Chevrolet 1999 Monte Carlo Owner's Manual page 224

The tethered cap is behind a hinged door on the driver's
side of your vehicle.
While refueling, let the cap hang by the tether below the
fuel fill opening.
To remove the cap, turn it slowly to the left
(counterclockwise). The cap has a spring in it; if you let
go of the cap too soon, it will spring back to the right.
6-6
CAUTION:
If you get gasoline on yourself and then
something ignites it, you could be badly burned.
Gasoline can spray out on you if you open the
fuel filler cap too quickly. This spray can happen
if your tank is nearly full, and is more likely in
hot weather. Open the fuel filler cap slowly and
wait for any "hiss" noise to stop. Then unscrew
the cap all the way.
Be careful not to spill gasoline. Clean gasoline from
painted surfaces as soon as possible. See "Cleaning the
Outside of Your Vehicle" in the Index.
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