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Warning - danger of toxic fumes
Great care should be taken when
using the cooker hood at the same
time and in the same room or area of
the house as another heating appliance
which depends on the air in the room.
Such appliances include gas, oil, wood
or coal-fired boilers and heaters,
continuous flow or other water heaters,
gas hobs, cookers or ovens which draw
air in from the room and duct exhaust
gases out through a chimney or
extraction ducting.
When used in extraction mode, with or
without an external motor, the appliance
draws air in from the room in which it is
installed
from neighbouring rooms.
If there is insufficient air, an
underpressure will occur. The heating
appliance may be starved of oxygen,
impairing combustion.
Harmful gases could be drawn out
of the chimney or extraction ducting
back into the room, with potentially
fatal consequences.
In order to ensure safe operation, and
to prevent gases given off by the
heating appliances from being drawn
back into the room when the extractor
and the heater are in operation
simultaneously, an underpressure in the
room of 0.04 mbar (4 pa) is the
maximum permissible.
Ventilation can be maintained by air
inlets which cannot be blocked, in
windows, doors and outside wall vents,
or by other technical measures, such
as ensuring that the extractor can only
be switched on when the heating
appliance is switched off or vice versa.
A ventilation brick alone is not generally
sufficient to ensure safe ventilation.
The overall ventilation condition of
the dwelling must be taken into
account. If in any doubt, the advice
of a competent builder or, for gas, a
"Corgi" installer, must be sought.
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