Doreatha, it sounds to me like you have steam heat, and not forced hot water heat. A radiator in a house with steam heat will have only one pipe leading into the radiator. On the other side of the radiator, will be a steam valve, like the one you described. When the heat is on and the radiator is hot, the valve may open with a pssstt type sound, releasing some of the steam pressure. Also, you can often tell a steam system by looking at the boilerr in your basement. There should be a sight-glass, (small narrow glass tube), filled at least half-way with water, depending on your system. This is a dead giveaway for a steam system. Talk to your maintenance person about its care...whole other subject. Anyway, a house with forced hot water will have a radiator with two pipes, (one at each end). leading into and out of the radiator. You do not have to, (nor can you), bleed a steam radiator. However, a forced hot water radiator can and should be bled. The bleeder fitting is on the top and side of the radiator, usually the opposite side from the open/shut valve. Follow Renee's fine instructions and you will have quiet, warm, and efficient radiators.