What type of pipe should not be used in steam heating?

There are a lot of kinds of pipe that should not be used for steam heat. If you are using steam having a pipe burst can burn or even kill people in the house. It's not something to treat lightly so you should be very careful and use pipe that is rated for both the temprature and pressure of your heating system. If you don't know then please please please call a professional. Take it from someone who has suffered through 3rd degree burns. It is so not worth a burn debridement.