NBS Smoke Chamber

Smoke emission is regarded as a major hazard in fire situations, since it hinders escape of occupants and entry of fire fighters. Numerous methods have been devised for quantifying smoke generation from burning materials, but the most widely used laboratory-scale technique is the National Bureau of Standards (NBS) Smoke Box. Test specimens are burned in either the flaming or non-flaming (smouldering) mode, and the resulting smoke accumulates in a closed chamber system.

Optical density of the smoke is measured photometrically and data are presented graphically as cumulative optical density versus time curves, and maximum values are quoted either as measured or as normalised values accounting for specimen mass loss during the test. Although specimens are usually mounted vertically and the incident radiant heat flux is usually set at 25 kW/m2, options exist for testing specimens mounted horizontally (an advantage for testing certain thermoplastic materials which drip away from the flame in the vertical assembly), and at heat fluxes in the range 10 – 50 kW/m2 using a variable irradiance conical heater unit.

NBS Smoke Box tests can be conducted in accordance with national and international standards including BS 6401, ASTM E662, ISO 5659-2, and the maritime standard NES 711.

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