A fire damper that closes may still fail

Routine inspection and testing provide important evidence that a fire damper can operate. However, seeing a damper close does not demonstrate that the complete installation will maintain compartmentation throughout a fire.

A CROSS-UK report on self-drilling screws in fire-damper installations examines this important distinction. Surveys have identified dampers connected to ductwork using self-drilling screws rather than the low-melting-point fixings needed to form an effective breakaway connection.

The presence of these fixings has sometimes resulted in installations being recorded as failures and extensive remedial work being recommended. Questions have then arisen about whether this response is proportionate where the screws do not obstruct the damper and the mechanism appears to operate correctly.

The answer requires us to look beyond initial operation.

The damper is part of a system

A fire damper is intended to preserve the fire separation where ductwork passes through a fire-resisting element. Its performance depends not only on the damper closing, but also on its supporting construction, penetration seal and connection to the adjoining ductwork.

During a developed fire, ductwork may soften, distort or collapse. A correctly formed breakaway connection allows the failing ductwork to separate without transferring damaging forces to the damper. If non-fusible screws rigidly connect the two, the ductwork could distort the damper or pull it away from the supporting construction.

The damper may therefore close successfully during a routine test and still be unable to maintain integrity for the required period under fire conditions.

This illustrates a wider fire engineering principle. Testing one function of a component does not necessarily verify the performance of the complete fire safety system. The relevant question is not simply, “Does it operate?” It is, “Will the installation continue to fulfil its intended role under the conditions for which it is required?”

Compliance and proportionality

Recognising a credible failure mechanism does not mean that every legacy installation should receive an identical recommendation. The configuration of the damper, ductwork supports, accessibility, compartment function and consequences of failure may vary considerably.

Surveyors should therefore explain what has been observed, how it differs from the intended installation and why that difference matters. A recommendation based only on the presence of a particular fixing gives the dutyholder little assistance in understanding the risk or prioritising remedial work.

The Building Engineering Services Association’s TB59 reinforces the requirement for breakaway joints using appropriate low-melting-point fixings. For legacy installations, it also recognises that physical constraints may sometimes make replacement difficult. In those circumstances, a risk assessment should determine the appropriate action, necessary control measures and residual risk.

That is not permission to disregard non-compliance simply because a damper closes. It is a framework for reaching a proportionate and evidence-based decision.

Define the required outcome

This issue also demonstrates why fire strategies should define performance objectives clearly. If the strategy merely marks the position of a fire damper, it does not tell designers, installers or building managers what that damper must achieve.

The intended outcome is continuity of compartmentation for the required fire-resistance period. Installation, inspection, testing and maintenance should all be directed towards that outcome.

Fire safety assurance must examine complete systems and credible failure mechanisms. A successful functional test provides useful evidence, but it is not the same as evidence of performance in fire.

Pyrology Insight provides commentary on contemporary fire safety topics. It is intended to stimulate professional discussion and should not be relied upon as project-specific advice.