Standard Methods of Fire Testing for Light Diffusers & Lenses

Flammability Testing

• Light diffusers and lenses can become loose and fall out of their mounts when exposed to fire. Testing of light diffusers is performed according to Underwriters Laboratories of Canada (ULC) standard S102.3. Tests are run in a tunnel built according to standard ULC-S102. The test tunnel also meets American Society for Testing and Materials (ASTM) standard E84. According to "Plastics Flammability Handbook" by Jürgen Troitzsch, "an additional test for non-melting building materials, ULC-S127, is used if other tests give ambiguous results." ULC-S127 testing exposes three specimens to a maximum of fifteen minutes to an electric furnace heated to 750 degrees Celsius. The lenses or diffusers pass this test if they do not burn within thirty seconds of the start of the test and do not lose more than twenty percent of their weight.

Light Extinction Test

• During a fire, soot can obscure emergency lights. Light extinction is the measure of how badly light from a lens or diffuser is extinguished by particles in the air. The book "Flammability Testing of Materials Used in Construction, Transport and Mining" states "the light source, typically a gas-filled tungsten filament bulb with a color temperature of approximately 2900 K, and a collimating lens are mounted on one side of the duct." A second lens is paired with a light detector designed to mimic the human eye. The light received by the detector that is equivalent to the human eye is tested at different particulate levels.

Materials Testing

• Lighting is useless if the light melts during a fire. Thermoplastics are plastics that begin to soften below 200 degrees Celsius. Thermoplastic heat resistance is measured according to British Standard (BS) 2782: Part 1: Method 120A. Non-combustibility of other components in light diffusers must be tested. BS standard 476 Part 11 can be used as well as ISO EN 1182. Three samples of the components are placed in a specimen basket. After exposure to 750° Celsius for twenty minutes, if none of the samples rose by more than 50°C or burned continuously for more than ten seconds, they are classified as non-combustible.

Functional Testing

• Periodic testing ensures emergency lights will work when there is a fire. The frequency of testing depends on local laws. Emergency lights are required to have a backup power source to run at least ninety minutes after power is lost. Primary power is disconnected from the emergency lighting during tests. Emergency lights like illuminated exit signs and light diffusers are visually checked ninety minutes later to verify they are still operational.