1993 Pontiac Firebird Owner's Manual - Page 240

To Add Coolant to the Recovery Tank: If you need more coalant, add the proper mix at the coolant recovery tank, but only when your engine is cool. If the tank is very lowor empty, also add coolant to the radiator. See the followingprocedure and referto "Engine Overheating" in the Index. - Turning the radiator pressure cap when the engine and radiator are hot can allow steam and scalding liquids to blow out and burn you badly. Never turn the pressure cap - even a little when the engine and radiator ar hot. Add coolant mix at the reovery tank, but be careful not to spill it. You can be - L coolant on hot engine parts. Coolant contains ethylene glycol, and it will bum if the engine parts are hot enough. Don't spill coolant on a hot engine.