Overview
ISO 9151:2016 - "Protective clothing against heat and flame - Determination of heat transmission on exposure to flame" specifies a laboratory method to measure heat transmission through materials and assemblies used in protective clothing. The standard defines a repeatable test using a flame source and a small copper disc calorimeter to determine a Heat Transfer Index (HTI). Materials are ranked by HTI to indicate relative heat transmission under standardized conditions. ISO 9151:2016 explicitly notes that HTI is an index for comparison and should not be interpreted as a direct measure of real-world protection time.
Key topics and technical requirements
- Test principle: A horizontally mounted specimen is exposed to a flame (Meker burner) producing an incident heat flux of (80 ± 2) kW/m². Heat passing through the specimen is measured by a copper disc calorimeter; the time to reach a temperature rise of (24 ± 0.2) °C defines the HTI.
- Heat Transfer Index (HTI): HTI (flame) is the mean time, in whole seconds, for the calorimeter temperature rise, calculated from three specimens.
- Apparatus and materials:
- Meker gas burner with propane (commercial grade, ≥95% purity) or reported alternative gases.
- Copper disc calorimeter: 40 mm diameter, 1.6 mm thickness, mass (18 ± 0.05) g, thermocouples equivalent to Type T (36 gauge).
- Mounting block, specimen support frame, calorimeter location plate, recorder and template.
- Specimen preparation & environment: Specimens are tested without an air gap; conditioning and testing atmospheres are specified for temperature and relative humidity to ensure reproducibility.
- Calibration, tolerances & reporting: Procedures for calorimeter calibration, thermocouple stabilization, dimensional tolerances, and a defined test report form (Annex C) are included.
Applications and who uses it
ISO 9151:2016 is used for:
- Manufacturers of protective clothing and fabric suppliers assessing material performance against flame exposure.
- Accredited testing laboratories performing standardized thermal testing (PPE compliance, product development).
- PPE designers and safety engineers comparing fabric systems and layer assemblies.
- Procurement teams and regulators evaluating material suitability for heat-and-flame risk environments.
Practical uses include material selection, product grading, comparative performance testing, and supporting compliance documentation for industrial, firefighting, and oil/gas protective garments.
Related standards
- ISO 5725-2 - accuracy, repeatability and reproducibility for measurement methods.
- IEC 60584-1 and IEC 60584-3 - thermocouple reference tables and cable tolerances.
- See Annex A (significance), Annex B (material availability) and Annex C (example test report) in ISO 9151:2016 for additional guidance.
Keywords: ISO 9151:2016, protective clothing testing, heat transfer index, HTI, copper disc calorimeter, Meker burner, thermal protective performance, flame exposure testing.
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