Question: Is it safe to ignite farts?
Short answer: Usually.
Long answer: Today’s question comes to us from a reader with a keen interest in pyroflatulence. This is the traditional practice of igniting farts, which has now been documented in a number of videos. The chemical principles behind this phenomenon have already been covered in an outstanding Wikipedia article, which we recommend highly to curious readers.
The question concerns the tradeoff between entertainment value and safety. There are many reported incidents of people injuring themselves while igniting farts, as well as at least one case of a fart causing an explosion during surgery.
Under normal circumstances, the issue comes down to positioning. To successfully light a fart, one has to place the flame close enough to the source to ignite the gas. But for the farter to escape injury, the flame has to be at a safe distance from clothes or anything else that might catch fire. As a public service, we have therefore attempted to evaluate the safety profile of pyroflatulence.
The ignitability of farts is probably due to their hydrogen sulfide content, which produces the characteristic fart smell and is also highly flammable. It has a lower flammability limit of 4.3%, which corresponds to the proportion of gas that must be present for ignition to take place.
In our experiments, a typical fart spreads slowly throughout the volume of our collection tube, eventually reaching an equilibrium:
Source
https://flatology.com/fire-clouds/
