I know your wife might not believe it, but the human body alone doesn't produce toxic gases :wink:. Although Methane (in farts) is flamable :timebomb:.
There was a story a while back where a woman that had died was brought into a hospital and people got sick that were in the same room. I think that they figured out that she had ingested some poison that reacted in the body.
I read in the Darwin Awards a few years ago where a very large man gassed himself to death while sleeping in a tightly closed bedroom. I think his main diet was cabbage and beans or something. I believe this has been debunked and proven to be impossible.