Do cable trays have to be sealed off

Yes, cable trays can be sealed, particularly at penetrations through walls, floors, or fire-rated compartments, using firestopping, waterproofing, or gas-tight sealing systems.Firestopping and Safety ConsiderationsCable trays themselves are typically open structures designed for accessibility and ventilation, but when they pass through fire-rated walls, floors, or shafts, sealing is required to prevent fire and smoke spread. Openings around cable trays must be tightly sealed with approved firestopping materials such as fire-rated boards, firestop packs, firestop mastic, or fire-resistant mineral wool . Gaps inside and around metal trays should be sealed both internally and externally, ensuring no visible cracks or voids . For large openings, a fire-resistant backing plate may be installed before sealing .Sealing Methods and MaterialsSeveral systems are available for sealing cable trays:Intumescent coatings: Applied to the tray where it passes through fire-rated walls to expand under heat and maintain fire resistance .Modular firestop systems: Such as FIRSTO firestops, which are assembled around the cable run to seal penetrations in walls or floors .Self-compression plugs and sealants: Systems like SLIPSIL or RISE® provide fire-safe, gas, and watertight sealing for single or multiple cables .Covers and lids: For overhead or exposed trays, covers can protect against debris, liquids, or hot particles while maintaining accessibility .Installation and ComplianceSealing should be performed by trained personnel using approved materials, and the sealed penetration should be labeled with the fire resistance rating, date, and installer information . Cable trays should remain accessible for maintenance, and permanent enclosure of trays is generally discouraged unless required for fire or environmental protection . Metallic trays may require bonding and grounding continuity when sealed, depending on electrical code requirements .SummaryWhile cable trays are designed to remain open for ventilation and accessibility, they can and should be sealed at penetrations or in fire-rated areas using appropriate firestopping or sealing systems. Proper sealing ensures compliance with safety codes, prevents fire and smoke spread, and can provide environmental protection against water or gas ingress. Selecting the correct sealing method depends on the tray type, location, and applicable fire or building codes .