Lexus RX400h2006 Owner's Manual page 301

AIR CONDITIONING
To switch air intake mode manually —
The air intake control button is used to switch between the
OUTSIDE AIR mode and the RECIRCULATED AIR mode.
With the button set to the OUTSIDE AIR mode, the indicator
light will turn off and the system will take fresh outside air into
the vehicle.
To quickly circulate cooled air, push the air intake control button
for RECIRCULATED AIR. The indicator light will come on.
For normal use, it is best to keep the air intake control button
set to the OUTSIDE AIR mode. If recirculated air is used during
heating, the windows fog up more easily.
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To prevent the windshield fogging, the air intake mode may
change automatically to the OUTSIDE AIR mode depending
on the air conditioning system.
For example, when the ambient temperature is low, the air
intake mode may change automatically to the OUTSIDE AIR
mode. This is not a malfunction.
When the air conditioning is on, if the engine coolant
temperature or electric compressor inverter temperature
becomes extremely high, the RECIRCULATED AIR mode is
automatically selected. In this case, it is not possible to return
to the OUTSIDE AIR mode. This is not a malfunction. When
the engine coolant temperature or electric compressor inverter
temperature is lowered, the previous mode resumes.