Overview
ISO 9038:2025 - Determination of sustained combustibility of liquids - specifies a laboratory procedure to decide whether a liquid that is classed as flammable by its flash point will sustain combustion at specified temperatures (up to 100 °C). The test is intended as a supplementary assessment to flash‑point methods and is applicable to paints (including water‑borne), varnishes, paint binders, solvents, petroleum and related products, and adhesives. It is not intended for assessing fire hazards of painted surfaces.
Key Topics and Requirements
- Purpose: Determine if vapour from a test portion ignites and continues to burn for at least 15 s after the ignition source is removed (definition of sustained combustibility).
- Test temperatures: Up to 100 °C; when no temperature is specified test at 60.5 °C and 75.0 °C (per transport/regulatory practice).
- Sample size & handling: Small test portion (typically 2.00 ml) and representative sampling in accordance with ISO 1513, ISO 15528, ISO 3170 or ISO 3171 as applicable. For petroleum products a representative sample of at least 50 ml is recommended for storage prior to testing.
- Apparatus: Combustibility tester with:
- Test cup and electrical heater capable of maintaining temperature within ±0.5 °C (≤100 °C).
- Gas ignitor with flame width 4.0 mm ± 0.5 mm and gas‑jet height 2.2 mm ± 0.1 mm above the cup.
- Temperature measuring device (resolution recommended 0.1 °C, accuracy ±0.5 °C), barometer (accuracy ±0.5 kPa), syringe accurate to ±0.05 ml, stopwatch for timed intervals.
- Verification & calibration: Apparatus performance and measuring devices to be verified at least every 12 months (Annex B), and tests done in a draught‑free area with a draught shield.
- Safety note: The method involves hazardous operations-users must apply appropriate safety precautions.
Applications and Users
ISO 9038:2025 is used by:
- Test laboratories performing regulatory compliance testing for storage, transport and classification.
- Manufacturers of paints, varnishes, solvents, adhesives, lubricants and petroleum products assessing fire risk beyond flash‑point classification.
- Regulatory bodies and compliance teams applying derogations in national/international hazardous goods regulations (e.g., UN transport recommendations, GHS‑derived rules) where demonstration of non‑sustained combustibility is required.
- R&D and quality assurance groups evaluating formulation changes that affect vapour‑phase flammability.
Related Standards
- ISO 1513 - Preparation of paint test samples
- ISO 15528 - Sampling for paints and varnishes
- ISO 3170 / ISO 3171 - Sampling of petroleum liquids
- United Nations Recommendations on the Transport of Dangerous Goods and the Globally Harmonized System (GHS) - referenced for regulatory temperature points
Keywords: ISO 9038:2025, sustained combustibility, flash point, combustibility tester, paints, solvents, petroleum, flammable liquids, test method, regulatory compliance.
