The LWF Blog

Passive fire protection for Building Professionals – Part 14

April 23, 2020 9:21 am

In LWFs blog series on passive fire protection for building professionals and contractors and those with an interest in structural fire protection issues, we aim to give an overview of the important role passive protection plays in the overall fire safety provision of a building. In part 13, LWF looked the components used in fire doors, including letterboxes, intumescent strips and smoke seals. In part 14, we continue to discuss how the correct choice of components is essential for a correctly-functioning fire door.

Current industry standards indicate that the intumescent strip used on a 30-minute fire door should be 15 mm in width. In the past, 10 mm was considered acceptable, but the increased width helps ensure the integrity of the fire door for the full duration of fire resistance. A 60-minute fire door should be fitted with 20 mm, which can be either one 20 mm combination intumescent and cold smoke seal strip, or two 10 mm strips installed separately.

Intumescent seals and cold smoke seals of different brands can expand at different temperatures. For this reason, it is important to install the same intumescent strip and cold smoke seal as has been originally tested with the door. Where this is not possible, consistency of performance is paramount and the intumescent seal and cold smoke seal used should be installed as one continuous length, avoiding the issues caused by a mixture of different brands being used.

Perhaps the most important component of a fire door that should be considered is the self-closing device. Older fire doors may have used sprung hinges, rising butt hinges, single chain internal self-closers or sprung arm closers, but these are now considered insufficient and newer, safer options are available.

The self-closing mechanism chosen for the fire door should be a substantial device that confirms to BS EN 1154 ( The device should be a minimum power size three and this should increase with larger and heavier doors. If the closer does not meet this standard than specialist advice should be sought.

In part 15 of this series, LWF will start to discuss passive fire protection provided by walls and ceilings. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact LWF on freephone 0800 410 1130.

Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 25 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.

While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.


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