Ducts, dampers & transits · Transit concept

What is a cable-transit system?

Written by Scott Cunningham, Compliance Manager

Last reviewed 13 August 2026 Next review August 2027

ducts and dampers
transit concept

Short answer

A cable-transit system is a framed arrangement that lets cables pass through a fire-resisting element and be changed later without rebuilding the seal, within what the tested system permits.

What to do next

Send the tag, the schedule reference, the drawings you have and photographs of the actual condition. We will tell you what they show, what they cannot, and what else is needed before anyone gives a conclusion.

Service penetrations Request a quote

General information only. A conclusion about a specific condition requires the actual construction, the evidence behind it and the site condition to be reviewed.

Standards referred to

AS 4072.1—2005: Components for the protection of openings in fire-resistant separating elements — Service penetrations and control joints How a service passing through a fire-resisting wall or floor, and how a control joint in one, is required to be treated. Referenced by NCC 2022 Volume One C4D15, C4D16.
AS 1530.4—2014: Methods for fire tests on building materials, components and structures — Fire resistance tests for elements of construction The test standard. An FRL means nothing except as the result of a test to this standard, on a specimen, in a specific configuration.

Cited for context. The edition that applies to a project is the one the project documents call up.

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Can new cables be added to an existing cable transit?

Often, where the specific system, its capacity and the proposed service arrangement support the change. Adding cables beyond what the evidence covers turns a maintainable transit into an undocumented penetration.

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What is the difference between a fire damper and a smoke damper?

A fire damper is intended to restrict the spread of fire where a duct or opening passes through a fire-resisting barrier, and typically closes in response to heat. A smoke damper is intended to control the movement of smoke, and is generally operated by a detection or control system rather than by heat alone. Combination fire and smoke dampers perform both functions. Which one an opening requires depends on the building design, the system duty and the evidence supporting the installed assembly — and a damper being present in an opening does not tell you which requirement it was installed to meet.

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What is the difference between a tested system and a product?

A fire-stopping product is a material or component. A tested or assessed system is the complete configuration in which that product is supported to perform. Buying the right brand does not prove the installation matches the system evidence.

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