Miele downdraft extractor Instruction Manual page 8

Warning and Safety instructions
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 cooker hood 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 or outside wall vents, or by other
technical measures, such as ensuring that the cooker hood 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 qualified gas fitter (registered with an official gas safety
body in accordance with national safety regulations, GasSafe in
the UK) must be sought.
If the cooker hood is used in recirculation mode, where the air is
directed back into the room in which it is located, operating a
heating appliance which depends on the room air at the same
time is no cause for concern.
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