BS476 Part 6 Building Material Fire Tester Fire Propagation
Apparatus 1300-1450kg/M3
Building Material Fire Tester of BS 476 specifies a method of test, the result being expressed as
a fire propagation index, that provides a comparative measure of
the contribution to the growth of fire made by an essentially flat
material, composite or assembly. It is primarily intended for the
assessment of the performance of internal wall and ceiling linings.
The Building Material Fire Tester shall consist of a combustion chamber with a specimen holder
fixed to one face. The combustion chamber shall contain a
horizontal gas burner tube and two electrical heating elements and
shall be surmounted by a removable steel chimney and cowl.
Building Material Fire Tester Combustion chamber
The walls of the chamber shall be made from 12.5 mm thick asbestos
cement board2) having a dry density within the range 1 300 kg/m3 to
1 450 kg/m3. The internal dimensions of the chamber shall be 190 mm
× 190 mm × 90 mm.
An air inlet slot measuring 96 mm × 25 mm and a mica observation
window measuring 50 mm × 50 mm shall be provided together with a
hole for the discharge of combustion gases and a suitable fixing
for the chimney and cowl.
A steel baffle plate 200 mm × 40 mm shall be fixed horizontally to
the top of the combustion chamber above the window. Four steel rods
shall be fitted to the combustion chamber to enable the specimen
holder to be located and fixed firmly in position during each test.
After allowing any residual gas within the Building Material Fire Tester combustion chamber to disperse, simultaneously turn on the gas
supply and ignite the jets using the gas igniter; time the test
from the time of ignition. After 2 min 45 s, turn on the electrical
supply to give an indicated input of 1 800 W; at 5 min after the
time of ignition, reduce this indicated input to 1 500W.
