ASTM D7651-17

Standard Test Method for Gravimetric Measurement of Particulate Concentration of Hydrogen Fuel

SIGNIFICANCE AND USE
5.1 Low operating temperature fuel cells such as proton exchange membrane fuel cells (PEMFCs) require high purity hydrogen for maximum material performance and lifetime. Measurement of particulates in hydrogen is necessary for assuring a feed gas of sufficient purity to satisfy fuel cell and internal combustion system needs as defined in SAE J2719. The particulates in hydrogen fuel for fuel cell vehicles (FCV) and gaseous hydrogen powered internal combustion engine vehicles may adversely affect pneumatic control components, such as valves, or other critical system components. Therefore, the concentration of particulates in the hydrogen fuel should be limited as specified by ISO 14687-2, SAE J2719, or other hydrogen fuel quality specifications.  
5.2 Although not intended for application to gases other than hydrogen fuel, techniques within this test method can be applied to gas samples requiring determination of particulate concentration.
SCOPE
1.1 This test method is primarily intended for gravimetric determination of particulate concentration in hydrogen intended as a fuel for fuel cell or internal combustion engine powered vehicles. This test method describes operating and quality control procedures required to obtain data of known quality satisfying the requirements of SAE J2719. This test method can be applied to other gaseous samples requiring determination of particulates provided the user’s data quality objectives are satisfied.  
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 and health 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-Oct-2017
• ICS: 27.075 - Hydrogen technologies
• Technical Committee: D03 - Gaseous Fuels
• Drafting Committee: D03.14 - Hydrogen and Fuel Cells

Relations

• Refers: ASTM E617-23 - Standard Specification for Laboratory Weights and Precision Mass Standards
• Effective Date: 15-Aug-2023
• Refers: ASTM D4150-19 - Standard Terminology Relating to Gaseous Fuels
• Effective Date: 15-Dec-2019
• Refers: ASTM E617-18 - Standard Specification for Laboratory Weights and Precision Mass Standards
• Effective Date: 01-Oct-2018
• Refers: ASTM D4150-08(2016) - Standard Terminology Relating to Gaseous Fuels
• Effective Date: 01-Jul-2016
• Refers: ASTM D7650-10 - Standard Test Method for Test Method for Sampling of Particulate Matter in High Pressure Hydrogen used as a Gaseous Fuel with an In-Stream Filter
• Effective Date: 01-Jul-2010
• Refers: ASTM E617-97(2008) - Standard Specification for Laboratory Weights And Precision Mass Standards
• Effective Date: 01-Dec-2008
• Refers: ASTM D4150-08 - Standard Terminology Relating to Gaseous Fuels
• Effective Date: 01-Dec-2008
• Refers: ASTM D4150-03 - Standard Terminology Relating to Gaseous Fuels
• Effective Date: 10-Aug-2003
• Refers: ASTM D4150-00 - Standard Terminology Relating to Gaseous Fuels
• Effective Date: 10-Jun-2000
• Refers: ASTM E617-97(2003) - Standard Specification for Laboratory Weights And Precision Mass Standards
• Effective Date: 10-Nov-1997
• Refers: ASTM E617-97 - Standard Specification for Laboratory Weights And Precision Mass Standards
• Effective Date: 10-Nov-1997

Overview

ASTM D7651-17 is an international standard developed by ASTM International that defines a gravimetric test method for measuring the particulate concentration in hydrogen fuel. This method ensures hydrogen fuel used in fuel cell vehicles (FCVs) and internal combustion engine powered vehicles meets stringent purity requirements, helping to prevent contamination that can adversely affect advanced fuel cell and internal combustion technologies. The standard is primarily referenced for quality assurance in hydrogen fueling applications, as aligned with SAE J2719, ISO 14687-2, and other recognized fuel quality standards. It can also be applied to other gases if data quality objectives are met.

Key Topics

• Purpose: The test method determines the mass concentration of particulate matter in hydrogen fuels, which is critical for safeguarding sensitive components in PEM fuel cells and hydrogen-powered vehicles.
• Measurement Approach: Utilizes precision gravimetric analysis of high-efficiency PTFE filters before and after hydrogen gas sampling.
• Clean Handling Requirements: Procedures emphasize strict avoidance of sample contamination using glove boxes, clean rooms, HEPA filtration, and anti-static tools.
• Calibration & Control: Frequent calibration and quality control of analytical balances are required to ensure measurement accuracy.
• Sample Conditioning: Both pre- and post-sampling conditioning of filters in controlled environments help maintain consistent and reliable results.
• Reporting: Results are reported in micrograms per liter (μg/L) and milligrams per kilogram (mg/kg) of hydrogen, fulfilling the reporting standards of hydrogen quality specifications.

Applications

ASTM D7651-17 is designed for a range of critical applications in hydrogen energy infrastructure:

• Fuel Cell Vehicles (FCVs): Ensures hydrogen supplied to vehicles meets strict particulate limits, prolonging the performance and reliability of PEMFCs.
• Hydrogen-Powered Internal Combustion Engines: Protects vital pneumatic and engine components from particulate-induced damage.
• Hydrogen Dispensing Stations: Used as a standard operating procedure for quality control during dispensing at fueling stations, supporting regulatory compliance.
• Research and Development: Applied in laboratory settings to validate hydrogen purity for prototype fuel cell systems.
• Regulatory Compliance: Supports industry compliance with international regulations such as SAE J2719, ISO 14687-2, and relevant government requirements.
• Gas Quality Control: The method can be adapted for particulate analysis in other high-purity gas streams where similar data quality standards are required.

Related Standards

ASTM D7651-17 references and aligns closely with several related standards to ensure comprehensive hydrogen quality assessment:

• SAE J2719: Hydrogen Quality Guideline for Fuel Cell Vehicles - outlines specific impurity limits, including particulates.
• ISO 14687-2: Hydrogen fuel - Product specification, especially for PEM fuel cells in road vehicles.
• ASTM D4150: Terminology relating to gaseous fuels.
• ASTM D7650: Test method for sampling of particulate matter in high-pressure hydrogen gas using in-stream filters.
• SAE J2600: Compressed hydrogen surface vehicle refueling connection devices - an important reference for sampling at fueling station interfaces.
• California Code of Regulations, Title 4, Division 9, Chapter 6, Article 8, Sections 4180–4181: Pertains to hydrogen fuel sampling and quality control requirements.

Practical Value

Implementing the procedures and controls in ASTM D7651-17 helps hydrogen suppliers, fuel station operators, and vehicle OEMs:

• Minimize risks associated with particulate contamination in hydrogen fuel.
• Ensure long-term reliability and performance of hydrogen-powered vehicles and systems.
• Demonstrate compliance with vital industry and regulatory standards for hydrogen purity.
• Enhance customer confidence in hydrogen as a safe and effective fuel alternative.

Keywords: ASTM D7651-17, hydrogen fuel purity, gravimetric analysis, particulate concentration, PEM fuel cell, hydrogen fuel cell vehicle, fuel quality standards, hydrogen sampling, SAE J2719, ISO 14687-2.

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: D7651 − 17
Standard Test Method for
Gravimetric Measurement of Particulate Concentration of
Hydrogen Fuel
This standard is issued under the fixed designation D7651; 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 2.2 SAE Standards:
SAE J2600 Compressed Hydrogen Surface Vehicle Refuel-
1.1 This test method is primarily intended for gravimetric
ing Connection Devices
determination of particulate concentration in hydrogen in-
SAE J2719 Hydrogen Quality Guideline for Fuel Cell Ve-
tended as a fuel for fuel cell or internal combustion engine
hicles
powered vehicles. This test method describes operating and
2.3 Other Standards:
quality control procedures required to obtain data of known
Code of Federal Regulations, Title 40, Part 50, Appendix L,
quality satisfying the requirements of SAE J2719. This test
Section 8.2
method can be applied to other gaseous samples requiring
ISO 14687–2 Hydrogen fuel -- Product specification -- Part
determination of particulates provided the user’s data quality
2: Proton exchange membrane (PEM) fuel cell applica-
objectives are satisfied.
tions for road vehicles
1.2 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
3. Terminology
standard.
3.1 Acronyms:
1.3 This standard does not purport to address all of the
3.1.1 FCV—Hydrogen Fuel Cell Vehicle
safety concerns, if any, associated with its use. It is the
3.1.2 HEPA—High Efficiency Particulate Air
responsibility of the user of this standard to establish appro-
3.1.3 PEM—Polymer Electrolyte Membrane, also called
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use. Proton Exchange Membrane
1.4 This international standard was developed in accor-
3.1.4 PEMFC—Proton Exchange Membrane Fuel Cell
dance with internationally recognized principles on standard-
3.1.5 PTFE—Polytetrafluoroethylene
ization established in the Decision on Principles for the
3.1.6 SAE—SAE International
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
3.2 Definitions: For definitions of general gaseous fuel
Barriers to Trade (TBT) Committee.
terms used in this practice, refer to D4150.
3.2.1 weight monitoring filter, WMF—This filter is put
2. Referenced Documents
inside the glove box or clean room (7.3) with the balance (7.1)
2.1 ASTM Standards: and never removed. The weight of this filter is always
measured before and after each measurement event.
D4150 Terminology Relating to Gaseous Fuels
D7650 Practice for Sampling of Particulate Matter in High
4. Summary of Test Method
Pressure Gaseous Fuels with an In-Stream Filter
E617 Specification for Laboratory Weights and Precision
4.1 This test method is used to determine the concentration
Mass Standards
of particulate matter and nonvolatile reside on filters collected
from hydrogen fuel or other gaseous streams at fueling station
dispenser nozzles (Test Method D7650, SAE J2600) or other
This test method is under the jurisdiction of ASTM Committee D03 on Gaseous
Fuels and is the direct responsibility of Subcommittee D03.14 on Hydrogen and
Fuel Cells.
Current edition approved Nov. 1, 2017. Published December 2017. Originally Available from SAE International (SAE), 400 Commonwealth Dr., Warrendale,
approved in 2010. Last previous edition approved in 2010 as D7651–10. DOI: PA 15096-0001, http://www.sae.org.
10.1520/D7651–17. Available from Office of the Federal Register, 800 N. Capitol St., NW Suite 700
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Washington, DC 20001.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Available from International Organization for Standardization (ISO), 1, ch. de
Standards volume information, refer to the standard’s Document Summary page on la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http://
the ASTM website. www.iso.ch.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7651 − 17
gaseous fuel delivery system dispenser interfaces. The particu- particulates from ambient air, the balance must be placed inside
8,7
late concentration is determined by dividing the particulate a glove box or clean room with a HEPA air filter.
weight, which is the difference of filter weights before and after
7.2 Calibration Weight–ASTM Class 1 (E617)—Category
sampling, by the total volume of hydrogen or other gaseous
calibration weights with a tolerance of 6 0.01 mg certified as
fuels passing through the filter. Every precaution should be
traceable to a national metrology institute (NMI) such as NIST
taken to avoid contamination of particulates onto the filter
mass standards should be used. The weights used for calibra-
coming from the particulate sampling adapter, the analytical
tion are 0.05 g and 0.2 g, of corrosion-resistant construction.
system, ambient air, filter handling, or other environmental
Calibration weights are to be certified on an annual basis.
sources.
7.3 Glove Box (Option A)—A glove box is a sealed chamber
that, in this application, allows weight measurements to be
5. Significance and Use
taken without particulate contamination from ambient air. Two
5.1 Low operating temperature fuel cells such as proton
gloves are built into the front side of the glove box so that the
exchange membrane fuel cells (PEMFCs) require high purity
user can place their hands into the gloves and perform weight
hydrogen for maximum material performance and lifetime.
measurements, install filters, and assemble the filter holders. A
Measurement of particulates in hydrogen is necessary for
side evacuation port or antechamber should also be used to
assuring a feed gas of sufficient purity to satisfy fuel cell and
minimize contamination of the glove box environment. The
internal combustion system needs as defined in SAE J2719.
glove box must be kept clean at all times and any visual
The particulates in hydrogen fuel for fuel cell vehicles (FCV)
particulate matter must be removed immediately. The glove
and gaseous hydrogen powered internal combustion engine
box should have a steady flow of clean, dry nitrogen (N ) at all
vehicles may adversely affect pneumatic control components,
times. The temperature and humidity should be kept consistent
such as valves, or other critical system components. Therefore,
at 21 6 2 °C and 35 6 5% RH and should be monitored by a
the concentration of particulates in the hydrogen fuel should be
data logger or other device installed in the glove box.
limited as specified by ISO 14687-2, SAE J2719, or other
7.4 Clean Room (Option B)—Analysis should occur in a
hydrogen fuel quality specifications.
climate-controlled, draft-free room constantly under positive
5.2 Although not intended for application to gases other
pressure. The relative humidity must be maintained at 35 6 5%
than hydrogen fuel, techniques within this test method can be
and the temperature must be maintained at 21 6 2 °C. If the
applied to gas samples requiring determination of particulate
temperature or humidity falls out of range, no weighing can
concentration.
occur for 24 h. Before entering the clean room, the analyst
must step on “sticky” floor mats to remove any particulate
6. Interferences
matter from the bottoms of shoes. The room must have a HEPA
6.1 Particulate matter on the filter from sources other than
air filter on the inlet air system to remove particulates from the
the hydrogen fuel will interfere with the determination of
air.
particulate concentration. Every precaution should be taken to
7.5 Static Charge Removal Device—A static charge removal
avoid contamination of particulates onto the filter from the
device, such as an ionization bar, must be placed inside the
particulate sampling adapter, the analytical system, ambient air,
glove box or clean room (7.3) next to the balance. The static
filter handling, or other environmental sources.
charge on the materials, such as weights and filters, must be
6.2 To minimize contamination on the
...

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: D7651 − 10 D7651 − 17
Standard Test Method for
Gravimetric Measurement of Particulate Concentration of
Hydrogen Fuel
This standard is issued under the fixed designation D7651; 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 is primarily intended for gravimetric determination of particulates particulate concentration in hydrogen
intended as a fuel for fuel cell or internal combustion engine powered vehicles. This test method describes operating and quality
control procedures required to obtain data of known quality satisfying the requirements of SAE J2719 and the California Code of
Regulations, Title 4, Division 9, Chapter 6, Article 8, Sections 4180 – 4181. The levels of precision and accuracy stated. J2719.
This test method can be applied to other gaseous samples requiring determination of particulates provided the user’s data quality
objectives are satisfied.
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 and health 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:
D4150 Terminology Relating to Gaseous Fuels
D7650 Test Method for Sampling of Particulate Matter in High Pressure Hydrogen used as a Gaseous Fuel with an In-Stream
Filter
E617 Specification for Laboratory Weights and Precision Mass Standards
2.2 SAE Standards:
SAE J2719 Hydrogen Quality Guideline for Fuel Cell Vehicles, April 2008
SAE J2600 Compressed Hydrogen Surface Vehicle Refueling Connection Devices
SAE J2719 Hydrogen Quality Guideline for Fuel Cell Vehicles
2.3 Other Standards:
California Code of RegulationsFederal Regulations, , Title 4, Division 9, Chapter 6, Article 8, Sections 4180 – 4181Title 40, Part
50, Appendix L, Section 8.2
ISO 1468714687–2 Hydrogen fuel -- Product specification -- Part 1: All applications except proton 2: Proton exchange
membrane (PEM) fuel cell applications for road vehicles
3. Terminology
3.1 Acronyms:
3.1.1 FCV—Hydrogen Fuel Cell Vehicle
This test method is under the jurisdiction of ASTM Committee D03 on Gaseous Fuels and is the direct responsibility of Subcommittee D03.14 on Hydrogen and Fuel
Cells.
Current edition approved July 1, 2010Nov. 1, 2017. Published August 2010December 2017. Originally approved in 2010. Last previous edition approved in 2010 as
D7651–10. DOI: 10.1520/D7651–10.10.1520/D7651–17.
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 SAE International (SAE), 400 Commonwealth Dr., Warrendale, PA 15096-0001, http://www.sae.org.
Available from Office of Administrative Law 300 Capitol Mall, Suite 1250 Sacramento, CA 95814-4339the Federal Register, 800 N. Capitol St., NW Suite 700
Washington, DC 20001.
Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http://www.iso.ch.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7651 − 17
3.1.2 PSA—HEPA—Particulate sampling adapter for sampling particulate in hydrogen fuel. High Efficiency Particulate Air
3.1.3 PEM—Polymer Electrolyte Membrane, also called Proton Exchange Membrane
3.1.4 PEMFC—Proton Exchange Membrane Fuel Cell
3.1.5 PTFE—Polytetrafluoroethylene
3.1.6 SAE—Society of Automotive EngineeringSAE International
3.2 Definitions:
3.2.1 contaminant—impurity that adversely affects the components within the fuel cell system or the hydrogen storage system
3.2.2 density—Mass per unit of volume of the fuel gas or air being considered.
3.2.3 fuel cell hydrogen—hydrogen satisfying the specifications in SAE J2719.For definitions of general gaseous fuel terms used
in this practice, refer to D4150.
3.2.1 weight monitoring filter, WMF—This filter is put inside the glove box or clean room (7.3) with the balance (7.1) and not
removed from the glove box (never removed. 7.3). The weight of this filter is always measured before and after each measurement
event.
3.3 SAE J2719—Informational Report on the development of a hydrogen quality guideline for fuel cell vehicles. This report
specifies PEM FCV hydrogen fuel quality from the fueling nozzle.
3.4 SAE J2600 Compressed Hydrogen Surface Vehicle Refueling Connection Devices—This document specifies the design
requirements for nozzles and receptacles used in high pressure hydrogen applications such as delivery from a fueling station to a
FCV
4. Summary of Test Method
4.1 This procedure is for the weight determination of filters before and after collection of particulates contained withintest
method is used to determine the concentration of particulate matter and nonvolatile reside on filters collected from hydrogen fuel
or other gaseous streams at fueling station dispenser nozzles (Test Method D7650, SAE J2600) or other gaseous fuel delivery
system dispenser interfaces. The particulate concentration is determined by dividing the particulate weight, which is the difference
of filter weights before and after sampling, by the total volume of hydrogen or other gaseous fuelfuels passing through athe filter.
Every precaution should be taken to avoid contamination of particulates 10 μm or larger onto the filter coming from the PSA,
particulate sampling adapter, the analytical system, ambient air, filter handling, or other environmental sources.
5. Significance and Use
5.1 Low operating temperature fuel cells such as proton exchange membrane fuel cells (PEMFCs) require high purity hydrogen
for maximum material performance and lifetime. Measurement of particulates in hydrogen is necessary for assuring a feed gas of
sufficient purity to satisfy fuel cell and internal combustion system needs as defined in SAE J2719. The particulates in hydrogen
fuel for FCVs fuel cell vehicles (FCV) and gaseous hydrogen powered internal combustion engine vehicles may adversely affect
pneumatic control components, such as valves, or other critical system components. Therefore, the concentration of particulates
in the hydrogen fuel should be limited as specified by ISO 14687,14687-2, SAE J2719, or other hydrogen fuel quality
specifications.
5.2 Although not intended for application to gases other than hydrogen fuel, techniques within this test method can be applied
to gas samples requiring determination of particulate matter.concentration.
6. Interferences
6.1 Particulate matter 10 μm or larger originating in the environment or equipmenton the filter from sources other than the
hydrogen fuel will interfere with the determination of total particulate matter collected on the filter. particulate concentration. Every
precaution should be taken to avoid contamination of particulates 10 μm or larger onto the filter coming from the PSA, particulate
sampling adapter, the analytical system, ambient air, filter handling, or other environmental sources.
6.2 To minimize contamination ofon the filters from body moistureoils and oils,moisture, wear powder-free gloves while
handling filters outside of the glove box.filters.
6.3 Moisture content Humidity may affect polytetrafluoroethylene (PTFE) filter weight, even though the polytetrafluoroethylene
(PTFE) filter is hydrophobic. weight. Filters should be equilibrated for a minimum of 24 h hours (h) in a controlled environment
prior to weighing. For reference, U.S. EPA filter conditioning requirements for PM10 samples are a temperature range of 25 °C
(6 3 °C) 21 6 2 °C and a humidity range of 20 to 30% RH (6 5% RH).35 6 5% relative humidity (RH).
D7651 − 17
7. Apparatus
7.1 Balance—The balance must measure to 10-5 g. The balance shouldhave a readability of 0.01 milligrams (mg). The balance
6,7
may have the capability to downloadrecord the weight measurement and calibration data into Microsoft Excel, , or a similar
program, for weight recording and calibration. program. In order to prevent contamination of particulates from ambient air, the
8,7
balance must be placed inside a glove box in a small confined or clean room with a HEPA air cleaner.filter.
7.2 Calibration weight–Class Weight–ASTM Class 1 (Class (E617S)—)—categoryCategory calibration weights with a tolerance
of 6 0.1 mg.0.01 mg certified as traceable to NIST mass standards. a national metrology institute (NMI) such as NIST mass
standards should be used. The weights used for calibration are a 0.05 g and 0.2 g weight, g, of corrosion-resistant construction.
Calibration weight isweights are to be certified on an annual basis. The weight of the particular 0.2μm polytetrafluoroethylene
(PTFE) filter used in this method test was around 0.1g.
7.3 Glove box—Box (Option A)—A glove box is a sealed containerchamber that, in this application, is designed to allow weight
measurement by balance allows weight measurements to be taken without particulate contamination from ambient air. Two gloves
are generally built into the front sidesside of the glove box with entry arranged in such a way so that the user can place their hands
into the gloves and perform weight measurement,measurements, install filters, and assemble the filter holder inside the box.
holders. A side evacuation port or antechamber should also be used to minimize contamination of the glove box environment. The
glove box must be maintainedkept clean at all times and any visual particulate matter must be removed immediately. A HEPA
vacuum can be used for cleaning purposes. A side evacuation port or anti-chamber should also be used to minimize contaminating
the glove box environment. The glove box should be flushed have a steady flow of clean, dry nitrogen (N at all times with clean
dry N2 maintaining a RH of 30% or less inside the glove box as determined ) at all times. The temperature and humidity should
be kept consistent at 21 6 2 °C and 35 6 5% RH and should be monitored by a data logger or other device installed in the glove
box.
7.4 Clean Room (Option B)—Analysis should occur in a climate-controlled, draft-free room constantly under positive pressure.
The relative humidity must be maintained at 35 6 5% and the temperature must be maintained at 21 6 2 °C. If the temperature
or humidity falls out of range, no weighing can occur for 24 h. Before entering the clean room, the analyst must step on “sticky”
floor mats to remove any particulate matter from the bottoms of shoes. The room must have a HEPA air filter on the inlet air system
to remove particulates from the air.
7.5 Static Cha
...