Overview
ISO 6925:1982 specifies a controlled laboratory method - the methenamine tablet test - for assessing the burning behaviour of textile floor coverings in a horizontal position at ambient temperature. The method applies to all types of textile floor coverings regardless of construction or fibre composition and may be used on unfinished material (with the caveat that results for unfinished specimens do not necessarily reflect in-use behaviour).
The test is intended for material comparison, acceptance testing and quality control, not for predicting performance in full-scale fires or other orientations (vertical use is outside the method's scope).
Key Topics
- Principle: Exposure of a horizontal specimen to a single methenamine tablet ignition source and measurement of resulting damaged length.
- Specimens: At least eight specimens, each 230 ± 3 mm square, sampled and cut in accordance with ISO 1957.
- Conditioning: Standard conditioning at 20 ± 2 °C and 65 ± 2 % RH (ISO 139) or oven-dry conditioning at 105 ± 2 °C for 2 h followed by desiccation.
- Apparatus (examples specified in the standard):
- Test box internally 300 mm × 300 mm × 300 mm made of hard, fire-resistant insulation board with removable flat base.
- Square metal plate (230 mm × 230 mm, 6.5 ± 0.5 mm thick) with a 205 mm diameter hole.
- Methenamine tablets (hexamethylenetetramine) flat, mass 150 ± 5 mg, diameter 6 mm.
- Desiccator, ventilated oven, vacuum cleaner, glove and laboratory fume hood.
- Procedure highlights:
- Place specimen flat, covering the test box floor, with face upward; align metal plate over specimen.
- Place and ignite the methenamine tablet centrally; allow flame/glow to burn until extinction or until it reaches the edge of the hole in the metal plate.
- Measure maximum damaged distance from the specimen centre to the damaged edge to the nearest millimetre.
- Optionally record time to flame spread to the plate hole edge.
Applications
- Acceptance testing: Widely used in trade for batch acceptance when combined with an appropriate sampling plan (e.g., ISO 2859).
- Quality control: Comparative testing of carpet and other textile floor covering materials.
- Material comparison: Evaluating the relative superficial burning behaviour of alternative constructions or fibre compositions under controlled conditions.
Note: The method evaluates superficial burning behaviour under laboratory conditions only and should not be used to assess overall fire hazard in real fires.
Related Standards
- ISO 139 - Textiles: standard atmospheres for conditioning and testing.
- ISO 1957 - Machine-made textile floor coverings: sampling and cutting specimens for tests.
- ISO 2859 - Sampling procedures and tables for inspection by attributes.
Key terms: ISO 6925:1982, textile floor coverings, burning behaviour, tablet test, methenamine tablet, ambient temperature, acceptance testing, quality control.
