Intumescent Strips for Fire Doors

What are intumescent strips?

Fire doors are designed in such a way that it creates a barrier, compartmentalising a section or part of a premises, preventing smoke and fire from travelling though one part of the building and quickly onto another. When fire doors are installed correctly, small gaps can be seen between the door and frame which could impair the fire door’s ability to prevent the spread of fire and smoke. Intumescent strips, or intumescent seals, are heat activated seals that are placed on either the edge of the door or the frame to essentially fill these gaps for the event of a fire.

How intumescent strips work

Intumescent strips contain a heat reactive chemical that causes it to swell up when exposed to these conditions, typically in the event of a fire. Activating at around 200°C, the intumescent strips expand to many times its original size, in order for it to “seal” the gap around the door. This in turn, ensures that fire and smoke cannot lip itself around the door and occupy the escape route, making it difficult to escape.

Smoke seals, also known as cold smoke seals, have a distinctive feature of an additional brush that fits around the edges of the door and is usually combined with an intumescent strip. The brush is designed in such a way that even when the fire has not reached the intumescent seals activation temperature, the brush will reduce the amount of smoke that can lip itself around the door, keeping the escape route as clear as possible for as long as possible to not hinder evacuation.

Types of intumescent strips

Intumescent strips are often supplied in either rebated or surface mounted options. Rebated strips can often be found in brand new doors, as a channel is often routed out during manufacture to allow for the strip to be installed when it is being fitted. As the routing is done at the manufacturing stage of the door, it does not void its fire rating. Surface mounted intumescent strips are a solution to replace damaged strips on older fire doors or to be retrofitted on doors that did not originally have seals installed. Intumescent strips are only installed on the top and sides of fire doors, different seals can be fitted to the bottom of the door, should these be required.

Intumescent seals prevent the spread of fire but you may also need smoke seals, in addition to also prevent the spread of toxic smoke. Your fire door inspector, or fire risk assessor, will be able to advise you on which type or types of seals you require for your fire door needs.

Fire Only – Intumescent seals are for use where no smoke seals are required. These are likely to be used for doors that are for a small side room, such as a broom cupboard without a fire alarm, which in turn leads to a corridor with automatic fire detection. On this occasion, it is important that the door allows for the cold smoke to leak from the cupboard into the corridor so that the fire alarm is able to be activated and alert the occupants to the fire.

Fire and Smoke – Fire and smoke seals create a safe and effective barrier against fire, cold smoke, and hot gases produced in a fire. The smoke seal, in particular provides a permanent barrier to toxic smoke, which may impede an individuals’ ability to effectively escape via the emergency routes. This is particularly important as it is key to know that smoke fumes travel faster and further than the fire itself, causing more harm to an individual.