Gulp: Adventures on the Alimentary Canal

Roach explores the combustible nature of gases produced by human and animal digestive systems in this chapter on flammable bodily emissions. The discussion begins with agricultural contexts, explaining how bacteria in manure pits create dangerous concentrations of hydrogen and methane that can explode and destroy farm buildings. This same bacterial process occurs within the human colon, an oxygen-free environment where bacteria break down waste and produce gaseous byproducts, primarily hydrogen and methane.

The chapter examines medical implications of these flammable gases through historical case studies. Roach recounts a 1977 incident in France during which a colonoscopy patient experienced an internal explosion when doctors used electrical equipment to remove a polyp. The patient had consumed mannitol, a laxative that hungry bacteria converted into hydrogen gas. This dangerous scenario led to changes in medical practices, including the abandonment of mannitol-based preparations and the routine use of non-flammable carbon dioxide to dilute potentially combustible gases during procedures.

NASA’s concerns about astronaut flatulence in sealed spacecraft capsules illustrate another practical application of this knowledge. Space agency officials worried that hydrogen and methane could accumulate to dangerous levels in small, hermetically sealed environments, leading them to consult experts on intestinal gas production.

Roach presents curious historical cases of flammable belching, particularly an 1890 British case documented by Dr.