Manufactured fire doors are currently tested to British Standard 476: Part 22: 1987. This test determines the integrity and insulation of a doorset (i.e. the door and frame) when subjected to a furnace test. British Standard 476: Part 8: 1972 is superseded by this test.

1. Manufacturers Identification Scheme
A number of manufacturers set a plastic plug into the edge of their doors, indicating the potential fire resistance rating when tested in accordance with British Standard 476: Part 20/22: 1987.

An explanation of the symbols used is shown below:

2. Performance
A fire door is designed to function both as a door and as a barrier to a fully developed fire in a building. (Note: The term should really be 'fire resisting doorset' since leaf and frame act together in a fire resistance context.) Although any closed door will have some delaying effect on the development and spread of a fire, a fire door must be proven to be capable of resisting the effects of a standard fire test for stipulated periods, usually 20 or 30 minutes. The requirements for fire doors are quite complex; a fuller description is given in the Timber Research and Development Association (TRADA) Wood Information Sheet "Technology of fire resisting doorsets" (Section 1 Sheet 13 - 1992).

Fire resisting doors should generally be purpose-designed and manufactured door leaves and frames. When refurbishing or upgrading the structural fire protection of existing buildings, it is usually preferable to install new certificated doors which incorporate the latest technology and will perform consistently if involved in a fire.

3. Upgrading Existing Doors
There are limited occasions where it is either desirable or necessary to retain existing doors, but increase their sometimes minimal fire resistance to a useful and/or statutory level. These considerations apply most frequently in a building of historic merit where there is a need to maintain its character whilst improving fire protection. Upgrading might also be considered where the doorset is of very substantial construction and needs little modification to bring it up to the required level of performance.

Circumstances will vary from building to building and doorset to doorset. It is important therefore to look at each case individually when assessing the potential for upgrading. In view of the wide variety of types of door, it is not possible to state any one method of upgrading which would ensure an acceptable performance in all cases. Further guidance is available in the TRADA Wood Information Sheet "Fire Resisting Doors by Upgrading" (Section 1, Sheet 32 - 1998).

Normally, representative samples of an intended design of fire doorset are required to be tested (to BS 476: Part 22: 1987 "Methods for determination of the fire resistance of non-load bearing elements of construction"). Obviously this is rarely, if ever, feasible with doorsets of special merit which have been upgraded and, therefore, it will be necessary to provide an assessment of likely performance in lieu of a test result. Test laboratories which are accredited by UKAS (United Kingdom Accreditation Service) are widely recognised as being competent to issue such assessments.

There are few occasions when it is possible to achieve a satisfactory level of fire resistance by the application of an intumescent coating to the door. As with any other method of upgrading, the existing door must be of suitable quality and stability so as to ensure an acceptable performance. Where a propriety coating is used it must be applied by a competent person and strictly in accordance with the manufacturers instructions. Once applied, a certificate will be required from the contractor indicating adherence to the manufacturers guidance and instructions.

It is re-emphasised that upgrading will only be acceptable in exceptional circumstances and that the agreement and approval of the fire authority must be obtained before any upgrading work is commenced.

4. Glazing in Fire Resisting Doors
Any glazing within a door and any associated fanlights should be installed and fixed in accordance with the British Standards Institution Published Document PD 6512 "Use of Elements of Structural Fire Protection with particular reference to the recommendations given in British Standard 5588 Fire Precautions in the Design and Construction of Buildings": Part 3: 1987 "Guide to the Fire Performance of Glass".

Should it be decided to use an unwired fire resisting glass, the installation specification supplied by the manufacturer must be strictly complied with.

5. Door Furniture
Fire resisting doors are generally required to be fitted with positive check action self-closing devices. It is important to be aware that not all door closers are designated to operate under fire conditions. Under certain circumstances it may be permissible for doors to be held open on mechanical or electrical hold open devices connected to an automatic fire detection system.

Latches fitted to fire resisting doors should have a brass or steel tongue which engages into a brass or steel keep plate.

One and a half pairs of steel or brass hinges should be fitted, the hinges must have a melting point of not less than 800 degrees centigrade. Hinges should be fitted using 32mm number 8 screws of brass or steel.

Should it be necessary to fit a letter plate to a fire resisting door it will probably be necessary to fit a steel inner flap as well as the letter plate.

Detailed guidance on door furniture may be obtained from the Association of Builders Hardware Manufacturers Code of Practice "Hardware Essential to the Optimum Performance of Fire Resisting Timber Doorsets".