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Firewalls can pass through cable trays

Optical access and telecom site reference Published 20 May 2025

Use this reference to prepare product questions for CGWEB NETWORKS. Check interfaces, capacity, protection and installation requirements against the current product documentation.

Cable trays can pass through firewalls if the openings are properly firestopped to maintain the wall's fire-resistance rating.

Firestopping Requirements

When a cable tray passes through a fire-rated wall, the opening must be sealed with approved firestop materials to preserve the firewall's integrity and rating. This includes: Firestop caulks or mastics: Intumescent or latex-based sealants that expand under heat to block fire and smoke. Firestop packs or mineral wool: Used for larger openings to fill gaps around cables and trays.

Backing plates or fire-rated boards: Installed for structural support and to maintain fire resistance in large penetrations. All gaps around the tray, including the top, bottom, and sides, must be tightly sealed without voids, and the firestop system should be UL-listed or tested for the specific wall and tray configuration.

Installation Considerations

Tray type and size: Ladder, solid-bottom, or other tray types may require different firestop methods. Openings should be slightly larger than the tray to allow proper sealing. Sequence of installation: Firestopping is typically done after cable routing but before final wall finishes, ensuring accessibility and proper sealing.

Maintenance and retrofitting: Any alterations to the tray or wall require reinstating the firestop with the same type of materials to maintain fire integrity. Compliance and StandardsNEC 300. 21: Requires firestopping for cable penetrations through fire-rated walls.

UL-listed systems: Products like 3M Fire Barrier Moldable Putty+, FS-ONE MAX, or other intumescent caulks are commonly used to meet fire ratings of 1–3 hours depending on wall construction. Inspection: Firestop installations should be inspected to ensure no cracks, voids, or gaps remain, and that the system conforms to the tested configuration.

Summary

Cable trays can pass through firewalls, but the openings must be properly firestopped using approved materials and methods to maintain the wall's fire-resistance rating. This ensures compliance with safety codes, prevents fire and smoke spread, and allows safe operation of electrical systems.

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Firewalls can pass through cable trays

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