Dampers

Frequently asked questions

What types of damper are there?

Four common types. Fire dampers close to stop fire and smoke crossing a compartment line. Intumescent fire blocks are passive cartridges that expand and seal an air transfer opening when heated. Volume control dampers set and balance airflow in a branch. Back draught or non-return dampers let air out but close against reverse flow. A single combination unit can provide both fire protection and volume control.

How do I choose the right damper?

Start with the job. If a duct or grille passes through a fire-rated wall or floor you need a fire damper or intumescent fire block matched to the rating of that element. If you are balancing flow between branches you need a volume control damper. If you are stopping cold air, smells or noise returning through an outlet you need a back draught damper. Match the size to the duct diameter, and call us if a single run needs more than one type.

Do all dampers provide fire protection?

No, and this is the most important distinction on the page. Only fire dampers and intumescent fire blocks are rated to hold back fire and smoke, and they carry a classification stating how long they last. Volume control and back draught dampers manage airflow only and have no fire rating whatsoever, so they must never be used in place of a fire damper where the Building Regulations require one, however similar they look once installed.

What does an EI rating mean?

EI is the European fire classification used for fire dampers. E stands for integrity, meaning the damper stops flame and hot gases passing through. I stands for insulation, meaning it also limits heat transfer to the unexposed side. The number is the performance in minutes, so EI 120 means both criteria are met for 120 minutes. The damper rating should match the fire resistance of the wall or floor it penetrates, which is why the drawings matter more than the duct size when specifying.

How does a fire damper close?

Two common mechanisms. A mechanical fire damper is held open by a thermal release, usually a fusible link that melts at a set temperature and lets a spring-loaded curtain or blade drop shut. A motorised fire damper is held open by an actuator and driven closed on a signal, typically from the fire alarm or a smoke detector, which allows remote testing and monitoring. Check which type the specification calls for, since a mechanical damper responds only to heat at the damper itself, not to smoke detected elsewhere in the building.

Do fire dampers need access for inspection?

Yes. Fire dampers are life safety devices and require periodic inspection and testing, so every damper needs an access panel large enough to reach the mechanism and reset it. This is routinely overlooked at first fix and then very expensive to correct once ceilings are closed. Plan access panel positions at the same time as the damper positions, and keep a record of where each damper is, because an undocumented damper does not get tested.

Where should a volume control damper be fitted?

In the branch it is controlling, far enough from the terminal that the turbulence it creates has settled before the air reaches the grille, and somewhere a person can actually reach to adjust it. A damper throttled down hard is a sign the branch is oversized rather than a solution in itself, and it will generate noise at the blade. Leave it accessible, because the system will need rebalancing after any change.

What does a back draught damper do?

It lets air pass in one direction and closes against flow in the other, using either gravity-hung blades or a light spring. It stops cold air, smells and noise coming back through an extract outlet when the fan is off, and on shared or multi-outlet systems it stops one extract point discharging into another. On any run that terminates externally without a self-closing grille, it is what keeps wind from pushing straight back down the duct.

Do you supply dampers for trade and project work?

Yes. We supply M&E contractors, installers, developers and facilities teams, and hold stock from 100mm to 600mm for next day delivery. Send the drawings, the fire strategy or a damper schedule and we will price it, confirm ratings against the compartment lines, and flag anywhere access looks like it has not been allowed for. Call 0161 399 3825 or email hello@efans.co.uk.