Much like its bigger brother, the Combustion Furnace, a Combustion Generator makes power by burning things. However, in the case of the Combustion Generator, it specifically burns gaseous or liquid fuel, creates toxic smoke that needs to be filtered out of the atmosphere in most cases, requires oxygen to work at all, and is an active fire hazard for any flammable gases in the air. On the other hand, it can run on a canister of burn mix for an extremely long time (and as this includes its own oxygen, this means it can be placed outside of your enclosed environment, letting the toxic smoke dissipate into space.