If any cable listed by UL has been tested and verified to meet a fire rating, then the UL icon, fire rating and approval number can be printed on the cable.

1. Plenum Flame Test / Steiner Tunnel Test (CMP stage)

This is the most demanding Cable (Plenum Cable) in the UL fire protection standard. The safety standard is UL910. The test requires multiple samples to be laid on the horizontal air duct of the device and burned for 20 minutes with an 87.9KW gas Bunsen-burner (300,000 BTU/Hr). Eligibility criteria were that the flame should not extend more than 5 feet from the front end of the gas Bunsen burner flame. The maximum peak value of the optical density was 0.5 and the maximum average density value was 0.15. This CMP cable is usually installed in the air reflux booster system used in ventilation ducts or air handling equipment and is approved for use in Canada and the United States. The flame retardant performance of FEP/PLENUM materials conforming to UL910 standard is better than that of low-smoke halogen-free materials conforming to IEC60332-1 and IEC60332-3 standard, and the concentration of smoke when burning is low.

2. Trunk - CMR (Vertical Flame Test / Riser Flame Test)

This is UL standard commercial grade Cable (Riser Cable), applicable to the safety standard of UL1666. The experiment specified that multiple samples were laid on the simulated vertical axis and used with the specified 154.5KW gas Bunsen burner (527,500 BTU/Hr) for 30 minutes. Eligibility criteria were that flames should not spread to the upper part of a room 12 feet high. There is no smoke concentration specification for trunk-grade cables, which are generally used for floor vertical and horizontal wiring.

3. Commercial Grade - CM grade (Vertial Tray Flame Test)

This is UL standard commercial grade Cable (General Purpose Cable), applicable to the safety standard UL1581. For the experiment, multiple specimens were laid on a vertical 8 ft high bracket and burned with a prescribed 20KW ribbon blowtorch (70,000BTU/Hr) for 20 minutes. The eligibility criterion is that the flame should not spread to the upper end of the cable and extinguire itself. UL1581 and IEC60332-3C are similar, but the number of cables is different. Commercial grade cables do not have smoke concentration specifications and are generally only used Horizontal routing on the same floor should not be applied to vertical wiring on the floor.

4. General Class -CMG class (Vertial Tray Flame Test)

This is a General Purpose Cable in UL standard, applicable to the safety standard UL1581. Commercial grade and general grade test conditions are similar, both for Canada and the United States approved use. General grade cable has no smoke concentration specification, generally only applied to the horizontal wiring of the same floor, not applied to the vertical wiring of the floor.

5. Home Grade - CMX level (Vertial Wire Flame Test)

This is the UL standard home class Cable (Restricted Cable), applicable safety standards for UL1581, VW-1. The experiment stipulated that the sample was kept vertical, burned (30,000 TU/Hr) with the blowtorch used for the test for 15 seconds, then stopped for 15 seconds, and repeated 5 times. The eligibility criteria are that the residual flame should not exceed 60 seconds, the specimen should not burn more than 25%, and the surgical cotton pad on the bottom should not be ignited by falling objects. UL1581-VW-1 is similar to IEC60332-1 except that the time of combustion is different. This grade also has no smoke or toxicity specifications and is only used in single-cable home or small office systems. Such cables should not be used in bundles and must be bushed.