Duct Protection & Dampers
Duct wrap, board enclosure and dampers — the whole opening, not the visible product.
Overview
A duct crossing a fire-resisting element is not one item. It is the duct, the protection on it, the supports, the joints, the access doors, the opening in the wall and, where there is one, the damper sitting in it. Any of those can be the reason the system does not hold. FRS builds and records all of them.
Duct wrap and board enclosure
A fire-resisting duct system is more than insulation wrapped around sheet metal. The duct construction, the protection system, orientation, supports, joints, access doors, penetrations and the tested or assessed arrangement all matter. Adding insulation to ordinary ductwork does not create that system.
It also matters which way the fire is expected to come. A duct tested for fire outside the duct is not evidence for a duct where the fire can start inside it — kitchen exhaust and smoke spill ducts are the usual cases — and the two are protected differently. Swapping one for the other because the FRL number matches is a mistake that generally surfaces at handover, when the certification does not.
Wrap or board is not a preference. Duct duty, geometry, the space available, the supports, access requirements, the surrounding construction and which arrangements the evidence covers decide it between them.
Fire dampers
A fire damper closes an opening where a duct passes through a fire-resisting building element, and closes on heat — usually through a thermal release device such as a fusible link. That link is the part to look for on site, and the part most often painted over, tied back, or replaced with the wrong temperature rating.
Most damper defects are not in the damper. They are in the construction immediately around it: whether the damper sits in the plane of the element or within the offset its evidence allows, whether the retaining angles are the ones specified and fixed the way the evidence requires, whether the gap between sleeve and opening is fire-stopped to a supported detail, whether the duct-to-damper connection is a breakaway connection where one is required, whether there is an access panel big enough and close enough to inspect and reset the damper, and orientation — a damper tested vertically is not evidence for a horizontal installation.
A label on the damper says nothing about any of that.
Smoke dampers
A smoke damper does a different job. It controls the movement of smoke and is generally driven by the detection or control system rather than by heat alone, because smoke moves well before the temperature at the damper rises. Where a damper has a smoke-control duty it sits inside the system requirements for that installation and has to be commissioned as part of it.
A damper being present in an opening does not tell you which requirement it was installed to meet. That is settled by the project documents and the commissioning record, not by looking at it.
What FRS can take on
- Duct wrap — fire-resisting duct protection installed to the tested or assessed arrangement, including supports, joints and access provisions.
- Board enclosure to ducts — rigid board systems where the duct duty, geometry or access makes boarding the supported answer.
- Fire dampers — installation at the fire-rated boundary, with the opening, retaining angles, breakaway connection and access panel built to the supported system.
- Smoke dampers — installation of the damper and the fire-rated boundary around it, coordinated with whoever holds the control and commissioning scope.
- Rectification — existing duct protection and damper installations, identified and brought back to a system that stands up.
- Inspection and recording — condition, location, system and evidence captured against each item.
- A written scope line — we set out in writing which parts of the damper installation are ours and which sit with the mechanical or commissioning contractor, so it is agreed before site rather than discovered at handover.
Technical library
Duct, damper and transit guides.
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 CunninghamQuestions
Frequently asked questions
- Is duct wrap the same as a fire-rated duct?
- Not automatically. A wrap is one component of a tested or assessed duct protection system. The duct, supports, joints, access and installation details matter as well.
- Does every duct through a fire wall need a fire damper?
- Not necessarily — it depends on the building design, the duct function and what the project documentation calls for. Send us the mechanical and fire drawings and we will tell you what is actually required.
- Who commissions the damper?
- That has to be clear in the project scope before anyone is on site. We install and record the damper and the fire-rated boundary around it; actuation, control wiring and commissioning stay with the mechanical, electrical or commissioning contractor. We will say so in writing rather than leaving it to be discovered at handover.
Drawings, photos or a defect report in front of you?
Send what you already have. We will tell you what else is needed before the work can be reviewed, priced or booked for site inspection.