When cable trays pass through walls or floors, seal openings using fire-rated penetration sealing materials. Do not modify or damage the tray coating or structure during use. Where cables pass through shafts, walls, slabs, or enter electrical panels or cabinets, openings shall be tightly sealed with firestopping materials in accordance with. Is there an article that I might have missed that prohibits materials foreign to electrical system to pass through a cable tray? We are trying to propose a route for the cable ladder (horizontal) and the best route happens to be the location of vertical hanger rods that will support the ceiling. NEC section 300-8 does not permit any tube, pipe, or equal for water, air gas, drainage, steam, or any service other than electrical in raceways or cable trays containing. Fire-resistant cable trays are often specified in stairwells and escape corridors. Their role is to prevent tray deformation or collapse that could: Obstruct evacuation paths Expose live cables to occupants or firefighters This is a key consideration in buildings with long evacuation times. Fire. In particular, heat and smoke developments in corridors and stairwells that lead into the open air in emergencies are a major risk. Smoke poisoning is the cause of death of 95% of all victims of fire. To evacuate people safely from the building in case of fire, escape and rescue routes, as the. A.