Ford 1999 Crown Victoria Owner's Manual page 116

Starting
Guarding against exhaust fumes
Although odorless and colorless, carbon monoxide is present in exhaust
fumes. Take precautions to avoid its dangerous effects.
If you ever smell exhaust fumes of any kind inside your vehicle,
have your dealer inspect and fix your vehicle immediately. Do
not drive if you smell exhaust fumes. These fumes are harmful and
could kill you.
Have the exhaust and body ventilation systems checked whenever:
the vehicle is raised for service.
the sound of the exhaust system changes.
the vehicle has been damaged in a collision.
Engine exhaust, some of its constituents, and certain vehicle
components contain or emit chemicals known to the State of
California to cause cancer, and birth defects or other reproductive
harm.
Important ventilating information
If the engine is idling while the vehicle is stopped in an open area for
long periods of time, open the windows at least 2.5 cm (one inch).
Adjust the heating or air conditioning (if equipped) to bring in fresh air.
Improve vehicle ventilation by
keeping all air inlet vents clear of
snow, leaves and other debris.
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