What is a Class 1 material according to IS 12777?

A material with a Flame Spread Index (Is) of 25 or less, indicating very low surface flame spread characteristics.

What is the primary output of the test described in this code?

The primary output is the Flame Spread Index (Is), a dimensionless number which is then used to classify the material into one of four classes (Table 1).

Where is this classification primarily used?

It is primarily used for selecting materials for wall and ceiling linings, finishes, and other interior components in buildings, as stipulated by the National Building Code (NBC), to manage fire spread.

Does this test measure fire resistance?

No, this test measures surface flame spread, not fire resistance. Fire resistance (measured in hours) is the ability of a structural element to withstand fire and is determined by tests like IS 3809.

IS 12777

: 1989

Method for Classification of Flame Spread of Products

CurrentFrequently UsedTesting MethodBIMFire Safety · Fire Safety

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This standard specifies the test method and classification system for the surface flame spread of products using a radiant panel apparatus. It categorizes materials into four classes based on a calculated Flame Spread Index, which helps in selecting suitable materials for building interiors to control fire propagation.

Method for Classification of Flame Spread of Products

Quick Reference Values

Flame Spread Index (Is) for Class 1< 25

Flame Spread Index (Is) for Class 226 to 75

Flame Spread Index (Is) for Class 376 to 200

Flame Spread Index (Is) for Class 4> 200

Standard test specimen size150 mm x 460 mm

Radiant panel temperatureApprox. 670°C at the upper edge

Key Formulas

Is = Fs * Q — Flame Spread Index

Fs = 1 + (1 / (t3-t0)) + (1 / (t6-t3)) + (1 / (t9-t6)) + (1 / (t12-t9)) + (1 / (t15-t12)) — Flame Spread Factor

Q = C * T — Heat Evolution Factor

Practical Notes

This test is commonly known as the 'Radiant Panel Test' for surface flammability.

The classification (Class 1 to 4) is a critical input for architects and fire engineers to comply with material requirements in the National Building Code of India (Part 4: Fire and Life Safety).

The test methodology is technically similar to the international standard ASTM E 162.