The LWF Blog
Access and Facilities for Fire Fighters | Pt 2 – Inside the Building
October 23, 2013 11:05 amFire service personnel faced with the task
of tackling a blaze high above the ground or deep in a basement need to reach
the fire quickly, with all of their equipment. Getting there should not be so
arduous that they have no strength left to fight the fire. Ensuring your
building is fire safe should begin at the design and renovation stage of a
project with the inclusion of such fire protection measures as fire-fighting
shafts and adequate venting.
Fire-fighting shafts
The physical safety of fire fighters and
building occupants, plus the preservation of the building and its contents, may
be jeopardised by any delays in reaching the fire floor. Since most fire
brigades now carry ladders on their vehicles that only reach up to 11m, a fire
in buildings with a storey-height greater than 11m will generally be fought
internally.
The time taken to carry fire hoses up stairs
inside the building, or down into a basement can be considerable. For this
reason, the British Standard requires that the following sizes and types of
building should all feature fire-fighting shafts.
Type of building
|
Recommended content of fire-fighting shaft
|
Buildings or parts of buildings where the |
Fire-fighting stair Fire-fighting lobbies provided with a fire Fire-fighting lift installation |
Buildings where the depth of the surface |
Fire-fighting stair Fire-fighting lobbies provided with a fire Fire-fighting lift installation |
Buildings with a height of 11m or more, |
Escape stair Unvented fire-fighting lobby provided with |
Buildings intended to be used as shops, |
Fire-fighting stair Fire-fighting lobbies provided with a fire |
Buildings where there are two or more |
Fire-fighting stair Fire-fighting lobbies provided with a fire |
Fire-fighting shafts generally consist of
three main areas: stair, lift and lobby. Fire-fighting stairs are designed to
be sufficiently wide to allow fire-fighting personnel to carry their equipment
up and down stairs; but the size and weight of some of this equipment – combined
with the building’s height – may make a fire-fighting lift necessary. This type
of lift differs from a normal passenger lift, in that it is designed to
operate, for as long as is practicable, when there is a fire in parts of the
building beyond the confines of the fire-fighting shaft.
The construction, design and installation of
fire-fighting lifts now have to conform to the new European standard BS EN
81-72. The final approach to the fire floor is by means of the fire-fighting
lobby. These areas are designed to be large enough to allow the fire service to
lay fire-fighting hoses to connect to the fire-main outlet (if provided)
without undue congestion, but not so large as to encourage any form of storage
or other unauthorised use. These lobbies also represent a safe route of egress
should the lift fail, and they provide a safe area on the floor below the fire
floor, where fire fighters can assemble their equipment before starting to
tackle the fire.
To minimise the possibility of serious
contamination of the shaft by toxic products during a fire it is necessary to
provide a form of smoke control within the protected stairs and lobby. Natural
smoke vents are one way of doing this.
Fire-fighting provisions within building
|
Openable vent |
||
Fire-fighting stair or lobby |
Position of stair or lobby
|
Vent area m2 |
Position of Vent |
Stair |
On an external wall |
1.0 |
At each storey |
Stair |
Not on an external wall |
1.0 |
At top of stair |
Lobby |
Above ground level on an external wall |
1.5 |
Near to ceiling direct to open air |
Lobby |
Above ground level not on an external wall |
1.5 |
At each storey to a smoke shaft |
Lobby |
At each basement level |
1.0 |
High level direct to open air or to a |
When activated, the vents help to remove any
toxic gases, minimising the possibility of serious contamination of the stair
and lobby. Venting may then improve visibility and reduce temperatures, which
would make search, rescue and fire-fighting easier.
Venting of Basements
Basement areas present a significant
challenge to fire-fighting operations due to the tendency for heat and smoke to
build-up within access routes i.e. stairs. For this reason, basement areas that
are in excess of 200m2, and 3m or more below ground level, require ventilation to improve
conditions for fire-fighting operations.
Basement ventilation can be achieved either
by providing sufficient natural vents to allow smoke and hot gases to escape or
by providing a mechanical extraction system. It should be noted that where a mechanical
extraction system is proposed a sprinkler system would also be required to
control fire sizes.
Natural vents for basement ventilation
should provide a clear cross-sectional area of not less than 1/40th of the
floor area of storey that they serve and should be distributed around the
perimeter of the building. Mechanical smoke extraction systems should be
designed to achieve at least 10 air changes per hour.
Fire-fighting access and facilities should
be selected and designed to assist the fire service in protecting life,
reducing building losses, salvaging property and goods, and minimising
environmental damage.
It is critically important that all these
points are considered when reviewing an existing building or designing a new
one. Early consultation with the fire authority is critical for awareness of
any requirements that they may have, and any additional policies demanded in
local legislation.
LWF can provide specialist advice on how
compliance with the design standard may be achieved, or – if feasible and
advantageous – an alternative, performance-based approach could be considered.
To discuss this article further or for an
appointment with one of LWF’s fire engineers please call Peter Gyere on 020
8668 8663.
Lawrence Webster
Forrest are fire engineering and fire risk management consultants with over
twenty years experience in the development of fire engineered technology and
the application of fire safety standards including fire engineered techniques.