Miele DA 420 V Operating And Installation Instructions 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 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 must be
sought.
If the rangehood is being operated in
recirculation mode, the above
restrictions do not apply.
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