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How safe are fire doors?

technical

It is virtually impossible for the specifier, buyer or installer to distinguish a 'good' fire door from a 'bad' one. Even the provision of a fire test report is no guarantee of performance. Without dissecting a door it is impossible to confirm that the construction of the door supplied is the same as that tested. The situation becomes more confused when variations in glazing, ironmongery, leaf size, frame specification and intumescent protection become part of the equation. Misconceptions among all parties in the specification-supply chain are rife.

Regulations exist but, as recent prosecutions have exposed, they can fail to guarantee that a door will necessarily comply with its stated fire resistance. The great majority of fire doors are not supplied as doorsets. Legislation does not span supply and installation.

What is a fire door?

Building Regulations Approved Document B defines a fire door as 'A door or shutter, provided for the passage of persons, air or objects, which together with its frame and furniture as installed in a building is intended (when closed) to resist the passage of fire and/or gaseous products of combustion, and is capable of meeting specified performance criteria to those ends'.

While this description is cumbersome, it is significant because it stresses that all elements must perform. The door, as assembled, is only as good as its weakest link. Furthermore, the tradesman who fits it is often unaware of his responsibilities. For example, planing to make it fit can jeopardise its fire resistance. Fitting instructions are rarely supplied.

Testing

A valid test report to bs476: Part 8 or Part 22, is required by law for each door design. The time, temperature and pressure conditions simulate a severe fire after flashover. Testing must be conducted on full-size specimens up to 3m x 3m in a namas-accredited laboratory. The performance is quoted in the number of minutes that elapse before failure, normally 30 or 60 minutes.

However, the test only indicates the fire performance of one door on one day. There is currently no regulation requiring re-testing. Some designs on the market still rely on the evidence of tests carried out 20 years ago. Can the manufacturer guarantee that the design has remained unmodified, that the materials and components are the same and that there have been no changes in production methods over that period?

Third-party certification

The Q-Mark fire door scheme operated by bm trada provides third-party verification that all the technical and regulatory requirements are met and that the doors are manufactured consistently to the same high standard. The Q-Mark is recognised by the Loss Prevention Certification Board, which operates within the framework of the Loss Prevention Council.

To gain the Q-Mark manufacturers must:

demonstrate type testing and assessment of all designs

check raw material quality, eg timber and hardwood lipping densities

operate an iso 9000 management system to give traceability and consistency of production

subject the production process to regular audits by bm trada

plug or label each door with the bm trada identification

provide full instructions for hardware and fitting

submit production doors for periodic audit testing to check the quality system.

A colour-coded plug on the door edge indicates its fire resistance rating, evaluated in accordance withbs 476: Part 22. The bm trada plug incorporates a coloured tree in the centre. A red tree means the builder must fix intumescent material on site following the manufacturer's instructions; a green tree means intumescent material was fitted during production - see illustration. The plugs are only issued to members of the bm trada Q-Mark fire door scheme.

Looking to the future, bm trada is working on an electronic data tagging system. Microchip transponders embedded in the door leaf and door frame will record all the information about the door from manufacture to installation. The chips are interrogated using a small hand-held reader. This system will provide complete traceability, a major benefit when a building is subsequently refurbished.

Misconceptions about fire doors

Fire doors with a 20-minute fire resistance do not need intumescent strips: in the majority of cases they do.

Fire doors must have 25mm door stops: the size of the door stop is immaterial.

Smoke seals stop smoke: they stop cold smoke but not hot smoke.

Door perimeter gaps are not important: they are critical, with 4mm the maximum.

You can fit glazing in any fire door: no, only if it is specially designed for it.

Points to watch

Oversized door leaves trimmed to size - for the majority of designs, as soon as a saw has been put into them, any test reports will be null and void

Indicative tests used to substantiate performance - such tests are only applicable for product development. Ensure a full fire test report.

Softwood frames used for one- hour fire doorsets - frames should be hardwood unless specific test evidence covers a softwood.

'Mix and match' doorset components - you cannot rely on evidence from one test for performance on a different mix of components.

Jeremy Vibert is manager, Fire Protection Products, at bm trada Certification, tel: 01709 720215 or 01709 563091. Free seminars on fire doors are available to practices

UPGRADING FIRE PERFORMANCE

To upgrade building performance a new doorset is usually preferable. For special doors, eg in historic buildings, upgrading may be possible to 20 or 30 minutes resistance. See Fire Resisting Doorsets by Upgrading. trada Technology, tel: 01494 563091. 4pp. £3.00

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