Honda Prelude 1990 Online Reference Owner's Manual page 64

Engine Exhaust Gas Warning
A properly maintained car is your best protection against exhaust
gas entering the passenger compartment.
The exhaust system should be thoroughly inspected by a
competent mechanic whenever:
The car is raised for an oil change.
You notice a change in the sound of the exhaust.
The exhaust system or the rear or underside of the car is
damaged.
Avoid breathing exhaust gases. They contain carbon monoxide,
which is a colorless, odorless gas that can cause loss of
consciousness and eventual death. If you suspect that exhaust
gas is entering the passenger compartment, have the cause
determined and corrected as soon as possible. If you must drive
under these conditions, drive only with all windows fully open.
Do not drive with the trunk lid open. An open trunk may draw
exhaust gases into the passenger compartment. If you must
drive with the trunk lid open, drive only with all the windows
wide open.
Do not run the engine in confined areas, such as garages, any
longer than necessary to move the car in or out.
If you must sit in a parked car with the engine running for more
than a short time, adjust the heating/ventilation system as
follows:
1. Push the
2. Set the temperature lever for best comfort.
3.Turn the fan to the highest speed.
NOTE:
To insure proper operation of the car's ventilation system, keep the
front air inlet clear of snow, mud, leaves or other obstructions.
and buttons on.