Miele ABLG 202 Installation Instructions Manual page 7

Warning and Safety instructions
In order to ensure safe operation and to prevent gases given off by
the heating appliance from being drawn back into the room, when
the external motor and the heater are both operated
simultaneously, an underpressure in the room of 0.04 mbar (4 Pa)
is the maximum permissible.
Sufficient ventilation can be maintained by air inlets which cannot
be blocked, e.g. in windows, doors and outside wall vents. The
diameter of the inlet openings must enable sufficient ventilation. 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 should be sought.
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