Seat Leon Owner's Manual page 143

142 Air conditioning
CAUTION
Do not smoke when air recirculation is switched on in vehicles with an air
conditioner. The smoke taken in could lie on the cooling system vaporiser
and on the activated charcoal cartridge of the dust and pollen filter, leading
to a permanently unpleasant smell.
Note
Climatronic: Air recirculation mode switches on to prevent exhaust gas from
entering the vehicle interior when it is in reverse and while the automatic
windscreen wash and wipe is working.
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