Even with the correct components, a fire door could be useless unless installed correctly. The installation instructions are specifically written for each door design, and must be followed to maintain the door's certification. They outline the permitted gaps between door and frame, what size and material the frame should be made from, how to attach the frame to the wall and the components required, and any trimming allowance for the door.

Installation is the final stage of the certification process. It is more than just hanging a door; it is a specialist task. If the door is wrongly installed, smoke and hot gases can easily travel through the gaps, and it may only provide a fraction of its expected resistance. If you are going to install fire doors, ensure you follow the instructions carefully, or better still, have the correct training and certification through FIRAS, the installer certification Scheme run by Warrington Certifire Ltd.