Technical library
Ducts, dampers & transits
Fire-resisting duct systems, dampers and cable transit systems.
Ducts, dampers & transits articles
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.
Scott CunninghamWhat is a cable-transit system?
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.
Scott CunninghamWhat 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.
Scott CunninghamWhat 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.
Scott CunninghamWhat makes a fire-resisting duct system different from ordinary ductwork?
A fire-resisting duct system is a tested or assessed construction in which duct, protection, joints, supports, access and penetrations work together. Adding insulation to ordinary ductwork does not create that system.
Scott CunninghamWhat should be checked around a fire damper installation?
The damper, the opening, the installation method, the connection or breakaway detail, access provision, orientation, and — where applicable — the control and commissioning arrangement. A label on the damper says nothing about the installation around it.
Scott Cunningham
Still not sure what you are looking at?
Send the tag, the schedule reference and photographs of the actual condition. We will tell you what they show and what else is needed.