ASTM E2931-13 (2025) PDF

Full title and description

ASTM E2931-13(2025) — Standard Test Method for Limiting Oxygen (Oxidant) Concentration of Combustible Dust Clouds. This ASTM test method specifies a laboratory procedure for determining the limiting oxygen concentration (LOC) of dispersed combustible dust clouds in a near‑spherical closed vessel (20 L or larger) when air is progressively diluted with an inert/nonflammable gas. Results are used to characterize relative deflagration behavior and to inform inerting and process‑safety decisions.

Abstract

This standard describes a repeatable laboratory technique to measure the lowest oxygen (oxidant) concentration at which a given dispersed dust cloud will propagate a flame (the LOC). Tests are performed in a closed chamber (commonly a 20‑L sphere or larger), typically using a pyrotechnic ignitor (recommended 2500‑J for 20‑L tests) and defined sample dispersion/particle size conditions. The LOC values are method‑ and sample‑dependent and are intended as comparative deflagration parameters to support process safety, inerting strategies and pneumatic‑transport assessments rather than as absolute intrinsic material constants.

General information

• Status: Active / Current (reissued 2025).
• Publication date: October 1, 2025 (designation ASTM E2931-13(2025)).
• Publisher: ASTM International.
• ICS / categories: 13.230 — Explosion protection (dust explosion testing & prevention).
• Edition / version: Designation ASTM E2931-13 with reapprovals/amendments noted (original 2013; reapproved 2019; reissued/confirmed 2025 as ASTM E2931-13(2025)).
• Number of pages: 9 pages.

Scope

This test method is intended to determine the limiting oxygen (oxidant) concentration of a combustible dust dispersed in a mixture of air and an inert/nonflammable gas in a near‑spherical closed vessel of 20 L or greater volume. Data from this method provide a relative measure of the deflagration characteristics of dust clouds and are suitable for use in process safety decisions (for example, design of inerting systems and safe operating envelopes). The method is not a direct measure of full‑scale fire hazard; results must be used together with broader risk assessments and appropriate safety practices.

Key topics and requirements

• Definition and determination of limiting oxygen concentration (LOC) for dispersed dust clouds.
• Use of a near‑spherical closed vessel (20‑L chamber commonly specified; larger chambers may also be used for comparison).
• Recommended ignition source for 20‑L tests: 2500‑J pyrotechnic ignitor (composition and energy specified in the method).
• Control of sample dispersion, particle size distribution and concentration — LOC values are sample‑ and method‑dependent.
• Test procedure for progressive dilution of oxygen with an inert gas and observation of flame propagation/no‑propagation endpoint.
• Guidance on interpretation: LOC as a relative deflagration parameter (not a complete fire/hazard rating alone).
• Safety, handling and precautionary notes required when testing combustible dusts.

Typical use and users

Used by industrial safety engineers, laboratory technicians, combustible‑dust researchers, process designers and consultants, manufacturers of powders and granular materials, and organizations responsible for pneumatic transport or dust handling systems. Typical applications include specifying inerting concentrations for process vessels, evaluating suitability of inert gases for explosion prevention, researching dust flammability properties, and supporting regulatory or internal safety programs for combustible dust control.

Related standards

Standards commonly referenced alongside ASTM E2931 include EN 14034‑4 (European method for LOC determination in 20‑L chambers), ASTM test methods that characterize dust deflagration behavior (for example, methods for pressure and rate‑of‑pressure‑rise testing), NFPA guidance and codes on combustible dust (for example NFPA 652, NFPA 68), and other national/international test methods addressing dust explosion testing and mitigation. The document is developed under ASTM Committee E27 (subcommittee E27.05) and is typically used in combination with complementary ASTM and NFPA standards when assessing dust explosion risk.

Keywords

limiting oxygen concentration, LOC, combustible dust, dust cloud, inerting, dust explosions, deflagration parameters, 20‑L chamber, pyrotechnic ignitor, explosion protection, ASTM E2931

FAQ

Q: What is this standard?

A: ASTM E2931-13(2025) is a laboratory test method that determines the limiting oxygen (oxidant) concentration at which a dispersed combustible dust cloud will sustain flame propagation. It provides a controlled procedure to obtain LOC values used in evaluating inerting and explosion‑prevention strategies.

Q: What does it cover?

A: It covers test apparatus, sample preparation and dispersion, ignition sources (commonly a 2500‑J pyrotechnic ignitor for 20‑L tests), the progressive dilution procedure with an inert gas to determine the oxygen level below which ignition does not propagate, and guidance on interpreting results and safety precautions. It specifies use of a near‑spherical closed vessel of 20 L or larger.

Q: Who typically uses it?

A: Process safety engineers, dust explosion researchers, testing laboratories, material manufacturers, regulatory compliance staff, and consultants who evaluate and design inerting or mitigation systems for dust handling and processing equipment.

Q: Is it current or superseded?

A: As designated ASTM E2931-13(2025), this test method is shown as current/active (reissued in 2025). The original was issued in 2013 and was reapproved/reissued subsequently; users should verify the edition in their jurisdiction and check for any later amendments before relying on it for regulatory or contractual purposes.

Q: Is it part of a series?

A: Yes. This test method is produced under ASTM Committee E27 (fire and explosion standards), subcommittee E27.05, and is used in conjunction with other ASTM and international standards that address dust explosion testing and protection (for example EN 14034‑4, ASTM methods for pressure/rate‑of‑pressure rise, and NFPA combustible dust documents).

Q: What are the key keywords?

A: Limiting oxygen concentration (LOC), combustible dust, dust cloud, inerting, dust explosions, 20‑L chamber, pyrotechnic ignitor, deflagration parameters, explosion protection.