I think he's using anhydrous ammonia. It's commonly used in agriculture and back before the Mexican cartels cornered the meth market, it was frequently stolen by crystal cooks in the U.S.
But here's the issue: If you're eyes are exposed to a concentration of the gas, you're blind.

I think it's kind of the same thing with your lungs, except you're dead. It sucks all the moisture out.
I'll stick with steam.
T