This is a old air tank that I use for starting fires and for filling my air cannon.
This tank was made with parts that where on hand a many many years ago. I had to take it apart because of a small leak and wanted to show how it was made.
Precautions Use an EMPTY propane tank. You don't want gas leaking out and causing an explosion. Also compressed air can be dangerous. I'm not sure what a propane tank is rated for but keeping the PSI at a reasonable amount should be OK.