Doors & Alarms

[Gary Wicks]

I have a question regarding Fire Doors and Smoke Detection.

When to fit smoke seals to a fire door and when to fit an additional smoke detector? As we know smoke alarms are activated when they detect smoke, but what happens if that flow of smoke is prevented by a fire door with cold smoke seals? As an example there are a number of fire alarm designs that have smoke detection in the escape routes, some rooms immediately off the escape route may have detection and some may not, but the rooms could all be fitted with fire doors.

If a fire breaks out in a room with no detection the door to the escape rout could prevent the travel of smoke to the nearest detector which could delay the detection of the fire, which could result in the loss of both life and property! Should we therefore only fit intumescent seals to these doors???

 

[AnthonyB]

Smoke seals must be fitted to fire doors protecting escape routes. Smoke seals are important to enable occupiers to escape down the protected route without being subjected to smoke which can be toxic, impede breathing and affect vision. Cool smoke, often given off by smouldering furnishings and electrical equipment, is exceptionally toxic and tends not to rise and thus will not operate smoke detectors on escape routes, therefore smoke seals on fire doors are essential.

This phenomenon, plus the fire gases passing through the cracks around doors (back when doors fire doors just had rebates or early intumescent seals with no smoke brushes) can produce smoke sufficiently dense and cool for a corridor to become smokelogged before adequate warning can be given by detectors in the corridor itself  - this is why in the 1980's guidance on the provision of detection for hotels was updated to require detectors in rooms and Categories of system were born with L3 being the minimum detection category (rooms opening onto escape route and the escape route).

So with no smoke control to the doors you risk the escape route becoming untenable (or logged enough to put users off going through it) without a single detector activating. With smoke brushes you hold back most by products with the first leakage being hot smoke at the upper edge that will trigger a corridor head before the door fails.