Designed to match the rigors of the application, this test is quite demanding. About 20 years ago, UL first used this apparatus to test plenum cable. This work became the basis for UL's development of UL 910. In the UL-910 test, a single layer of 24 foot lengths of cable are supported by a one foot wide cable rack, which is filled with cables. During the 20 minute test, flame spread is observed through small windows spaced one foot apart.
Smoke is measured by a photocell installed in the exhaust duct.
Riser A riser is a vertical pathway or space between floors. Cables within risers must be rated in order to prevent the spread of fire between floors. This test is not a stringent as the UL 910 test. Riser rated cables can be used in general purpose applications in place of cables with lower ratings. This test chamber is an eight by four simulated shaft, twelve feet high between the source of ignition and the floor above.