The general information below is intended as a general guide
and should not be taken as current legislation regarding specification
and regulations for compliance for Building control. The information
was extracted on 8th June 2008 from The
Fire Safety Advice Centre .
Please refer to thier website and seek advice from your local
building control officer regarding new updated information and
new regulations that may apply
Buildings are compartmented to delay the spread of fire from
one area to another. The compartments are usually linked by doors
to allow for passage of ‘traffic’ around the building.
Doorsets have two important functions in a fire, when closed
they form a barrier to fire spread and when open they provide
a means of escape.
A well designed timber fire door will delay the spread of fire
and smoke without causing too much hindrance to the movement
of people and goods. Different parts of a building may be separated
from each other, into compartments of a fire-resisting construction.
Any openings leading from them will have fire doors to maintain
an effective fire barrier and should prevent excessive transmission
of products of combustion which can interfere with the safe use
of escape routes. Every fire door is therefore required to act
as a barrier to the passage of smoke and fire to varying degrees
dependent upon its location in a building and the fire hazard
associated with the building. Consequently the functions of a
fire doors is, to provide adequate resistance to the passage
of smoke and other combustion products during the early stages
of a fire. Secondly to provide a barrier to a well-developed
fire without permitting fire and excessive quantities of smoke
to pass. Some doors may be required to fulfil only the first
function as they may not be subjected to the full severity of
a fire because of their location; others may have the main aim
of resisting fire penetration as indicated by the second function.
Some may have to meet both requirements. At present, fire doors
are specified as smoke-stop doors when required to fulfil the
first function and fire-check and fire-resisting doors to fulfil
the second.
Specifications of timber fire doors
The performance of timber doors is judged by subjecting them
to the standard test procedure specified in BS 476 : Part 22:
1987 or BS EN 1634-1: 2000. Tests are made on complete door assemblies,
the door and frame with all the necessary hardware. It is then
fixed in a wall representing its use in practice. By testing
a door in one type of frame and using it in another, no guarantee
can be given of its behaviour under fire conditions.
The test procedure is fully described in the Standard and consists
of exposing one face of the door to heat condition expected in
a fire whilst observing the door for stability and integrity.
The Standard requires the tests to be carried out with the upper
part of the door under a small positive pressure, to simulate
the conditions likely to occur in a fire. It also provides an
objective method of establishing the loss of integrity of a door
by the use of a combustible fibrous pad on the un exposed side
of the door and see when it ignites. A door should be tested
from each side to establish its performance with either face
exposed to fire conditions, consequently requires two specimens.
It is reasonable assumed all fire doors and frames manufactured
to the same specification as the two specimen doors and frames
will achieve the same fire resisting properties.
Over the last few years a technique has been developed for minimising
the susceptibility of door edges to early penetration by fire.
It consists of applying intumescent strip to the edges so that
a rise in temperature will cause the material to swell and close
the gaps. Intumescent paints have been used but the most successful
and reliable technique is the intumescent strip, about 4 mm thick
by 10 mm wide, cut into a groove in the door or the frame edge.
As soon as the temperature in the vicinity of the strips exceeds
200 degrees C, usually about 10-15 minutes after the start of
a fire, the strip swells and seals the gaps. One strip is adequate
for a half hour fire door and for the increased protection needed
with one-hour doors, two of these strips will be necessary. The
intumescent material is soft and cellular in structure and will
not prevent deformation of the door.
There are fire resisting doors that are able to resist the passage
of fire for more than 30/60 minutes but these are more likely
to be used for the protection of property than for means of escape
from fire.
| Fire check and fire resisting doors - Door type |
Integrity [1]
Minutes |
Stability [2]
Minutes |
| Half-hour fire-check |
20 |
30 |
| Half-hour fire-resisting |
30 |
30 |
| One-hour fire-resisting |
45 |
60 |
| One-hour fire-resisting |
60 |
60 |
[1] Integrity Failure is deemed to occur
when cracks or other openings exist through which flames
or hot gases can pass or when flaming occurs on the unexposed
face.
[2] Stability Failure is deemed to occur
when collapse of the specimen takes place.
Identifying Fire Doors
Identifying fire doors is very difficult, however responsible
door manufacturers label their doors. This will identify the
manufacturer, the date of manufacture and the design fire rating
of the door type. They may fit a colour coded plug instead of,
or in addition to, the label. Identification labels are usually
fitted on the top or hanging edge of the door and plugs in the
long edges. For Hospitals, fire doors display a disc at the top
of each face of the door showing the design fire performance
see HTM58. Identification marks are sometimes removed during
installation, or adjustment of the assembly and may have been
painted over.
All dedicated fire doors providing a half hour or greater performance
will be fitted with intumescent seals. These may be encased in
a PVC sheath, of any colour, which may also hold a blade or brush
seal for smoke sealing purposes. These seals are fitted in the
door leaf edges or the frame to seal the head and long edges
of the assembly. A door may be fitted with a concealed intumescent
system where the long edge sealing is housed under lippings.
Intumescent seals will be visible at the head of the door. Intumescent
seals expand under heating to seal the gaps between the door
leaf and the frame and at the meeting stiles of pairs of doors.
Doorsets using 44mm thick doors fitted with 10-15mm wide intumescent
seals are likely to be FD3O doorsets. When used with 54mm thick
doors using at least 20mm width of intumescent seal, fitted as
one or two strips, the design performance for this doorset is
likely to be FD6O. Doorsets with a rating in excess of FD6O are
rarely used on escape routes or to protect people but may be
found where property protection is important e.g. data storage
areas where documents cannot be removed in the event of fire.
Some of these doors have the appearance of timber, but may be
constructed with a mineral core. Expert assistance may be required
to identify such doorsets.
You may have documentation that is supplied with the fire door
giving you all the necessary information. Unfortunately there
is no standard method of identifying fire doors other than insisting
on written proof that a fire door meets all the necessary standards,
for example a test certificate.
British Woodworking Federation is another organisation that
provides fire door ratings and the following is their system.
Fire ratings for fire door assemblies are given in minutes and
prefixed by the letters 'FD' i.e. FD 30 equates to a 30 minute
fire door or doorset. The most commonly specified integrity levels
are:
- FD30 - 30 minutes (Half Hour)
- FD60 - 60 minutes (One Hour)
Intumescent Fire Seals
Intumescent fire seals and cold smoke
seals should be fitted to the back edge, stile and head
of the fire resisting door sets.
Fire Resisting Glazing
Ordinary glass cracks
when exposed to heat and is liable to fall out fairly early in
a fire. Safety glass can withstand exposure to the
heating condition in a fire test for at least 30 minutes before
it reaches a temperature high enough to soften it. The main reason
for this is that nearly 50 per cent of the incident heat is transmitted
through the glass by radiation.
The size of the glass and the method of its retention are important
factors which influence its integrity. As the temperature approaches
the softening point a large sheet will tend to collapse earlier
than a smaller one. On the unexposed face, beading retaining
the glass is subjected to radiant and conducted heat through
the glass and to convection currents at the top of the pane.
This can raise the temperature sufficiently to ignite timber
beading after about 20 minutes. To delay the ignition of beading
to 30 minutes it is necessary to provide protection by impregnation
of a surface coating or a surface covering of non-combustible
material.
For longer periods of fire protection, an improved retention
system for the glazing is needed, so far only non-combustible
glazing sub-frames have been shown to be satisfactory. The glass
panel should be small and the method of fixing it should ensure
that no direct path can be created for the transference of hot
gases.
Existing doors
Years ago it was accepted practice to improve the performance
of an existing door to a half-hour fire-check or fire-resisting
standard, although in some cases it was more economical to replace
the door rather than alter it. The doors were usually panel type
or a light core flush type about 35 mm thick: they require a
facing on each side with a non combustible board. This non combustible
board quite often contained asbestos which was acceptable to
use then but not acceptable now. There was no advice on improving
the performance of existing doors to a one-hour standard.
Consequently it may be necessary to replace damaged door leaves
or doorsets and in some cases, to install additional fire rated
doorsets. It is now the accepted practice to fit new fire resisting
doorsets preferably to upgrading them. There are ASDMA members
specialise in the manufacture of bespoke performance doors and
doorsets to suit customer defined requirements. Associate members
can supply many of the doorset related materials and components.
For further information please refer to the ASDMA website.
Maintenance of Fire Doors
Fire doors are engineered products that provide life and property
saving functions in the event of fire. It is important that they
are regularly inspected and maintained to permit them to perform
at their best on the one and only occasion when they are called
upon so to do.
Doorsets fitted with hold open devices or swing free type closer
should be closed daily, particularly overnight when there is
likely to be low building occupancy. For busy 24/7 buildings
(e.g. hospitals) fire doors should be closed at least weekly.
All fire doors should close effectively from any angle of opening
using only the door closer.
There are a number of reasons why doors may fail to close :-
- Check that there are no foreign bodies or other objects obstructing
the door.
- Check that any smoke seals are correctly fitted and are undamaged.
- Check the latch, if fitted to ensure correct operation and
that it is suitably lubricated.
- Only as a last resort should the closing device be adjusted,
but this must be carried out carefully to ensure that the doors
can be opened without undue force.
Intumescent seals should be checked regularly, at intervals
not greater than 6 months, and damaged or missing seals replaced.
To maintain the design performance potential, replacement seals
should be of the same brand, size and type as the original. However,
any intumescent seal of the same size as the original is better
than none.
Mechanical items such as hinges, locks, latches, closer, floor
springs etc are likely to wear over time. Maintenance provisions
should comply with the hardware suppliers’ recommendations
where these are known. Otherwise, locks and latches may require
occasional light lubrication. Some hinges use self lubricating
bearings that will not need additional lubrication.
Where it is necessary to replace worn hardware on a fire door,
the essential items listed above should be replaced with products
to the same specification as the original where possible. Otherwise
hinges, latches, locks, flush bolts, closer and other items of
load bearing or securing hardware should be of the same type
and size as the original items and should have been proven for
use in timber fire rated doorsets of the required performance.
Hardware that has been successfully tested in metal doorsets
may not be suitable for use with timber doorsets.
Redundant hardware should be carefully removed. Intumescent
gaskets may have been used under hinge blades; lock/latch for
end plates and strike plates, with some closer fittings and in
flush bolt recesses. These gaskets should be replaced if possible
with gaskets of the same material. Otherwise they should be retained
and reused with the new fittings if they are undamaged. Intumescent
gaskets or mastics used for these applications are usually the
low pressure type.
British Standards
The following is a list of documents relevant to timber fire
doors
BS 476: - 20: 1987 Fire tests on building materials and structures.
Methods for determination of the
fire resistance of elements of construction (general principles)
BS 476 - 22: 1987 Fire tests on building materials and structures.
Methods for determination of the
fire resistance of non-loadbearing elements of construction
BS 476: - 23: 1987 Fire tests on building materials and structures.
Methods for the determination of the contribution of components
to the fire resistance of a structure
BS 476: - 31.1: 1983 Fire tests on building materials and structures.
Method of measuring smoke penetration through doorset and shutter
assemblies – method of measurement under ambient temperature
conditions.
BS 8214:1990 Code of practice for fire door assemblies with non-metallic
leaves
BS EN 1634-1: 2000. which is an alternative for BS 476 - 22:
1987 |
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