Install fire barriers within the tray to isolate different fire zones. Only use fireproof trays for flame containment or isolation, not for unrelated. Cable tray systems help organize and support electrical cables efficiently, but improper installation or maintenance can increase the risk of electrical fires. Understanding proper cable tray fire safety practices is essential for protecting buildings, equipment, and occupants. Commercial buildings. The following charts give the number of 3M pillows needed to completely firestop an opening that cable tray passes through. Where cables pass through shafts, walls, slabs, or enter electrical panels or cabinets, openings shall be tightly sealed. Question 1: Can mechanical utility piping or tubing containing water or compressed air be installed in cable trays with electrical cables? Answer: No. UL Listed Systems Concrete Wall - C-AJ-4056 3 HR F-Rating, 3/4 HR T-Rating Gypsum.