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IS 3808:1979 is the Indian Standard (BIS) for method of test for non-combustibility of building materials. 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
! 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.
building materialsinsulationcladdingfinishescomposite materials
International Equivalents
Similar International Standards
ISO 1182:2020International Organization for Standardization (ISO), International
HighCurrent
Reaction to fire tests for products — Non-combustibility test
Defines the primary international test method for determining non-combustibility using a vertical tube furnace.
BS EN ISO 1182:2020British Standards Institution (BSI), United Kingdom
HighCurrent
Reaction to fire tests for products - Non-combustibility test
The UK's adoption of the ISO 1182 standard, making it functionally identical.
ASTM E136-22ASTM International, USA
MediumCurrent
Standard Test Method for Assessing Combustibility of Materials Using a Vertical Tube Furnace at 750°C
A widely used US standard with a similar test principle but different pass/fail criteria and apparatus details.
BS 476-4:1970British Standards Institution (BSI), United Kingdom
HighWithdrawn
Fire tests on building materials and structures. Non-combustibility test for materials
The historical British standard upon which IS 3808:1979 was directly based.
Key Differences
≠IS 3808 uses simpler pass/fail criteria based on temperature rise (<50°C) and flaming duration (<10s), while modern standards like ISO 1182 have more complex criteria including mass loss (≤50%) as a mandatory classification parameter.
≠The test duration in IS 3808 is typically 20 minutes, whereas ISO 1182 specifies a 30-minute test duration, or until thermal equilibrium is reached.
≠Modern standards (ISO 1182, ASTM E136) require continuous digital data acquisition and have stricter furnace temperature stabilization protocols (e.g., drift <2°C over 10 min) compared to the less stringent requirements in the 1979 Indian standard.
≠IS 3808 does not specify mass loss as a performance criterion, although it is recorded. In ISO 1182, a mass loss of more than 50% automatically classifies the material as combustible.
Key Similarities
≈The fundamental test principle is identical: a small cylindrical specimen is inserted into a pre-heated vertical tube furnace to assess its thermal and flaming response.
≈All standards use a nominal furnace operating temperature of 750°C to simulate well-developed fire conditions.
≈The specimen geometry is very similar across the standards, typically a cylinder with a diameter of approximately 45 mm and a height of 50 mm.
≈All methods require the observation and timing of any sustained flaming from the specimen as a critical performance criterion.
Parameter Comparison
Parameter
IS Value
International
Source
Furnace Operating Temperature
750 ± 10 °C
750 ± 5 °C
ISO 1182:2020
Specimen Dimensions (Dia. x Ht.)
44 mm x 50 mm
45 mm x 50 mm
ISO 1182:2020
Criterion: Max Temp Rise (Furnace/Specimen)
≤ 50 °C
≤ 30 °C (average over final period)
ISO 1182:2020
Criterion: Sustained Flaming Duration
Not defined, but flaming for >10s is a failure
0 seconds
ISO 1182:2020
Criterion: Mass Loss
Not used for classification
≤ 50%
ISO 1182:2020
Standard Test Duration
20 minutes
30 minutes
ISO 1182:2020
Number of Specimens Tested
3
5
ISO 1182:2020
⚠ Verify details from original standards before use
Key Values6
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 %
Tables & Referenced Sections
Key Tables
No tables data
Key Clauses
Clause 4 - Apparatus and Equipment
Clause 5 - Test Specimens and Conditioning
Clause 6 - Test Procedure
Clause 7 - Criteria of Non-combustibility
Frequently Asked Questions3
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.