Cable trays should not pass through a fire rated wall because the metal tray can conduct heat through the wall and may ignite materials on the other side. Cable Trays have been permitted in the hazardous (classified) locations in the National Electrical Code for Class I (flammable vapor and gases) since the 1978 NEC and have been used extensively in chemical plants, refineries, and other types of facilities. Where cables pass through shafts, walls, slabs, or enter electrical panels or cabinets, openings shall be tightly sealed with firestopping materials in accordance with. Cable trays may be designed to cross through partitions and walls, as well as go vertically through platforms and floors. 2 should be provided in accordance with NEC Section 300. Chemical plants have risks like explosive gases, dusts, or vapors. The penetration of fire rated walls and floors is often necessary to accommodate electricity, data cables and piping.