LONG BEFORE ANYONE put a cautering wand up anyone else’s patoot, the dangers of flammable* bowel gas were well known. If you let manure sit, as any farmer can tell you, bacteria will break it down into more elemental components. Some of these are of value to farmers as fertilizer, which they can pump from their manure pit out onto their crops.? Others—hydrogen, say, and methane—will blow the roof off the hog barn. Here is the Safe Farm Program channeling Beatrix Potter in a methane-safety radio spot: “It has no smell. It has no color. It often lurks about, but fails to leave a trace.”
Methane and hydrogen are explosive in concentrations higher than 4 to 5 percent. The foam on liquid manure in pits is 60 percent methane. Farmers may know this, but their families sometimes don’t. Which explains why the University of Minnesota Extension Service’s farm safety curriculum includes instructions for a children’s classroom Manure Pit Display. (“You will need: . . . toy cow, pig, and bull [1/32 scale], an aquarium, one pound of dry composted manure . . . and chocolate kisses . . . to simulate manure on top of floor [optional].”) Like a Manure Pit Display, the human colon is a scaled-down version of a biowaste storage tank. It is an anaerobic environment, meaning it provides the oxygen-free living that methane-producing bacteria need to thrive. It is packed with fermentable creature waste. As they do in manure pits, bacteria break down the waste in order to live off it, creating gaseous by-products in the process. Most voluminously, bacteria make hydrogen. Their gas becomes your gas. Up to 80 percent of flatus is hydrogen. About a third of us also harbor bacteria that produce methane—a key component in the “natural gas” supplied by utility companies. (At least two-thirds of us harbor a belief that methane producers’ farts burn blue, like the pilot light on a gas stove. Sadly, a YouTube search unearthed no evidence.) The flammability of methane and hydrogen is part of the reason for the seeming overkill of protracted bowel-cleansing that precedes a colonoscopy. When gastroenterologists find a polyp during a screening, they will usually remove it while they’re in there, using a snare with an electrocoagulating option to staunch the bleeding. They do not want to worry about igniting a rogue pocket of combustible gas—as happened in France, in the summer of 1977, to fatal effect.
At a university hospital in Nancy, a sixty-nine-year-old man arrived at the Services des Maladies de l’Appareil Digestif (French for “Gastroenterology Department”). With the current set to 4, the doctor began a simple polypectomy. Eight seconds into it, an explosion was heard. “The patient jerked upwards off the endoscopy table,” reads the case report, and the colonoscope was “completely ejected” (French for “launched from the rectum like a torpedo”).
What was strange was that the Frenchman had followed his colonoscopy prep instructions to the letter. The culprit, in this case, had been the laxative. The staff had prescribed a solution of mannitol, a sugar alcohol similar to sorbitol, the likely laxative agent in prunes. Though the man’s colon contained no fecal matter, it still contained bacteria, hungry bacteria that feasted on the mannitol and produced enough hydrogen to set the stage for an internal Hindenburg scenario. A study done five years later found potentially explosive concentrations of hydrogen or methane, or both, in six out of ten patients prepped with mannitol.
This is no excuse for putting off your colonoscopy. Mannitol is no longer used, and doctors routinely blow air or nonflammable carbon dioxide into the colon as they work, which dilutes any pockets of hydrogen or methane. (Inflating the colon also helps them see what they’re doing. And creates the magnificent, billowing flatulence that rings through the colonoscopy recovery room.) Outside the body, intestinal hydrogen and methane pose no danger. The act of passing flatus dilutes the gases, mixing them with the air in the room and lowering the concentration to levels well below combustibility. As anyone who has typed pyroflatulence into YouTube is aware, the match would have to contact the gas the second it’s blown from the body.
In the early days of the space program, NASA fretted about flammable astronaut flatus building up inside the tiny, hermetically sealed space capsules. A researcher presenting at the 1960s conference “Nutrition in Space and Related Waste Problems” was concerned enough to suggest that astronauts be selected from “that part of our population producing little or no methane or hydrogen.” NASA used to keep flatus expert Michael Levitt—whom you’ll meet shortly—on retainer as a consultant. Levitt assured them the capsules were large enough and the air inside sufficiently well circulated that intestinal contributions of hydrogen and methane were unlikely to reach a dangerous concentration. NASA was understandably wary. An earlier decision to circulate 100 percent oxygen in the capsules led to the deaths of all three Apollo 1 astronauts when a spark ignited a fierce fire during a launch-pad test.