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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.
Frequently referenced clauses
Cl. 4Apparatus and Equipment
Cl. 5Test Specimens and Conditioning
Cl. 6Test Procedure
Cl. 7Criteria of Non-combustibility
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
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.