Healthy adults pass gas an average of 32 times a day. The figure most often repeated in medical literature is 14, give or take six.
That gap comes from a small electronic device that snaps onto ordinary underwear and counts hydrogen releases around the clock. University of Maryland researchers call it Smart Underwear, and they describe it as the first wearable built specifically to measure human flatulence.
The joke writes itself. The underlying problem is not funny to anyone who has sat in a gastroenterologist's office complaining of excessive gas and been told there is no way to check.
The Measurement Problem Behind the Punchline
Gastroenterologist Michael Levitt, known in the field as the King of Farts for his career studying intestinal gas, laid out the difficulty in 2000. He wrote that it is virtually impossible for a physician to objectively document excessive gas using available tests.
A quarter century later, that had not changed much. Earlier flatulence research relied on invasive techniques in small groups of volunteers, or on self-reporting, which misses events, depends on memory and cannot capture anything that happens during sleep.
Brantley Hall, an assistant professor in the Department of Cell Biology and Molecular Genetics at Maryland, led the team that built an alternative. The device uses electrochemical sensors to track intestinal gas production continuously, day and night, without anyone needing to notice or remember.
The findings appeared in Biosensors and Bioelectronics: X, with assistant research scientist Santiago Botasini as first author.
Hydrogen Is the Signal, and Microbes Are the Source
The sensor does not count farts directly. It counts hydrogen.
In most people, flatus consists mainly of hydrogen, carbon dioxide and nitrogen, with some individuals also producing methane. Hydrogen matters because human cells do not make it. It comes exclusively from gut microbes fermenting dietary material, which means a continuous hydrogen readout is a continuous readout of microbial activity.
"Think of it like a continuous glucose monitor, but for intestinal gas," Hall said in a university announcement, noting that the device detected the rise in hydrogen following consumption of the prebiotic fiber inulin with 94.7% sensitivity.
That is the part with real clinical potential. Researchers have spent two decades cataloguing which bacteria live in the human gut. Watching what those bacteria are doing hour by hour, in someone going about a normal day, has been much harder.
The variation the team found was extreme. Daily totals across the study ranged from four flatus events to 59.
Visceral sensitivity complicates the picture further. Two people can produce nearly identical volumes of gas and experience them completely differently, which is part of why patient complaints and objective output have never lined up neatly.
Zen Digesters, Hyperproducers and a National Recruitment Drive
Normal ranges exist for blood glucose, cholesterol and dozens of other measures. None exists for this one.
"We don't actually know what normal flatus production looks like," Hall said. "Without that baseline, it's hard to know when someone's gas production is truly excessive."
The Hall Lab is now running the Human Flatus Atlas, a nationwide project to establish that baseline. Devices ship directly to participants, so adults 18 and older anywhere in the United States can enroll remotely. The registered protocol asks participants to wear the device at least 12 hours a day for three consecutive days and to log every meal with photos through a smartphone app.
Recruitment is organized around three categories drawn from the early work.
Zen Digesters eat 25 to 38 grams of fiber daily yet produce minimal gas. Hydrogen Hyperproducers are, in the team's phrasing, people who fart a lot. Normal People fall in between. Stool samples from the two extremes will go for microbiome analysis, on the theory that whatever separates them is worth identifying.
The Serious Work Is Already Underway
A second application has moved further than the fart counter framing suggests.
A trial sponsored by the University of Colorado Denver, funded through the National Institute of Diabetes and Digestive and Kidney Diseases, is using a Smart Underwear prototype to measure diet-driven changes in gut microbial hydrogen sulfide production. That study feeds participants high-cysteine and low-cysteine diets in a crossover design, with six-day diet periods separated by a washout of about 11 days.
Hydrogen sulfide is not a punchline. Excessive gut microbial production of it has been linked in several lines of evidence to conditions including colorectal cancer, and the trial documentation notes that existing measurement techniques are imprecise and invasive.
Two caveats belong on the record. As Scientific American reported, the 32-per-day figure comes from 19 healthy adults who wore the device for a week while awake, which is a small sample for a population claim, and the Atlas is designed precisely to widen it. And Hall and Botasini have filed patent applications on the device and founded a company, Ventoscity, which has licensed the university technology. The research itself was supported by the University of Maryland, the Maryland Innovation Initiative and the UM Ventures Medical Device Development Fund.
None of this is available to buy, and nobody should read a gas count as a diagnosis. Persistent bloating, pain or changes in bowel habits are worth discussing with a clinician rather than a sensor.
Key Questions Answered
What is Smart Underwear? A small wearable device developed at the University of Maryland that snaps onto regular underwear and uses electrochemical sensors to track hydrogen in flatus continuously.
Why 32 instead of 14? Older estimates came from invasive techniques in small studies or from self-reporting, which misses events and cannot capture gas passed during sleep. Continuous sensing catches more.
Why measure hydrogen specifically? Human cells do not produce hydrogen. It comes only from gut microbes fermenting food, so hydrogen output is a direct readout of microbial activity.
Is a high number a medical problem? Not on its own. Individual totals ranged from four to 59 per day, and no established normal range exists yet. That is what the Human Flatus Atlas is trying to establish.
Can people buy this? No. It is a research device. Adults in the US can enroll in the Human Flatus Atlas study to receive one for the study period.
Does it have uses beyond counting? A federally funded trial is using a prototype to measure gut microbial hydrogen sulfide production, which has been linked to colorectal cancer and other conditions.
