Toyota Prius Owner's Manual page 350

3-1. Using the air conditioning system and defogger

Ventilation and air conditioning odors

To let fresh air in, set the air conditioning system to the outside air mode.

During use, various odors from inside and outside the vehicle may enter
into and accumulate in the air conditioning system. This may then cause
odor to be emitted from the vents.

To reduce potential odors from occurring:
• It is recommended that the air conditioning system be set to outside air
mode prior to turning the vehicle off.
• The start timing of the blower may be delayed for a short period of time
immediately after the air conditioning system is started in automatic
mode.

Customization
Settings (e.g. switching between outside air and recirculated air mode linked
to "AUTO" switch operation) can be changed.
(Customizable features P. 603)
CAUTION

To prevent the windshield from fogging up
Do not use
The difference between the temperature of the outside air and that of the
windshield can cause the outer surface of the windshield to fog up, blocking
your vision.
NOTICE

To prevent 12-volt battery discharge
Do not leave the air conditioning system on longer than necessary when the
hybrid system is not operating.
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during cool air operation in extremely humid weather.