What is the criteria for a material to be considered non-combustible?

The furnace and specimen temperature rise must not exceed 50°C, sustained flaming must not exceed 10 seconds, and the average mass loss must not exceed 50% of the original mass.

What size must the test specimen be?

The specimen must be cylindrical with a diameter of 45 (+0/-2) mm and a height of 50 ± 3 mm, with a volume of approximately 80 cubic centimeters.

What temperature is the testing furnace set to?

The furnace is stabilized at a steady temperature of 750 ± 5 °C before the specimen is inserted.

IS 3808

: 1979

Method of test for non-combustibility of building materials

CurrentSpecializedTesting MethodFire Safety · Fire Safety

Download PDF BIS Portal Google

IS 3808 specifies the testing procedure to determine whether a building material is classified as non-combustible. The method involves placing a prepared cylindrical specimen in a vertical tube furnace heated to 750°C and observing the temperature rise, duration of sustained flaming, and mass loss.

Method of test for non-combustibility of building materials

Quick Reference Values

furnace stabilization temperature750 ± 5 °C

specimen diameter45 +0/-2 mm

specimen height50 ± 3 mm

maximum permitted temperature rise50 °C

maximum sustained flaming duration10 seconds

maximum average mass loss50 %

Practical Notes

This test evaluates the bulk material; materials with combustible surface layers or thin facings may pass this test but still pose a fire hazard, thus requiring additional surface spread of flame tests (like IS 8736).

Specimens must be rigorously conditioned in a ventilated oven at 60°C for 20 to 24 hours and cooled in a desiccator prior to testing to ensure moisture vaporization does not skew temperature readings.