ISO 9038:2021

Overview

ISO 9038:2021 - "Determination of sustained combustibility of liquids" is an ISO test method used to determine whether a liquid that is classified as flammable by its flash point will sustain combustion at a specified test temperature (up to 100 °C). The standard is intended as a complement to flash‑point testing and is used in regulatory, transport and safety assessments where some regulations permit a derogation if a product cannot sustain combustion.

Key features:

• Applicable to paints (including water‑borne), varnishes, binders, solvents, petroleum products and adhesives with a flash point.
• Not applicable to painted surfaces for fire hazard assessment.
• Rapid small‑sample procedure (test portion typically 2 ml).
• Aligned with UN Test L.2 and compatible with GHS/transport regulations (test temperatures commonly specified as 60.5 °C and 75.0 °C).

Key topics and technical requirements

• Definition of sustained combustibility: vapour ignites and continues to burn for at least 15 s after the ignition source is removed.
• Test sequence: equilibrium (30 s or 60 s at test temperature), ignition in “test” position for 15 s, then ignition source moved to “off” and observation for a further 15 s.
• Test temperatures: up to 100 °C; if unspecified, 60.5 °C and 75.0 °C are recommended.
• Apparatus & control: combustibility tester with electrical heater; heater control must maintain cup temperature within ±0.5 °C (for ≤100 °C).
• Ignition/gas jet geometry: jet centre 2.2 mm ± 0.1 mm above cup top; flame width 4.0 mm ± 0.5 mm.
• Instrumentation: temperature probe accuracy ±0.5 °C (resolution 0.5 °C or preferably 0.1 °C); barometer absolute pressure accuracy 0.5 kPa.
• Sampling & handling: follow ISO sampling standards; store samples to prevent vapour loss; ensure sample is at least 10 °C below the selected test temperature before taking test portions.
• Quality control: apparatus verification and reference materials at least annually; the third edition introduced triplicate testing as the default.

Applications and who uses this standard

ISO 9038:2021 is used by:

• Industrial and commercial laboratories performing fire‑hazard assessments.
• Paints, coatings and adhesive manufacturers for product safety data and regulatory classification.
• Petroleum and chemical producers for transport and storage hazard evaluation.
• Regulatory bodies, transport authorities and compliance specialists applying GHS, UN transport rules and national regulations that permit derogations based on sustained combustibility.
• Safety engineers and risk assessors for storage, handling and emergency planning.

Related standards

• ISO 1513 - preparation of paint test samples
• ISO 15528 - sampling of paints and varnishes
• ISO 3170 / ISO 3171 - sampling of petroleum liquids
• UN Test L.2 and GHS guidance (referenced for transport/classification alignment)

Keywords: ISO 9038, sustained combustibility, flash point, flammable liquids, combustibility tester, UN Test L.2, GHS, fire hazard assessment, flammability testing.