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.