A Straight Dope Classic from Cecil's Storehouse of Human Knowledge

Do you toot more at high altitude?

April 12, 1996

Dear Cecil:

Last weekend my girlfriend and I spent the night in a mountaintop lodge at an elevation of 9,000 feet, about 6,000 feet above the town in which we live. The romantic intent of the evening was slightly stifled by the fact that we both had a serious gas problem. It was distracting to have to constantly fight to hold back a fart.

It seemed odd that we both developed this problem at the same time. We didn't eat the same thing, so it was probably not the food. The problem went away when I was back in the valley the next day. I came up with the theory that the lower air pressure at the higher elevation caused our bodies to expel gas in order to balance internal and external pressure. Could this be, or should I dump this farting woman?

Cecil replies:

Excuse me? You think your own toots smell like lilacs in May? But you're on the right track with this pressure thing.

Medical researchers have a pretty sorry record when it comes to answering the vital questions of life, but by God when it comes to flatulence they are on the case. In 1967 the New York Academy of Sciences devoted a two-day conference to gastrointestinal gas.

The gas issue was hot then because of the space program. Many feared man's mission to the stars might come to grief if an astronaut had a little too much chili before liftoff and the crew was, you know, overcome.

One of many fascinating nuggets brought to light during the conference was the effect of altitude on gas. During World War II flight surgeons had discovered that above 30,000 feet some aviators suffered pain from abdominal distension due to expansion of intestinal gas. What happened was that as outside air pressure decreased, the volume occupied by intestinal gas increased.

Experiments revealed that the volume of gas, typically around 115 milliliters at sea level, doubled at 15,000 feet, tripled at 25,000 feet, and rose by a factor of 7.6 at 40,000 feet. The increase from your 6,000-foot climb was less dramatic but probably enough to make your gut puff up like a balloon. Be grateful all you did was fart.

Full of it

Dear Cecil:

As one of your faithful but know-it-all-too-just-not-as-witty-by-half readers, I have a comment on your column about increased flatulence at high altitude. Atmospheric pressure drops to half that at mean sea level at about 18,000 feet, so trapped gases double in volume. Having flown thousands of flights in unpressurized planes and in altitude chambers, experience tells my nose when we go over about 25,000 feet. Good check for oxygen mask fit. Your reader, however, was suffering from transverse incarcerated farts at 9,000 feet. That's about 72 percent of sea-level pressure, and thus gas expands by about 39 percent — a small diameter increase. I suspect Bacchus and Eros affected this fellow much more than Charles' Law.

Cecil replies:

Booze plus lust is a major cause of flatulence? Remind me never to accompany you to a singles bar.

It may be true that when strapped into a cockpit you don't get noticeable liberation of gas until above 25,000 feet. However, when you have sex you move around, or at least most people move around, thereby increasing opportunities for gas to escape. So it seems reasonable intestinal distension at 9,000 feet might lead to an attack of the toots. Luckily we don't need to depend entirely on speculation. See below.

Dear Cecil:

[Flatulence] is a well-known phenomenon among skydivers. Crowded into a tight aircraft, as you pass between 6,000 and 8,000 feet, there is a good chance someone will let rip. We just consider it a recreational hazard.

Cecil replies:

Skydiving being what it is, Cecil cheerfully admits that increased flatulence may be partly due to your being in a state of generalized muscular tension. But isn't that pretty much what happens during sex?

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