ASTM D8405-21

Standard Test Method for Evaluating PM<inf>2.5</inf> Sensors or Sensor Systems Used in Indoor Air Applications

SIGNIFICANCE AND USE
5.1 Poor indoor air quality has been implicated in significant adverse acute and chronic impacts on occupant health and performance. The ability to assess the components contributing to poor indoor air quality is critical for determining best practices for improving indoor air quality.  
5.2 Measurement of pollutants in indoor environments using sensors and sensor systems provides information needed to improve indoor air quality through pollutant source control, ventilation, filtration or other treatments.  
5.3 This method uses a test characterization chamber system equipped with reference monitor(s) to evaluate the response of test sensors or test sensor systems to specific types of particles (for example, salt, polystyrene latex, or dust). To facilitate reproducible results, the test particles used within this method are standardized and have known properties. The user is cautioned that a single particle type is not representative of all particles found indoors. The relative response of test sensors or test sensor systems to a reference monitor can vary by a factor of two for different particle types (for example, primary or secondary, organic or inorganic, outdoor or indoor origin; see 6.11.3 for further discussion). Furthermore, the user is cautioned that the lower limit of particle size detection for optical test sensors and test sensor systems is generally 0.3 μm in diameter; particles below this size are generally undetected and may represent a significant health concern as well.
SCOPE
1.1 This test method uses a chamber system to evaluate the performance of stationary PM2.5 sensors (sensors) and particle sensor systems (sensor systems) subjected to various test conditions, including temperature, relative humidity, PM2.5 concentration, and coarse PM interferent concentration.  
1.1.1 This test method covers sensors and sensor systems that can be continuously powered and continuously operated for the duration of any test described in this method through line power or an internal battery of sufficient output. This test method is not meant to evaluate sensors or sensor systems without these capabilities.  
1.1.2 This test method evaluates the performance of sensors and sensor systems that allow users to collect data in a systemic manner to assess the capabilities and limitations of these devices.  
1.1.3 This test method is not meant to evaluate sensors or sensor systems without data storage and recording capabilities.  
1.1.4 This test method is not intended to evaluate indoor air quality sensors and sensor systems for purposes of regulation of outdoor air, homeland security, law enforcement or forensic activity.  
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
1.3 The text of this standard references notes and footnotes that provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard.  
1.4 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.  
1.5 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-2021
• ICS: 13.040.30 - Workplace atmospheres
• Technical Committee: D22 - Air Quality
• Drafting Committee: D22.05 - Indoor Air

Relations

• Refers: ASTM E3080-23 - Standard Practice for Regression Analysis with a Single Predictor Variable
• Effective Date: 01-Nov-2023
• 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 D6330-20 - Standard Practice for Determination of Volatile Organic Compounds (Excluding Formaldehyde) Emissions from Wood-Based Panels Using Small Environmental Chambers Under Defined Test Conditions
• Effective Date: 01-Mar-2020
• 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 E3080-16 - Standard Practice for Regression Analysis
• Effective Date: 01-Nov-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
• Refers: ASTM D6330-98(2014) - Standard Practice for Determination of Volatile Organic Compounds &#40;Excluding Formaldehyde&#41; Emissions from Wood-Based Panels Using Small Environmental Chambers Under Defined Test Conditions
• Effective Date: 01-Nov-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 E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011

Overview

ASTM D8405-21 is the Standard Test Method for Evaluating PM_2.5 Sensors or Sensor Systems Used in Indoor Air Applications, developed by ASTM International. This standard provides a comprehensive framework for assessing the performance of stationary particulate matter (PM_2.5) sensors and sensor systems in controlled indoor environments. The method outlines the use of characterization chambers, reference monitors, and standardized test conditions to produce reliable, reproducible results essential for evaluating sensor accuracy, precision, and other critical operational characteristics.

Indoor air quality is a growing concern due to its impact on occupant health and productivity. Reliable PM_2.5 measurements enable informed decisions on ventilation, filtration, and pollutant control strategies within buildings. ASTM D8405-21 equips manufacturers, researchers, and building professionals with a consistent approach for comparing sensor technologies before market deployment or large-scale indoor air monitoring projects.

Key Topics

• Significance of Indoor PM_2.5 Monitoring

  • Ensures occupant health and performance through improved indoor air quality monitoring.
  • Recognizes the acute and chronic health issues linked to fine particulate matter exposure.

• Standardized Evaluation Method

  • Utilizes a chamber-based system with reference monitors to assess sensor response under controlled variables such as temperature, relative humidity, PM_2.5 concentration, and potential interferents.
  • Applies standardized, well-characterized test particles for reproducibility.

• Sensor System Requirements

  • Applicable to sensors and sensor systems capable of continuous operation with onboard data storage and retrieval capabilities.
  • Excludes portable or non-continuously powered devices.

• Performance Metrics

  • Evaluates parameters including average, standard deviation, relative standard deviation, bias, precision, mean error, recovery, susceptibility to environmental factors, and response to particles of varying types and origins.
  • Considers the detection limitations of sensor technology, particularly for particles below 0.3 μm diameter.

Applications

• Sensor Development and Quality Assurance

  • Enables manufacturers to benchmark PM_2.5 sensor and sensor system performance, supporting research and development of more accurate air quality monitoring equipment.

• Building Environmental Monitoring

  • Assists building professionals in selecting PM_2.5 sensors that are reliable under anticipated indoor air conditions, supporting occupancy health, safety, and comfort goals.

• Academic and Regulatory Research

  • Provides a foundation for research studies assessing indoor pollutant measurement technologies, helping to shape indoor air quality management policies and best practices.

• Facility Management

  • Supports facility managers and environmental consultants in verifying the efficacy of installed air monitoring solutions and in decision-making regarding ventilation, filtration, or pollutant source control approaches.

Related Standards

Several referenced documents and standards complement ASTM D8405-21, enhancing sensor evaluation and data interpretation:

• ASTM D1356: Terminology Relating to Sampling and Analysis of Atmospheres.
• ISO 8573-1: Requirements for purity of compressed air in terms of particles, water, and oil.
• ISO 17025: General requirements for the competence of testing and calibration laboratories.
• US EPA Title 40 Parts 53 & 58: Requirements for ambient particulate instruments and particulate matter fraction terminology.
• ASTM D6330: Practice for VOC emissions determination using environmental chambers.
• ASTM E691: Practice for conducting interlaboratory studies to determine precision of test methods.

ASTM D8405-21 aligns with internationally recognized principles established by the WTO Technical Barriers to Trade Committee, ensuring global relevance.

---

Keywords: ASTM D8405-21, PM2.5 sensor evaluation, indoor air quality, particulate matter measurement, reference monitor, sensor system testing, standardized test method, environmental chamber, indoor pollution monitoring, air quality standards, particle sensor performance.

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: D8405 − 21
Standard Test Method for
Evaluating PM Sensors or Sensor Systems Used in
2.5
Indoor Air Applications
This standard is issued under the fixed designation D8405; 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 ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.1 This test method uses a chamber system to evaluate the
mendations issued by the World Trade Organization Technical
performance of stationary PM sensors (sensors) and particle
2.5
Barriers to Trade (TBT) Committee.
sensor systems (sensor systems) subjected to various test
conditions, including temperature, relative humidity, PM
2.5
2. Referenced Documents
concentration, and coarse PM interferent concentration.
2.1 ASTM Standards:
1.1.1 This test method covers sensors and sensor systems
D1356 Terminology Relating to Sampling and Analysis of
that can be continuously powered and continuously operated
Atmospheres
for the duration of any test described in this method through
D3670 Guide for Determination of Precision and Bias of
line power or an internal battery of sufficient output. This test
Methods of Committee D22
method is not meant to evaluate sensors or sensor systems
D6330 Practice for Determination of Volatile Organic Com-
without these capabilities.
pounds(ExcludingFormaldehyde)EmissionsfromWood-
1.1.2 This test method evaluates the performance of sensors
Based Panels Using Small Environmental Chambers Un-
andsensorsystemsthatallowuserstocollectdatainasystemic
der Defined Test Conditions
manner to assess the capabilities and limitations of these
E691 Practice for Conducting an Interlaboratory Study to
devices.
Determine the Precision of a Test Method
1.1.3 This test method is not meant to evaluate sensors or
E3080 Practice for Regression Analysis with a Single Pre-
sensor systems without data storage and recording capabilities.
dictor Variable
1.1.4 This test method is not intended to evaluate indoor air
quality sensors and sensor systems for purposes of regulation
2.2 International Standards Organization (ISO) Standards:
of outdoor air, homeland security, law enforcement or forensic
ISO 8573-1 Requirements for the purity of compressed air
activity.
with respect to particles, water, and oil
ISO 12103-1 Road vehicles — Test contaminants for filter
1.2 The values stated in SI units are to be regarded as
evaluation — Part 1: Arizona test dust
standard. The values given in parentheses after SI units are
ISO 17025 General requirements for the competence of
provided for information only and are not considered standard.
testing and calibration laboratories
1.3 The text of this standard references notes and footnotes
2.3 United States (U.S.) Code of Federal Regulations
that provide explanatory material. These notes and footnotes
(CFR):
(excluding those in tables and figures) shall not be considered
Title 40 Part 53 Requirements for ambient particulate instru-
as requirements of the standard.
ments to attain U.S. Environmental Protection Agency
1.4 This standard does not purport to address all of the
(EPA) Federal Equivalent Method (FEM) designations
safety concerns, if any, associated with its use. It is the
Title 40 Part 58 Terminology relating to particulate matter
responsibility of the user of this standard to establish appro-
fractions
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accor-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
dance with internationally recognized principles on standard-
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 International Organization for Standardization (ISO), ISO
This test method is under the jurisdiction of ASTM Committee D22 on Air Central Secretariat, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
Quality and is the direct responsibility of Subcommittee D22.05 on Indoor Air. Switzerland, https://www.iso.org.
Current edition approved Sept. 1, 2021. Published October 2021. DOI: 10.1520/ Available from U.S. Government Publishing Office (GPO), 732 N. Capitol St.,
D8405-21. 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
D8405 − 21
2.4 U.S. EPA Standards: 3.2.8 PM sensor, n—a device capable of reporting the
2.5
Method IP-10A Determination of respirable particulate mat- concentration of PM in the air without additional manipula-
2.5
ter in indoor air tion of the data.
2.5 U.S. Department of Energy (DOE) Standards:
3.2.9 PM,n—particles with an aerodynamic diameter less
c
DOE-STD-3020 SpecificationforHEPAfiltersusedbyDOE
than or equal to 10 µm and greater than 2.5 µm, often referred
contractors
to as “coarse” PM; equivalent to the difference between PM
and PM ; equivalent to the definition of PM as defined
2.5 10–2.5
3. Terminology
in the U.S. CFR Title 40, Part 58.
3.1 Definitions—For definitions of terms used in this test
3.2.10 reference monitor, n—an instrument with a U.S. EPA
method, refer to Terminology D1356.
performance designation of Class III FEM for PM , exclud-
2.5
3.2 Definitions of Terms Specific to This Standard:
ing those using beta attenuation techniques, measuring particle
3.2.1 indoor air, n—air within an enclosed space (structure
mass concentration or particle mass size distribution, or both,
or vehicle), which is (1) intended for habitation, employment,
against which test sensors or test sensor systems are compared.
leisure, retail, transport, or any other forms of occupation by
3.2.10.1 Discussion—The U.S. EPA FEM designation (1)
humans and (2) conditioned for temperature or relative humid-
is only applicable to, and valid for, stationary ambient moni-
ity (RH), or both, or does not allow for free air change with
toring applications. However, FEM designation is required for
outdoor air other than through unintentional leakage or filtered
reference monitors used within this test method to provide a
mechanical ventilation.
reasonable level of confidence in the acceptability of the
reference monitor’s accuracy and precision.
3.2.2 indoor air quality particle sensors, n—sensors used to
measure and report particle content of indoor air and intended
3.2.11 sensor system, n—a collection of sensors with inte-
for use in indoor air quality applications.
grated power, integrated communication to a user interface,
and a user interface.
3.2.3 intra-model, adj—within a group of sensor systems of
the same make, model, and firmware version. Intra-model
3.2.12 test characterization chamber, n—a chamber into
results are developed by applying a mathematical operation to
which test sensors or test sensor systems are placed, into which
a data set developed from testing multiple test sensors or test
particles are introduced to evaluate the performance of the test
sensor systems of the same make, model, and firmware
sensor or test sensor system, and from which the reference
version.
monitor(s) is (are) sampling.
3.2.4 intra-unit, adj—within an individual unit. Intra-unit
3.2.13 test sensor, n—a single sensor evaluated according to
results are developed by applying a mathematical operation to
this test method.
a data set developed from testing one test sensor or test sensor
3.2.14 test sensor system, n—a sensor system evaluated
system.
according to this test method.
3.2.5 particle-negligible air, n—purified air for which
3.2.15 test system, n—a system including a test character-
particles, moisture and other substances that can interfere with
ization chamber, reference monitor(s), particle systems, and
a measurement are reduced to meet or exceed purity as
other equipment needed to generate the conditions required for
specified in ISO 8573-1 for Class 2.4.1 air, that is: solid
this test method.
particulate number concentrations not exceeding (1) 400 000
3 3
per m for 0.1–0.5 µm diameter particles, (2) 6000 per m for
4. Summary of Test Method
0.5–1 µm diameter particles, and (3) 100 per m for 1–5 µm
4.1 This test method uses a test characterization chamber
diameter particles; water vapor content not exceeding a vapor
system to evaluate indoor air quality particle sensors and
pressure dewpoint of 3°C; and total oil content not exceeding
sensor systems on their capabilities to detect and measure
0.01 mg/m .
particles against reference PM monitors.
3.2.5.1 Discussion—For the purposes of this standard,
4.2 PM is introduced into the test characterization
particle-negligibleairhasparticlesreducedtoconcentrationsat 2.5
chamber, and test sensors or test sensor systems are tested at
or below the limit of detection of PM mass concentration
2.5
prescribed, steady-state concentrations. The test system uses
reference monitor being used in this test method.
instruments that meet performance criteria demonstrating
3.2.6 PM ,n—particles collectable by a sampler with an
equivalence with established reference methods, along with
upper 50 % cut point of 10 µm in aerodynamic diameter, along
ancillary instruments, to evaluate the performance of the test
with other conditions as defined in the U.S. CFR Title 40, Part
sensors or test sensor systems.
58.
4.3 The test sensor’s or test sensor system’s capabilities are
3.2.7 PM ,n—particles collectable by a sampler with an
2.5
evaluated based on the following parameters: Average; Stan-
upper50%cutpointof2.5µminaerodynamicdiameter,along
dard Deviation (SD); Relative Standard Deviation (RSD);
with other conditions as defined in the U.S. CFR Title 40, Part
Bias; Precision; Intra-Model Variability (IMV); Mean Error;
58.
Pearson Linear Coefficient of Determination (R ); Climate
AvailablefromUnitedStatesEnvironmentalProtectionAgency(EPA),William
Jefferson Clinton Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20460, The boldface numbers in parentheses refer to the list of references at the end of
http://www.epa.gov. this standard.
D8405 − 21
Susceptibility; Response to Interferents; Drift (Span); Data this test method. According to Baron and Willeke (2),itis
Recovery; and Response to Loss of Power. important that as many components as possible are electrically
conductive to minimize the creation or presence of electric
5. Significance and Use
fields in the test characterization chamber that will contribute
5.1 Poorindoorairqualityhasbeenimplicatedinsignificant to particle losses due to static cling to surfaces, biasing the
adverse acute and chronic impacts on occupant health and particle concentration in the vicinity of a reference monitor
performance.Theabilitytoassessthecomponentscontributing
sampling probe or test sensor or test sensor system.
to poor indoor air quality is critical for determining best
6.2 The test system shall be capable of maintaining air
practices for improving indoor air quality.
temperature with a minimum range of 20°C to 50°C within the
5.2 Measurement of pollutants in indoor environments us-
test characterization chamber. All temperature conditions
ing sensors and sensor systems provides information needed to
tested in this standard shall be within a tolerance of 62°C. At
improve indoor air quality through pollutant source control,
a minimum, test system temperature probe(s) are calibrated at
ventilation, filtration or other treatments.
the vendor-specified frequency using standard reference mate-
5.3 Thismethodusesatestcharacterizationchambersystem
rials and shall have a minimum specified accuracy of 61.0°C.
equipped with reference monitor(s) to evaluate the response of
6.3 The test system shall be capable of generating a RH
test sensors or test sensor systems to specific types of particles
range of at least 40 % to 80 % within the test characterization
(for example, salt, polystyrene latex, or dust). To facilitate
chamber. All RH values listed in this standard shall be within
reproducible results, the test particles used within this method
a tolerance of 610 %.At a minimum, test system RH probe(s)
are standardized and have known properties. The user is
shall be calibrated at the vendor-specified frequency using
cautioned that a single particle type is not representative of all
standard reference materials and shall have a minimum speci-
particles found indoors.The relative response of test sensors or
fied accuracy of 62%.
test sensor systems to a reference monitor can vary by a factor
of two for different particle types (for example, primary or
6.4 The test system includes an instrument serving as a
secondary, organic or inorganic, outdoor or indoor origin; see
reference monitor possessing U.S. EPA performance designa-
6.11.3 for further discussion). Furthermore, the user is cau-
tionofClassIIIFEMforPM .Thereferencemonitorshallbe
2.5
tioned that the lower limit of particle size detection for optical
capable of simultaneously providing high-resolution, real-time
test sensors and test sensor systems is generally 0.3 µm in
measurements of both PM and PM . The reference monitor
10 2.5
diameter;particlesbelowthissizearegenerallyundetectedand
shall have a time resolution of 1 minute or less. The reference
may represent a significant health concern as well.
monitor sampling system shall include a particle drying system
that can remove moisture from a test characterization chamber
6. Apparatus
air sample at 50°C and 80 % RH, such that the RH of the
6.1 The test system, used for testing particle sensors and
sample is reduced to no more than 40 % at the temperature of
sensor systems, shall include a test characterization chamber.
the reference monitor measurement cell. If the reference
The test characterization chamber is composed of stainless
monitor uses optical scattering, aerodynamic time-of-flight, or
steel or an equivalently non-corrosive and electrically conduc-
electrical mobility techniques, the reference monitor manufac-
tive material. The test characterization chamber is constructed
turer shall either provide the particle density used to calculate
to be airtight in accordance with Practice D6330, such that the
particle mass, or the reference monitor shall report both
air leakage rate of the test characterization chamber at +10 Pa
particle mass and number size distributions that will allow
gauge pressure shall be less than 1 % of the air change rate
equivalent spherical particle density to be calculated.
under normal operation during sensor tests. Airtightness is
measured as follows: (1) seal the outlet(s) of the test charac-
6.5 The test system includes any number of additional
terization chamber; (2) supply air to the test characterization
instruments to act as supplementary reference monitor(s)
chamber through the inlet and adjust the airflow rate such that
capable of providing high-resolution measurements of the
the pressure difference between the inside and outside of the
particle mass size distribution over the entire particle diameter
test characterization chamber is maintained at 10 61 Pa,
range from at least 20 nm to 20 µm, if the reference monitor
measured by pressure transducer with a minimum specified
does not already possess this capability. The supplementary
accuracy of 61 Pa; and (3) measure the airflow with a device
reference monitor(s) shall have a time resolution of 5 minutes,
that has a minimum specified accuracy of 62 %. This
or less.
measured airflow is the leakage rate of the test characterization
6.6 The test system includes a dynamically controlled fan,
chamber. The minimum test characterization chamber size is
or system of fans, and any ancillary components necessary to
such that the cross-sectional area of the arrangement of
mix the air within the test characterization chamber to homo-
triplicate test sensors or test sensor systems projected onto any
geneity. Homogeneity occurs when the average PM concen-
interior face of the test characterization chamber does not
2.5
tration (n = 20), for any level specified in this test method,
exceed 15 % of the area of that interior face.
measured with the reference monitor (FEM) does not deviate
6.1.1 Discussion—Stainless steel is specified as a material
for some components in this test standard because it is by more than 62 % between the four locations where the three
test sensors and one reference monitor sampling probe are
electrically conductive and non-reactive with the substances
used, under the sensor evaluation environmental conditions, in located within the test characterization chamber. The test
D8405 − 21
system shall include dehumidification coils and heating ele- vices to hold, hang, or otherwise support test sensors or test
ments or an equivalent system capable of controlling tempera- sensor systems. The mounting devices shall be capable of
ture and RH within the specifications described in 6.2 and 6.3, supporting at least 3 test sensors or test sensor systems. The
respectively. The fan or system of fans shall be capable of mounting devices shall be positioned so that all test sensors or
moving air across the dehumidification coils and heating test sensor systems and the reference monitor(s) encounter
elements. The test system shall be equipped with at least one equivalent exposure as specified in 6.6.
particle system. An example of a test system is presented in
6.9 The reference monitor and its sampling probe shall be
Fig. 1.
connected to the test characterization chamber in a way that
6.6.1 Discussion—An example of an ancillary component
limits line losses of PM and PM by mass to a maximum of
2.5 10
used to mix the air within a test characterization chamber to
2 %. Reference monitor sampling probe materials shall consist
homogeneity is a mechanized, louvered ceiling that would
of stainless steel or conductive silicone tubing, if the instru-
assist in distributing the air from mixing fans.This test method
ment does not already include a vendor-supplied sampling
does not prescribe a mixing airflow rate or an airflow rate
probe.
through the test characterization chamber; rather, it establishes
6.10 Particle Neutralizer—A bipolar particle neutralizer is
performance parameters to ensure that the airflow is sufficient
installed in the test system downstream of the particle system
to achieve homogeneity under steady state conditions.
and upstream of the test characterization chamber. The test
6.7 To preclude infiltration of air from outside of the
characterizationchamberinteriorsurfacesandsensormounting
chamber from entering the test characterization chamber, the
devicesshallbeelectricallygroundedorprovidedwithameans
test characterization chamber shall be maintained at a positive
to discharge any charged particles present in the test charac-
air pressure with respect to the air outside of the chamber. A
terization chamber.
minimum positive space pressure of 10 Pa shall be continu-
6.10.1 Discussion—According to Baron and Willeke (2),
ously maintained throughout the test. This may be accom-
particles can possess electrostatic charges that influence their
plished by adjusting the total supply air to the test character-
movement and losses within an electric field or in the vicinity
ization chamber to exceed the total exhaust air from the
of conductive and dielectric materials. In ambient air, a very
chamber. The total exhaust air from the test characterization
small fraction of particles is electrically charged. However,
chamberincludesthesumofallairremovedfromthechamber,
aerosol nebulization or powder dispersion can generate par-
including all air sampling devices (for example, reference
ticles with a significant fraction possessing single or multiple
monitors, gravimetric PM samplers for calibrations, aerosol
2.5
charges. Removing charges from particles is important to
generators, etc.).
reduce particle loss to stray electric fields and adherence to the
6.8 Sensor Mounting Devices—The test characterization walls of the test characterization chamber or chamber
chamber shall have stainless steel or equivalently non- components, as well as ensuring unbiased measurements if a
corrosive and electrically conductive material mounting de- reference monitor uses particle electrical mobility as the
FIG. 1 Example Test System
D8405 − 21
operation principle. Commercially available particle neutraliz- ¯
Q = the average gravimetric sampler flow rate
inorganic
ers employ radionuclides, soft X-rays, or corona-discharge
during the inorganic span concentrations
methods, and can be unipolar (remove only positive or nega-
sampling period (L/min); and
tive charges) or bipolar (remove both types of charges).
t = the duration of inorganic span concentra-
span, inorganic
tion sampling period (min).
6.11 Particle Monitors:
¯
6.11.1 The reference monitor shall have a PM measure- If R is within 610%of GS , the
2.5
span, inorganic span, inorganic
ment accuracy that meets or exceeds the accuracy requirement reference monitor may proceed to the accuracy check in
¯
of the certification scheme under which it was approved. At a 6.11.2.4.If R is not within 610 % of GS -
span, inorganic s
minimum, reference monitors shall be initially calibrated at an pan, inorganic, the reference monitor shall be recalibrated in
ISO 17025 accredited facility following manufacturer guide-
accordance with 6.10.1.
lines at a frequency no less than the lesser of 12 months or the
6.11.2.4 Span Concentration with Organic Particles—The
manufacturer-recommended frequency.
PM organic particle source identified in 6.11.2 shall be
2.5
6.11.2 No more than 24 hours prior to Phase 1 of each test,
introduced into the test characterization chamber such that the
the reference monitor accuracy shall be checked using gravi-
reference monitor reports a concentration of 300 630 µg/m
metric samples from inside the test characterization chamber.
and a relative standard deviation of less than 5 % over 20
6.11.2.1 The reference monitor accuracy check shall be
consecutive measurements. When this stable condition has
conducted in accordance with EPA Method IP-10A with the
been achieved, the gravimetric sampler shall commence opera-
exceptions that a 10 L/min gravimetric sampler with a 2.5 µm
tion. Both the reference monitor and gravimetric sampler shall
size selective inlet and 37 mm polytetrafluoroethylene (PTFE)
continue to operate during this stable condition for a minimum
filters shall be used. The gravimetric sampler shall be located
of 2 hours. The average of the reference monitor concentration
near the center of the test characterization chamber and within
during the entire time period the gravimetric sampler was
¯
10 cm of the reference monitor inlet. In addition, a mass flow
operated shall be recorded as R . The concentration
span, organic
controller shall be utilized to ensure that the gravimetric
measured by the gravimetric sampler shall be recorded as
sampler flow rate is maintained at 10 60.2 L/min. ¯
GS GS and shall be calculated using the
span, organic span, organic
6.11.2.2 Zero Concentration—The inlet of the reference
following equation:
monitorshallbepresentedaconcentrationofHEPA-filteredair
m 2 m
final, organic initial, organic
that does not impact the reference monitor air sampling flow
GS µg⁄ m 5 (2)
~ !
span, organic
¯
~Q ⁄ 1000! 3t
rate. When the standard deviation of at least 20 consecutive
organic span, organic
measurements from the reference monitor is less than 0.1
where:
µg/m , the average of those measurements shall be recorded as
m = themassofthefilterattheendoftheorganic
final, organic
¯
R . The gravimetric sampler does not operate during this
zero
span concentration sampling period (µg);
zero-concentration measurement.
m = the mass of the filter at the start of the
initial, organic
6.11.2.3 Span Concentration with Inorganic Particles—The
organic span concentration sampling period
PM inorganic particle source identified in 6.11.2 shall be
2.5
(µg);
introduced into the test characterization chamber such that the
¯
Q = the average gravimetric sampler flow rate
organic
reference monitor reports a concentration of 300 630 µg/m
during the organic span concentrations sam-
and a relative standard deviation of less than 5 % over 20
pling period (L/min); and
consecutive measurements. When this stable condition has
t = the duration of organic span concentration
span, organic
been achieved, the gravimetric sampler shall commence opera-
sampling period (min).
tion. Both the reference monitor and gravimetric sampler shall
¯
If R is within 610%of GS , the refer-
span, organic span, organic
continue to operate during this stable condition for a minimum
ence monitor may proceed to the test procedures in Section 10.
of 2 hours. The average of the reference monitor concentration
¯
However, if R is not within 610%of GS ,
span, organic span, organic
during the entire time period the gravimetric sampler was
an organic calibration function shall be applied to the reference
¯
operated shall be recorded as R . The concentration
span, inorganic
monitor measurements as described in 6.11.2.5.
measured by the gravimetric sampler shall be recorded as
¯ 6.11.2.5 If the reference monitor did not satisfy the criteria
GS GS and shall be calculated using the
span, inorganic span, inorganic
in 6.11.2.4, an organic calibration function shall be created to
following equation:
correct the reference monitor measurements specifically when
m 2 m
final, inorganic initial, inorganic
3 sampling organic particles. The organic calibration shall in-
GS µg⁄ m 5 (1)
~ !
span, inorganic
3 3 3
¯
~Q ⁄ 1000! 3t clude a four-point calibration at 0 µg/m , 50 µg/m , 150 µg/m ,
inorganic span, inorganic
¯
and 300 µg/m . The reference monitor value R from
zero
where:
6.11.2.2 and a zero for the gravimetric value are used for the 0
m = the mass of the filter at the end of the
final, inorganic ¯
µg/m data point. The reference monitor value R and
span, organic
inorganic span concentration sampling pe-
gravimetric sampler value GS from 6.11.2.4 are used
span, organic
riod (µg); 3
for the 300 µg/m data point. The particle generation and
m = the mass of the filter at the start of the
initial, inorganic
measurement process described in 6.11.2.4 shall be repeated
inorganic span concentration sampling pe- 3 3
for 50 65 µg/m and 150 615 µg/m target concentrations. A
riod (µg);
simplelinearregressioncalibrationcorrectionequationshallbe
D8405 − 21
developedtocorrectallorganicparticledatafromthereference
ρ = the density of the particles, from 6.11.3.1(1),
p,actual
monitor as described in Practice E3080 where:
generated and transported into the test character-
ization chamber;
Y 5 β X1β (3)
1 0
ρ = the density of particles assumed by a reference
p,0
where:
monitor manufacturer; and
X = the set of averaged PM values (µg/m ) reported by
R = the corrected particle mass concentration value
2.5
the reference monitor at the 0, 50, 150, and 300 µg/m
observed by a reference monitor.
calibration points;
(a) Discussion—According to Baron and Willeke (2) and
Y = the set of PM values (µg/m ) reported by the gravi-
2.5
Seinfeld and Pandis (3), the principles of operation for optical
metric sampler at the 0, 50, 150, and 300 µg/m
scattering, aerodynamic time-of-flight, and electrical mobility
calibration points;
measurementsareindirectlyrelatedtothemassofparticlesand
β = regression slope; and
are therefore affected by assumed particle density values.
β = regression intercept.
Manufacturers of optical scattering, aerodynamic time-of-
Theorganiccalibrationfunctionshallonlybeusedtocorrect
flight, and electrical mobility instruments must assume a
reference monitor measurements collected during Phase 1
particle density value, in some cases to maximize correlation
testing using the PM organic particle source identified in
2.5
with ambient PM reference measurements. The particle
2.5
6.11.2, in the following manner:
density value assumed by manufacturers of optical scattering,
R 5 β R1β (4) aerodynamic time-of-flight, and electrical mobility instruments
organic 1 0
often differs greatly from the particle density values of the
where:
particlesgeneratedinthistestmethod.Therefore,theusershall
R = the reference monitor organic PM concentration
organic 2.5
correct mass concentration values reported by reference moni-
after correction against the gravimetric sampler;
tors using optical scattering, aerodynamic time-of-flight, or
R = the reference monitor organic PM concentration
2.5
electrical mobility techniques to account for either (1) the
before correction against the gravimetric sampler;
particle density value explicitly provided by the manufacturer,
β = regression slope; and
or (2) the implicit particle density value required to obtain the
β = regression intercept.
uncorrected mass concentration reported by the reference
6.11.3 Measurement Corrections:
monitor given the reported particle mass distribution.
6.11.3.1 Particle Density:
6.11.3.2 Particle Dynamic Shape Factor:
(1) The particle density values used in this test method
(1) The particle dynamic shape factor values used in this
shall be 2.65 g/cm for Arizona Test Dust Grade A4 Coarse,
test method shall be 1.5 for Arizona Test Dust Grade A4
3 3
2.17g/cm forsodiumchloride,and1.05g/cm forpolystyrene
Coarse, 1.08 for sodium chloride, and 1.0 for polystyrene latex
latex spheres.
spheres.
(2) The particle mass concentrations reported by reference
(2) The particle mass concentrations reported by reference
monitor(s) using gravimetric filter, or tapered element oscillat-
monitor(s) using optical scattering techniques shall not be
ing microbalance shall not be corrected, for the purposes of
corrected, for the purposes of evaluation parameter
evaluation parameter calculations or to account for any differ-
calculations, to account for any differences in particle dynamic
encesinparticledensityvaluesoftheparticlesgeneratedinthis
shape factor values of the particles generated in this test
test method.
method.
(a) Discussion—According to Baron and Willeke (2), the
(a) Discussion—According to Baron and Willeke (2),
principles of operation for gravimetric filter and tapered
analytical functions are lacking to adjust particle mass concen-
element oscillating microbalance particle measurements are
trations reported by optical scattering instruments to account
directly related to the mass of particles and are therefore not
for particle dynamic shape factors. More significantly, diam-
affected by assumed particle density values.
eters of irregularly shaped particles determined through optical
(3) The particle mass concentrations reported by reference
scattering techniques have been shown to be nearly identical to
monitor(s)usingopticalscattering,aerodynamictime-of-flight,
thoseofsphericalparticlesinbothlimitingcaseswhereparticle
or electrical mobility techniques shall be corrected, for the
diameter is much smaller than and much larger than the
purposes of evaluation parameter calculations, to account for
wavelength of the light source. Given the lack of analytical
any differences in particle density values of the particles
correction functions and the expected lack of meaningful bias
generated in this test method and particle density values
due to differences in dynamic shape factor of particles gener-
assumed by the reference monitor manufacturer(s). The par-
ated in this test method, correction of measurements to account
ticlemassconcentrationsshallbecorrectedusingthefollowing
for particle dynamic shape factor is not justified for optical
equation:
scattering reference monitor(s).
ρ
(3) The sample flow rates of reference monitor(s) using
p,actual
R 5 R 3 (5)
ρ
gravimetric filter or tapered element oscillating microbalance
p,0
that are preceded by a size-selective inlet, such as a cyclone or
where:
impactor, shall be adjusted, to account for any differences in
R = the uncorrected particle mass concentration value
particle dynamic shape factor and density values of the
reported by a reference monitor;
particles generated in this test method and particle dynamic
D8405 − 21
shape factor and density values assumed by the reference
D = the original extent of a particle diameter bin
p,0
monitor manufacturer(s) for proper size-selection by the inlet.
range assumed by a reference monitor manufac-
The reference monitor manufacturer(s) must be contacted to
turer;
provide the correct sample flow rates to use such that the
ρ = the density of the particles, from 6.11.3.1(1),
p,actual
size-selective inlet achieves an upper 50 % cut point of 2.5 µm generated and transported into the test charac-
in aerodynamic diameter with the particle densities in
terization chamber;
6.11.3.1(1) and the particle dynamic shape factors in ρ = the density of particles assumed by a reference
p,0
6.11.3.2(1). monitor manufacturer;
χ = the dynamic shape factor of the particles, from
(a) Discussion—According to Baron and Willeke (2), the
6.11.3.2(1), generated and transported into the
principles of operation for gravimetric filter or tapered element
test characterization chamber;
oscillating microbalance do not discriminate against particles
D = the particle diameter;
based on their size. In order to obtain a size-fractionated p
C (D ) = the Cunningham slip correction factor for the
sample, such instruments are usually preceded by an inlet that c p,adj
adjusted extent of a particle diameter bin range;
uses inertial techniques to allow only particles below a certain
C (D ) = the Cunningham slip correction factor for the
c p,0
diameter to proceed to measurement by the instrument. These
original extent of a particle diameter bin range;
inertial inlets, such as cyclones or impactors, are designed with
C (D ) = the Cunningham slip correction factor for a
c p
a certain flow rate and assumed particle dynamic shape factor
given particle diameter D ; and
p
and density values to achieve proper size discrimination.
λ = thegasmolecularmeanfreepath,whichisequal
Therefore, if the test particle dynamic shape factor and density
to 0.0665 µm for the purposes of this test
values are different from those assumed by the manufacturer,
standard.
the inlet flow rate must be adjusted to achieve the proper size
(a) Discussion—According to Baron and Willeke (2) and
discrimination. While it may be possible to calculate the
Seinfeld and Pandis (3), the Cunningham slip correction factor
maximum particle diameter actually permitted by a size-
accounts for slip flow behavior as particle size decreases and
selective inlet using the particle densities in 6.11.3.1(1) and the
the surrounding gas no longer behaves like a continuum from
particle dynamic shape factors in 6.11.3.2(1), it is usually not
the perspective of the particle.
possible for a user to correctly determine the flow rate
(5) The particle diameter bin ranges, as well as any particle
adjustment that must be made for a size-selective inlet to
mass concentrations that are calculated from particle counts
change the maximum particle diameter permitted; this is
assigned to such bins, reported by reference monitor(s) using
especially true for cyclones, which lack analytical functions to
electrical mobility techniques, shall be adjusted, to account for
describe their particle size discrimination behavior. Therefore,
any differences in particle dynamic shape factor values of the
the reference monitor manufacturer(s) shall be consulted to
particles generated in this test method and particle dynamic
obtain correct sample flow rate adjustments to change the
shape factor values assumed by the reference monitor manu-
maximum particle diameter permitted through the size-
facturer(s). In the absence of manufacturer instructions, the
selective inlet when using the particles generated in this test
extents of particle diameter bin ranges shall be adjusted using
method.
the following iterative equation:
(4) The particle diameter bin ranges, as well as any particle
mass concentrations that are calculated from particle counts D C D
~ !
p,0 c p,adj
D 5 · (8)
p,adj
assigned to such bins, reported by reference monitor(s) using χ C D
~ !
c p,0
aerodynamic time-of-flight techniques, shall be corrected in
2λ 2λ
C D 5 11 1.142 1 0.558 · exp 2 0.999 ⁄ (9)
~ ! F S S DDG
accordance with reference monitor manufacturer instructions,
c p
D D
p p
to account for any differences in particle dynamic shape factor
where:
anddensityvaluesoftheparticlesgeneratedinthistestmethod
and particle dynamic shape factor and density values assumed D = the adjusted extent of a particle diameter bin
p,adj
range, after accounting for particle dynamic
by the reference monitor manufacturer(s). In the absence of
shape factor differences;
manufacturer instructions, the extents of particle diameter bin
D = the original extent of a particle diameter bin
ranges shall be adjusted using the following iterative equation:
p,0
range assumed by a reference monitor manufac-
χρ C ~D !
p,0 c p,0 turer;
D 5 D (6)
Œ
p,adj p,0
ρ C D
~ !
χ = the dynamic shape factor of the particles, from
p,actual c p,adj
6.11.3.2(1), generated and transported into the
2λ 2λ
C ~D ! 5 11 1.142 1 0.558 · exp 2 0.999 ⁄ (7)
F S S DDG
c p
test characterization chamber;
D D
p p
D = the particle diameter;
p
where:
C (D ) = the Cunningham slip correction factor for the
c p,adj
D = the adjusted extent of a particle diameter bin
adjusted extent of a particle diameter bin range;
p,adj
range, after accounting for particle dynamic C (D ) = the Cunningham slip correction factor for the
c p,0
shape factor and density differences; original extent of a particle diameter bin range;
D8405 − 21
median diameter between 0.1 and 0.2 µm with a geometric
C (D ) = the Cunningham slip correction factor for the
c p
standard deviation between 1.5 and 1.8. The NIST Standard
original extent of a particle diameter bin range;
Reference Material 1690 polystyrene spheres shall have a
the Cunningham slip correction factor for a
certified number of average diameter and uncertainty in accor-
given particle diameter D ; and
p
dance to the NIST Certificate for Standard Reference Material
λ = thegasmolecularmeanfreepath,whichisequal
1690 Polystyrene Spheres (Nominal Diameter 1 µm). For any
to 0.0665 µm for the purposes of this test
tests employing PM particles, it shall be verified that the
standard.
2.5
majority of the PM mass from the particle system is larger
2.5
6.11.3.3 Particle Refractive Index:
than 0.3 µm in diameter, using particle mass size distribution
(1) The particle mass concentrations and any particle
data from the supplementary reference monitor(s). For tests
diameter bin ranges reported by any reference monitor(s) using
employing PM particles, it shall be verified that the majority
gravimetric filter or tapered element oscillating microbalance,
ofthePM massfromtheparticlesystemislargerthan0.3µm
optical scattering, aerodynamic time-of-flight, or electrical
in diameter, using particle mass size distribution data from the
mobility techniques shall not be corrected, for the purposes of
supplementary reference monitor(s).
evaluation parameter calculations, to account for any differ-
6.13 Particle-Negligible Air Generation System—A
ences between the refractive index of the particles generated in
particle-negligible air generation system shall be included
this test method.
which can remove pollutants and generate dry and particle-
(a) Discussion—According to Baron and Willeke (2),
negligible air for use in dilution of PM to achieve targeted
particle refractive index has no influence on the working
2.5
PM concentrations inside the test characterization chamber.
principles of reference monitor(s) using gravimetric filter,
2.5
The particle-negligible air generation system shall be capable
tapered element oscillating microbalance, aerodynamic time-
of removing particles to the lower limit of detection of the
of-flight, or electrical mobility techniques. The response from
referencemonitorbeingusedforthatparticle,bygeneratingair
optical scattering instruments is dependent on particle refrac-
satisfying ISO 8573-1 Class 2.4.1 purity requirements.
tive index. However, the refractive index of particles generated
6.13.1 The particle-negligible air generation system shall
in this test method are very similar, as they are for most
include the following components for removal of moisture and
inorganic particles, and are not expected to bias optical
particles, or an equivalent set of components able to remove
scattering measurements to a degree exceeding the measure-
particles, to the lower limit of detection of the reference
ment noise. Particle refractive index differences can signifi-
monitor.
cantly bias optical scattering measurements if the particle
6.13.1.1 Asystem capable of removing moisture and drying
composition is carbonaceous in nature, such as those associ-
test characterization chamber air to RH conditions required by
ated with smoke or soot from indoor activities like cooking;
the test method.
such particle types are not used in this test method. Finally, the
6.13.1.2 One in-line particle filter that has at least a 99.97 %
correction of an optical scattering instrument’s response to
removal efficiency of particles with a diameter of 0.3 µm. The
particleswithdifferentrefractiveindicesiscomplexandalmost
removal efficiency shall be verified by the filter meeting the
always requires intervention on the part of the reference
HEPA efficiency standard when tested in accordance with
monitor manufacturer(s) to modify the firmware of the optical
DOE-STD-3020, at an airflow rate that is no less than the
scattering instrument. Given the expected lack of meaningful
maximum airflow rate through the particle-negligible air gen-
biasduetodifferencesinrefractiveindexofparticlesgenerated
eration system that is achieved within this test method.
in this test method and the effort needed to modify the
instrument response, correction of measurements to account
6.14 Anexamplediagramofatestcharacterizationchamber
for particle refractive indices is not justified for optical
system is included in Fig. 1.
scattering reference monitor(s).
7. Hazards
6.12 Particle Systems:
7.1 Exposure to particulate matter can be a hazard;
6.12.1 Any number of particle generators or dispensers
capable of producing suspensions of particles within the therefore, the test characterization chamber shall be sealed to
limit exposure of laboratory staff to test pollutants and inter-
diameter range of at least 50 nm to 10 µm from various
powders or solutions in de-ionized water, shall be installed. ferents during testing.
Nominal PM particle sizes shall include diameters up to 2.5
2.5
7.2 Exposure to test gases can be hazardous; therefore, the
µm, as well as interferent particle sizes greater than 2.5 µm and
test characterization chamber shall be exhausted in a manner
less than or equal to 10 µm for interferent testing.
consistent with safety requirements for the disposal of test
6.12.2 The particle sources required for use in the applica-
pollutants and interferents.
tion of this test method include Arizona Test Dust Grade A4
7.3 Condensed fluids may be hazardous. Hence, the test
Coarse for interferent testing, sodium chloride for inorganic
characterization chamber shall include a drain to remove
PM generation, and NISTStandard Reference Material 1690
2.5
condensation generated during testing.
monodisperse polystyrene spheres of 1 µm nominal diameter
for organic PM generation. 7.4 In cases where radioactive elements are used in particle
2.5
6.12.3 Particle size and distribution of Arizona Test Dust neutralizers, precautions to limit radiation exposure shall be
Grade A4 Coarse is determined in accordance with ISO taken and all local, regional and national radiation safety
12103-1. Sodium chloride aerosol generated shall have a count requirements shall be followed.
D8405 − 21
8. Sampling, Test Specimens, and Test Units systems are cleaned of powder in solid particle dispensers.All
surface
...