BESA said it was acting after annual inspections carried out by maintenance contractors found that “a huge number of dampers” had been incorrectly installed.

Head of technical Graeme Fox said that many did not comply with manufacturers’ instructions and needed remedial action “without delay”.

Fox said: “We have been alerted to the very dangerous practice of using self-drilling ‘tek’ screws which do not melt when temperatures rise during a building fire.

“This means spring-loaded dampers will not be released to contain the spread of fire within the zone and ensure the integrity of the fire stopping measure.

“Dampers must be secured by fusible fixings that allow the duct to break away otherwise the collapsing duct could pull the damper out of place and break the seal between the fire zones.

“While this is clearly a very worrying situation, we can take some reassurance from the fact that this problem is being brought to our attention by the increasing frequency of fire damper inspections and tests as awareness grows of this extremely important issue.

“We would urge contractors to alert their clients immediately so all the necessary checks and repairs can be carried out.”

An interim technical bulletin covering the issue is available to download free online here.