Should work for anything expelled from the body.

But -- flatulence isn't gases dissolved in the blood, it's pockets of gas trapped in the gut, sort of an X-0-X-0 type of deal. The gas can come from many sources, including mouth breathing and carbonated drinks (that includes beer). It is usually a combination of gases, including CO2 and that's heavier than air (picture the "smoke" coming off of dry ice).

It's not a simple problem. However, if you breathe enough helium, will you float away, squeaking for help?