| A
building’s air transfer system e.g. in an office block building
needs to allow the circulation of air thus keeping the air quality
levels up, but also needs to control the temperature e.g. to keep
a comfortable working temperature and not to increase energy costs
by losing heat. The air transfers system may use fan assisted ventilation
ducts, or a natural effect e.g. ‘stack effect’ (a temperature
induced method of making the different internal pressure differentials
work so that the warm air can rise up through the building –
using ventilation grills as part of the system). Some important
points to make about the air transfer system and it use of grills
/ grilles are:
- The grills may be
used e.g. in timber doors, stud walls, some duct terminals within
(not on the boundary of) fire protected route. The apertures /
spaces made in walls in doors for ventilation purposes therefore
also provide a possible route for fire and smoke and therefore
steps need to be taken to contain the fire and smoke effectively
e.g. using Intumescent Grills.
- A ventilation grill
generally consists of the grill itself and the faceplate(s).
- Hot air expands and
the higher pressure means that the hot (high pressure) air will
naturally try to flow towards cooler (low pressure) air. The implications
of this are that air transfer systems have to be able to maintain
the right pressure differential balance, and all gaps created
in the fitting of grills which could be exploited by fire and
smoke need to be adequately addressed.
- Even though intumescent
materials can be used effectively in the systems their expansion
is activated by heat. ‘Cold smoke’ aspects therefore
could be combated by using e.g. smoke seals or electro-mechanical
systems linked to smoke detectors alongside the intumescent ‘failsafe’
part of the system.
Intumescent
Ventilation Grills
The benefit
of ventilation grills made from intumescent material is that this
material’s natural and normal reaction to temperatures (associated
with fires) is to expand in volume well beyond their normal size
to create a large amount of char which restricts flames, gases and
smoke.
The openings
in Fireplug Intumescent Ventilation Grills for example will provide
a good level of free airflow in normal use (50% for 100 x 100mm
and 76% + for 300 x 300 mm) but will seal up under the action of
heat during a fire. These are used in conjunction with Fireplug
FP Pressed Steel Louvered Faceplates. Fireplug FPG suit most fire
doors and the Fireplug FP (faceplates) can be easily surface mounted
on either side. It’s important to cut a hole which provides
a snug fit and in composite doors it’s recommended that the
internal faces of the aperture are framed with a dense hardwood.
Intumescent Mastic can be placed between the grill and the wood
if needed. |