They were popular during WWII (or maybe it was the depression) I believe, when fuel was scarce and expensive. They're really tough to get working well. Ideally, the gas will come out almost perfectly clear. The smoky looking gas you see coming out in the show will eventually gum/soot up their engine (as you could see the soot on the top of the barrel when they tried it the first time). There are several publications out there that outline how to make one (a better one even).It's on now, I'd never seen the Gasifier stove, learned something useful tonight.
May sound stupid, but does anyone think this is the governments idea to see how smart the general public is in case everyone nukes each other.