What kind is it?

Getting my gear set up to start kegging and a friend gave me an old cylinder. Nice big steel one. Problem is he does not remember for sure if it was for co2 or for nitrogen. He is fairly sure it was his nitrogen tank. How can I tell them apart since there are no tags or stickers on the cylinder?

Second question. I looked at the stamps on the cylinder and the last one was from 1988. Looks like its been sitting in the garage for a long time. Is this tank still any good? Or should I just take it into Airgas and see if they will exchange it?

Airgas should be able to tell you if it was CO2 or N2, and stamp if it still certifies.

So I guess your overall answer is take it to Airgas.

Yeah, any place that fills them can tell you what it's for and pressure test it to re-certify.

CO2 threads are on the outside. Beer Gas Tank (N2/CO2 mix) threads on the inside. Needs to be re-certed no matter what.

Thanks guys. The threads on this one are on the inside. I think i'll take a long lunch and swing by Airgas today.