Hissing vent on a steam heating pipe

This is basically going to be landlord work unless you plan playing heating technician and checking the basement pipes. Here's the gist:

• Air vents on the radiator must flow air out so it can be replaced by steam to heat. They sometimes have adjustment valves on them so you can balance the system.
• Air vents that are producing a lot of noise are either
  • too small of a vent
  • clogged up / broken (this is you because you're leaking steam)
• Improperly designed systems can also push a lot of air out of the radiators. The steam delivery pipes should also have air vents on them before the radiators.

When working properly, those air valves should not let steam through. They should close when the steam reaches them, and open when there isn't steam. If there are showing visible steam, they need replacement.

I found this to be a good article on caring for steam vents that will provide more detail.

You need someone that knows exactly how the near-boiler piping should be. Even a slight change in the diameter, the height above the water line, or the return system will affect the system's operation.

Also, on a one pipe steam system, the maximum steam pressure should not exceed 3 psig. The output of the new boiler should exceed the connected piping and radiation load by about 33%. On a steam system the boiler size is dictated by the connected load and not the heat loss of the building.

All radiator valves on a 1 pipe steam system are only for isolation of that radiator and need to be fully open or fully closed; no partially open/closed steam valves. Steam vent choice is also critical. Again, I say again, you need someone who knows steam piping and most people in the business do not!!! I rattled on about piping and etc. and forgot to answer the original question. Yes you can use baseboard radiation on a one pipe steam system. the minimum pipe/radiation size is inch and 1/4 if a short run or preferable 2".