controlled laboratory conditions, including exposure to various concentrations of pollutants and interferents, compared against calibrated reference instruments.
• Field Testing: Following lab assessments, sensors are deployed for real-world testing at two different climate sites, ensuring performance validation across diverse environmental conditions.
• Quality Assurance: Requires that all testing be conducted by facilities conforming to internationally recognized laboratory quality standards, such as ISO/IEC 17025.

Applications

ASTM D8406-22 is highly valuable for a variety of stakeholders involved in air quality assessment and management:

• Manufacturers and Developers: Provides a clear, standardized methodology for evaluating new and existing sensor-based instruments, facilitating product development and quality assurance.
• Regulatory Agencies and Air Quality Authorities: Assists in verifying that deployed air monitoring sensors meet minimum standards for public health-related decision making and regulatory compliance.
• Environmental Consultants: Enables informed recommendations regarding the suitability and limitations of different air quality sensors for client projects.
• Community and Educational Organizations: Offers guidance for trustworthy deployment of portable or fixed-point air quality sensors for monitoring local environments, promoting public awareness and data accuracy.
• Standard Setting Bodies: Serves as a reference in developing codes and regulations that specify the minimum performance criteria for ambient air sensor systems.

Related Standards

ASTM D8406-22 references and complements several other standards and guidelines central to air quality measurement and sensor evaluation:

• ASTM D1356: Terminology Relating to Sampling and Analysis of Atmospheres
• ASTM D1914: Conversion Units and Factors Relating to Sampling and Analysis of Atmospheres
• ASTM D3162, D3249, D3824: Test and calibration methods for ambient air analyzers
• ASTM D5011, D5110: Calibration of ozone monitors
• ASTM D8405: Evaluation of PM2.5 sensors for indoor air
• ISO/IEC 17025: General requirements for the competence of testing and calibration laboratories
• US 40 CFR Part 58: Ambient Air Quality Surveillance
• EN 14626, EN 14625: European standards for measurement methods of specific air pollutants

Practical Value

Implementing ASTM D8406-22 ensures rigorous, repeatable, and transparent performance evaluation of air quality sensors, supporting the integrity of ambient air monitoring. This standard empowers users to make informed decisions about instrument deployment, guarantees data quality for regulatory and public health uses, and promotes global consistency in air pollutant monitoring technologies.

Keywords: air quality sensors, outdoor air monitoring, sensor evaluation, ASTM D8406-22, criteria pollutants, performance testing, ambient air, PM2.5, PM10, SO₂, O₃, CO, NO₂, laboratory evaluation, field testing, air pollution 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: D8406 − 22
Standard Practice for
Performance Evaluation of Ambient Outdoor Air Quality
Sensors and Sensor-based Instruments for Portable and
Fixed-point Measurement
This standard is issued under the fixed designation D8406; 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 2. Referenced Documents
1.1 This practice establishes standardized tests for the per- 2.1 ASTM Standards:
formance evaluation of sensor-based continuous instruments D1356Terminology Relating to Sampling and Analysis of
forambientoutdoorairqualitymeasurements.Itdescribesboth Atmospheres
laboratoryandfieldteststhatprovideinformationoncandidate D1914PracticeforConversionUnitsandFactorsRelatingto
sensor repeatability, sensitivity, linearity, cross-interferences, Sampling and Analysis of Atmospheres
drift, and comparability against reference instruments. D3162Test Method for Carbon Monoxide in the Atmo-
sphere(ContinuousMeasurementbyNondispersiveInfra-
1.2 This practice does not apply to sensors or instruments
red Spectrometry)
that remotely measure atmospheric pollutants using open path,
D3249Practice for General Ambient Air Analyzer Proce-
lidar, or imaging technology.
dures
1.3 The evaluation procedures contained in this practice are
D3824Test Methods for Continuous Measurement of Ox-
for sensors that alone or in combination measure outdoor
idesofNitrogenintheAmbientorWorkplaceAtmosphere
criteria pollutants in ambient air: particulate matter (PM and
2.5
by Chemiluminescence
PM ), sulfur dioxide (SO ), ozone (O ), carbon monoxide
10 2 3
D5011Practices for Calibration of Ozone Monitors Using
(CO), or nitrogen dioxide (NO ) at concentrations that are
Transfer Standards
relevant to public health.
D5110Practice for Calibration of Ozone Monitors and
CertificationofOzoneTransferStandardsUsingUltravio-
1.4 Testing is to be performed by a competent entity able to
demonstrate that it operates in conformity with internationally let Photometry
accepted test laboratory quality standards such as ISO/IEC D6332Guide for Testing Systems for Measuring Dynamic
Responses of Carbon Monoxide Detectors to Gases and
17025.
Vapors
1.5 Units—The values stated in SI units are to be regarded
D8405Test Method for Evaluating PM Sensors or Sensor
2.5
asstandard.Nootherunitsofmeasurementareincludedinthis
Systems Used in Indoor Air Applications
standard.
E178Practice for Dealing With Outlying Observations
1.6 This standard does not purport to address all of the
E456Terminology Relating to Quality and Statistics
safety concerns, if any, associated with its use. It is the
E3080Practice for Regression Analysis with a Single Pre-
responsibility of the user of this standard to establish appro-
dictor Variable
priate safety, health, and environmental practices and deter-
2.2 Other References:
mine the applicability of regulatory limitations prior to use.
29 CFR 1910.101 Compressed gases (general require-
1.7 This international standard was developed in accor-
ments)
dance with internationally recognized principles on standard-
40 CFR Part 58Ambient Air Quality Surveillance
ization established in the Decision on Principles for the
EN 14626:2012Ambient air – Standard method for the
Development of International Standards, Guides and Recom-
measurement of the concentration of carbon monoxide by
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
ThispracticeisunderthejurisdictionofASTMCommitteeD22onAirQuality contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
and is the direct responsibility of Subcommittee D22.03 on Ambient Atmospheres Standards volume information, refer to the standard’s Document Summary page on
and Source Emissions. the ASTM website.
Current edition approved Sept. 1, 2022. Published October 2022. DOI: 10.1520/ Available from U.S. Government Publishing Office (GPO), 732 N. Capitol St.,
D8406-22. NW, Washington, DC 20401, http://www.gpo.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8406 − 22
non-dispersive infrared spectroscopy toquantifyairpollutantconcentrationsincommunities,around
EN 14625:2012Ambient air – Standard method for the schools,aroundindustrialfacilities,andelsewhere.Usersofair
measurement of the concentration of ozone by ultraviolet quality sensors require information on the performance and
photometry limitations of these devices so that informed decisions regard-
Directive2008/50/ECoftheEuropeanParliamentandofthe ing their suitability for various purposes can be determined.
Council of 21 May 2008 on ambient air quality and This practice describes both laboratory and field tests that
cleaner air for Europe provide information on candidate instrument repeatability,
ISO/IEC 17025:2017General requirements for the compe- sensitivity, linearity, cross-interferences, drift and comparabil-
tence of testing and calibration laboratories itywithmorecostlyinstrumentstypicallyusedbyentitiessuch
ISO 6145-7:2018Gas analysis – Preparation of calibration as government agencies. The air quality sensors are first
gas mixtures using dynamic methods Part 7: Thermal evaluatedinalaboratorychamberbycomparingtheirresponse
mass-flow controllers to a reference instrument and challenging the gas sensors with
interferents. The sensors are then deployed outdoors for field
3. Terminology
testing at two sites with different climates against reference air
quality instruments. This practice is intended to be referenced
3.1 Definitions:
in standards and codes that establish minimum performance
3.1.1 Fordefinitionsoftermsusedinthispracticeotherthan
quality for sensor-based ambient outdoor air monitoring.
those following, refer to Terminologies D1356 and E456.
3.1.2 air quality sensor, n—a physical device that uses one
5.2 This practice is intended for air quality sensors that
ormoresensorstomeasureandreporttheconcentrationofone
measure one or more of the criteria pollutants in ambient air
or more analytes (pollutants) in outdoor air.
(ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide,
PM andPM )thatcanbeoperatedinoutdoorenvironments
3.1.3 analyte, n—the substance (air pollutant) measured by
10 2.5
and can log a concentration reading. It is not intended for
the air quality sensor or analyzer.
devices or transducers that require additional enclosures for
3.1.4 full scale, n—the designated maximum concentration
deploymentoutdoorsorpost-processingtoconverttheiroutput
for performance testing determined by either the measurement
signal into a pollutant concentration reading.
range of the sensor or the reference analyzer (whichever is
lower). 5.3 It is anticipated that the main users of this practice will
be manufacturers, developers, and distributors of outdoor air
3.1.5 instrument, n—see air quality sensor.
quality sensors, air quality agencies, and environmental con-
3.1.6 interferent, n—asubstanceotherthanthecompoundof
sultants.
interest that causes a bias in the sensor output.
3.1.7 reading, n—the analytical result obtained from a
6. Apparatus
digital display or indicated on a scale or dial affixed to or
6.1 Gas dilution and delivery system for the continuous
recording output from a sensor or instrument.
generation of test mixtures from gas standards and zero-air
operated according to ISO 6145-7.
4. Summary of Practice
6.2 Ozone analyzerthatisontheUSEPAListofDesignated
4.1 This is a practice for evaluating ambient air quality
Reference and Equivalent Methods for ozone or conforms to
sensor performance. This document contains definitions and
EN14625 or is on the MCERTS list of Certified Products:
terms, sampling information, calibration techniques, methods
Continuous Ambient Air Monitoring System or has been
forvalidatingresults,andgeneralcommentsrelatedtoambient
approved by a national standards body for ambient monitoring
air sensors and sensor-based instruments. This practice is
and has been calibrated according to Practices D5011.
applicabletosensorsandsensor-basedinstrumentsthatsample
ambient air through diffusion or passive sampling as well as 6.3 Sulfur dioxide analyzer that is on the USEPA List of
through active sampling using a pump or fan. This practice
Designated Reference and Equivalent Methods for sulfur
compriseslaboratoryandfieldteststoevaluateperformanceof dioxide or conforms to EN14212 or is on the MCERTS list of
gas sensors and particulate matter sensors. Certified Products: Continuous Ambient Air Monitoring Sys-
tem or has been approved by a national standards body for
5. Significance and Use
ambient monitoring.
5.1 This practice establishes standardized tests for the per-
6.4 Nitrogen dioxide analyzer that is on the USEPAList of
formance evaluation of sensor-based continuous instruments
Designated Reference and Equivalent Methods for nitrogen
for ambient air quality measurements. Public and private air
dioxide or conforms to EN14211 or is on the MCERTS list of
monitoring interests have manifested themselves as a driving
Certified Products: Continuous Ambient Air Monitoring Sys-
force for the deployment of air quality sensors and instruments
tem orconformstoTestMethodsD3824orhasbeenapproved
by a national standards body for ambient monitoring.
Available from European Committee for Standardization (CEN), Avenue
Marnix 17, B-1000, Brussels, Belgium, http://www.cen.eu.
5 6
Available from International Organization for Standardization (ISO), ISO https://www.csagroupuk.org/services/mcerts/mcerts-product-certification/
Central Secretariat, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva, mcerts-certified-products/mcerts-certified-products-continuous-ambient-air-
Switzerland, https://www.iso.org. monitoring-system/ (Accessed 26 May 2021).
D8406 − 22
6.5 Carbon monoxide analyzerthat is on the USEPAList of 7.2 Test Gas Mixtures (not ozone)—These contain concen-
Designated Reference and Equivalent Methods for carbon trations of the test gas in nitrogen or air. The gas mixtures are
monoxide or conforms to EN14626 or is on the MCERTS list certified with 62% uncertainty of the stated value and are to
of Certified Products: Continuous Ambient Air Monitoring be supplied in high- pressure cylinders.
System or conforms to Test Method D3162 or has been
7.3 Zero-air—Airthatissubstantivelyfreeofcontaminants.
approvedbyanationalstandardsbodyforambientmonitoring.
The specification of the purity of the zero-air is given in Table
6.6 Continuous PM instrument that is on the current 1. Zero-air is supplied at a temperature of 20°C 6 2 °C and
2.5
USEPAList of Designated Reference and Equivalent Methods relative humidity of 30% 6 5 %. Zero-air is used to dilute all
for PM or conforms to EN16450 or is on the MCERTS list calibration gases to produce the required test gas concentra-
2.5
of Certified Products: Continuous Ambient Air Monitoring tions.
System orhasbeenapprovedbyanationalstandardsbodyfor
7.4 Particle-free Air—Dry air which has been filtered to
ambient monitoring. 3
contain PM at a level of less than 1 µg/m .
6.7 Continuous PM instrument that is on the current
8. Hazards
USEPAList of Designated Reference and Equivalent Methods
forPM orconformstoEN16450orisontheMCERTSlistof
8.1 Eachsensorandmanualisreviewedtoensurethesensor
Certified Products: Continuous Ambient Air Monitoring Sys-
conforms to applicable electrical, optical, radio, and power
tem or has been approved by a national standards body for
safety requirements such as CE, FCC, IEC. If conformity is
ambient monitoring.
unclear, testing shall stop and the manufacturer contacted to
provide documentation on safety in usage of the sensor and its
6.8 Aerosol generation system able to produce monodis-
components. Testing can resume once the test laboratory is
perse polystyrene latex spheres in the range 0.5µm to 1.5µm
satisfied that the sensor is safe to test.
for the evaluation of PM sensors and in the range 4.0µm to
2.5
8.0µm for the evaluation of the PM sensors.
10 8.2 Compressed gas standards shall be handled in accor-
dance with 29 CFR 1910.101, in well-ventilated locations
6.9 Exposure chamberabletoenclosetheairqualitysensors
away from sparks and flames. Improper handling of com-
undertestandexposethemtotestconcentrationsofpollutants.
pressed gas cylinders can result in explosion. Cylinders and
The chamber for testing gas sensors is constructed following
permeation devices containing high purity CO and NO are
thedesignprinciplesdescribedinGuideD6332andbemadeof
flammable and harmful if inhaled. Cylinders containing mix-
inert materials that will not react with the test gases. The
tures of CO, SO , NO, and NO in air or nitrogen may be
chamber for PM and PM sensor testing is constructed
2 2
2.5 10
harmfulifinhaled.Rapidreleaseofgasmixtureswithnitrogen
following the design principles described in Test Method
as the balance gas can result in asphyxiation. Compressed air
D8405. The chamber has a means of bringing in outside
supports combustion.
ambient air to expose sensors to ambient conditions during
8.2.1 Gascylindersmustbefastenedtoarigidstructureand
periods between tests. A description of a suitable chamber
not exposed to direct sunlight or heat as per 29 CFR 1910.101.
designthatmeetsthedesignprinciplesforbothgasandaerosol
8.2.2 Special safety precautions shall be taken when using
testing is given in the literature.
or storing combustible or toxic gases to ensure that the system
6.10 Zero-air source for generating zero- air as described in
is safe and free from leaks. Review the Safety Data Sheets
Guide D6332 and which can generate zero-air with the
(SDS) for all materials and be sure to use proper safety
specification defined in 7.3.
precautions.
6.11 Humidification module for humidifying the zero-air
and test gas as described in Guide D6332. 9. Procedure
6.12 Temperature measurement apparatus able to measure 9.1 Two identical air quality sensor units or instruments are
from –10 °C to 50 °C with a maximum error of 0.5 °C needed for evaluation.All units are evaluated concurrently and
calibratedagainstreferencetemperaturestandardsaccordingto theresultsforeachunitarereported.Ifafaultorfailureoccurs
the manufacturer’s instructions for recording test conditions. with one or more of the units, the testing of the faulty units is
stopped, the fault fixed or the units replaced, the previous test
6.13 Humidity measurement apparatus able to measure
results invalidated, and all laboratory and field tests repeated.
relative humidity from 10% to 90 % RH with a maximum
error of 3 % calibrated against reference humidity standards 9.2 Each test is performed for each analyte the sensor units
according to the manufacturer’s instructions for recording test measure. The laboratory tests are completed before the field
conditions.
7. Reagents and Materials TABLE 1 Maximum Zero-air Pollutant Levels
Pollutant Concentration
7.1 Ozone sourceforgenerationoftestmixturesofO inair
Ozone, Nitrogen dioxide, Sulfur dioxide, Each pollutant# 1 nmol/mol
as described in Practices D5110 and D5011.
Hydrogen sulfide, Ammonia
Papapostolou, Vasileios & Zhang, Hang & J. Feenstra, Brandon & Polidori,
Carbon monoxide # 0.05 µmol/mol
Andrea, “Development of an environmental chamber for evaluating the perfor-
mance of low-cost air quality sensors under controlled conditions,” Atmospheric Total hydrocarbons # 0.5 µmol/mol
Environment, Vol 171, 2017, pp 82–90.
D8406 − 22
test. If the sensor has a pump-based sampling system which 9.4.2.1 Provide zero-air to the instrument as confirmed by
can be connected to a sampling line, the analyte test mixtures thereferenceanalyzer,waitfor30minandthenrecordthenext
canbegeneratedinthesamplinglineandsuppliedtothesensor 20 independent results (X ). The repeatability at zero is
z,i
provided the sample pressure is the same as ambient pressure. defined as the standard deviation (S ) calculated according to:
If the sensor uses diffusion or fan-based sampling or if the
n
manufacturer requests it, then the sensor is exposed to analyte ¯
~X 2 X!
( z,i
i51
test mixtures inside the exposure chamber (6.9).
S 5 (3)
!
n 2 1
9.3 All test concentrations are measured using the reference
where:
analyzers described in Section 6.All reference analyzers shall
S = standard deviation at zero,
becalibratedwithinoneweekofthestartofthelaboratorytests
n = number of measurements,
according to the manufacturer’s instruction. All reference
X = consecutive individual sensor results at zero, and
z,i
analyzers shall be zero and span adjusted at 70% to 80 % of
¯
X = mean of individual sensor results at zero.
full scale (see 3.1.4) each day prior to the start of laboratory
tests. The sensors shall also be zero and span adjusted at 70%
9.4.3 Repeatability at Span:
to 80 % of full scale each day, using the same reference 9.4.3.1 Supply the sensor under test with the test analyte at
standard, prior to the start of laboratory testing. If the sensors
the concentration given in Table 2 as confirmed by the
arenotabletobezeroandspanadjusted,theyshouldbetested referenceanalyzer,waitfor30minandthenrecordthenext20
without adjustment. Temperature and humidity of the test
independent results (X )
s,i
mixturesgeneratedshallbe20°C 61°Cand30% 62%RH 9.4.3.2 The repeatability at span is defined as the standard
respectively, unless otherwise stated.
deviation (S ) calculated according to:
s
n
9.4 Laboratory Evaluation of O ,NO ,SO , CO, Sensors
3 2 2 2
¯
~X 2 X!
s,i
and Sensor-based Instruments—Ensure the test sensors are (
i51
S 5 (4)
!
warmed up and operating according to the manufacturer s
n 2 1
instructions and are calibrated. All laboratory test readings
where:
must be recorded at one minute intervals or the minimum
S = standard deviation at span,
reporting frequency of the sensor if this is greater than one
s
n = number of measurements,
minute.
X = consecutive individual sensor results at span, and
s,i
9.4.1 Lack of Fit:
¯
X = mean of individual sensor results at span.
9.4.1.1 Supply the sensor with analyte concentrations at
9.4.4 Limit of Detection:
0%, 95 %, 25 %, 75 %, and 50 % of full scale in that order.
9.4.4.1 The limit of detection (LOD) for the sensor mea-
Once the correct concentration is reached by the gas delivery
surement of the analyte is given by:
systemaccordingtothereferenceanalyzer,waitfor30minand
then record the mean of the next 10 readings of the sensor and
LOD=3S (5)
analyzer. Calculate the linear regression through the mean
9.4.5 Short-term Drift:
responses at each concentration according to Practice E3080.
9.4.5.1 Supply zero-air and wait 30 min then record 20
Theresidualsateachconcentrationarecalculatedaccordingto:
independentreadingsandcalculatethemean(C ).Supplythe
z,1
r 5 Y 2 A 1 Bc (1)
~ !
c a,c
analyte gas at the stated test concentration in Table 2, for 30
min then record 20 independent readings and calculate the
where:
mean (C ). Keep the sensor running for 24 h sampling
s,1
r = residual at concentration c,
c
outdoor ambient air. After 24 h, supply zero-air and wait 30
Y = mean of the 10 sensor readings at each concentration
a,c
min then record 20 independent readings and calculate the
c,
mean (C ). Supply analyte gas at the same concentration as
z,2
A = intercept of the linear regression line,
supplied at the start of the test for 30 min then record 20
B = slope of
...