Cadillac 2001 Catera Owner's Manual page 268

CAUTION:
Operating the engine with the air cleaner/filter
off can cause you or others to be burned. The air
cleaner not only cleans the air, it stops flame if
the engine backfires. If it isn't there, and the
engine backfires, you could be burned. Don't
drive with it off, and be careful working on the
engine with the air cleaner/filter off.
NOTICE:
If the air cleaner/filter is off, a backfire can
cause a damaging engine fire. And, dirt can easily
get into your engine, which will damage it.
Always have the air cleaner/filter in place when
you're driving.
Passenger Compartment Air
Filter Replacement
The passenger compartment air filter traps most of
the pollen from the air entering your vehicle. Like
your vehicle's air cleaner filter, it may need to be
changed periodically. For how often to change the
passenger compartment air filter, see your Maintenance
Schedule booklet.
6-17