Scientists get smart about farts with new underwear sensor

Everybody farts. The question is, how often? And how much gas is too much gas to pass? Science is now starting to answer that question. All it took was inventing a special device to fit into underpants.

Until now, no one has measured flatulence in people’s daily lives.

Brantley Hall is a microbiologist and part of a team that studies the metabolism of gut microbes. Working at the University of Maryland in College Park, the group was measuring how much hydrogen gut microbes make. They used a sensor in an oxygen-free chamber. But they weren’t getting results.

Frustrated, “we took the sensor out of the chamber, and we were like, ‘Screw it. We’re going to try to measure a fart.’” So, Hall stuck the device down his own pants and let rip. “And the signal was enormous!”

Inspired by that incident, his team devised what they’re calling “smart underwear.” Its sensor tracks toots, specifically the hydrogen part of farts. This hydrogen tracker is about as big as a quarter and snaps onto regular underwear.

The researchers described their innovation in the December 2025 Biosensors and Bioelectronics: X.

Tootin’ time

Healthy college-age volunteers tested the device. People averaged 32 farts a day, the new sensors showed. But there was a wide range of results. Some people may toot as few as four times a day. Others passed gas as often as 59 times a day. Thirty-eight volunteers ate high-fiber gumdrops during the tests. Among them, the data show, all but two broke wind more often than they did on days when they didn’t eat these gumdrops.

Hall now wants to expand the study to a much larger and more diverse group. He wants to find out whether age, diet or other things affect our gassiness.

Hall says his group was “shocked by the lack of measurements of intestinal gas.” Health workers know what’s normal for other vitals, such as heart rate, he points out. “But if you go to the doctor, they don’t know the normal number of farts,” Hall says. “If you tell them, ‘I’m farting 50 times a day,’ they don’t have really a baseline to compare that to.”

For instance, no one knows how much people fart at night. In medical settings, most studies have used rectal tubes. Other studies asked people to record their own farts — which they can’t do while asleep. “Basically, because of the limitations of measuring farts, [there is a] complete gap in our understanding,” he says. “We just genuinely don’t know. Isn’t that funny? [In] 2026, we don’t know if people are farting at night or not.”

The Human Flatus Atlas

In February, Hall’s team launched a project that builds on their first study. They hope it will identify a normal fart range. They’re calling this project the Human Flatus Atlas. (Flatus is a fancy word for fart.) Volunteers must wear the sensors in their underwear around the clock. (That’s except for a 15-minute charge time while they shower.) They will do this for between three and 30 days. They must photograph what they eat using an app on their phones.

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Once they’ve located the right spot to attach it, most people don’t even feel the device, Hall says. They can wear it for almost all activities. “We’ve had people play rugby, run a 5K, do hours of volleyball practice — no problem,” Hall says. The one exception: “Biking is out. No biking.” The reason? Bike seats hit right where the sensors attach.

In the pilot study, few people found the device too uncomfortable to take part. They were more likely to lose the device or wash it.

Findings from that study suggest people tend to fall into three main categories. Remember that playground rhyme: “Beans, beans, the musical fruit, the more you eat, the more you toot?” Well for one group, it does not hold. These “zen digesters” rarely fart even after eating lots of fiber. At the other end of the spectrum are “hydrogen hyperproducers.” They fart a lot.

In between are what Hall’s group is calling “normal people” (though these researchers admit they still don’t yet know the true normal range). The most and least prolific tooters in the Atlas project will get 3-D-printed plaques marking their flatus status.

Like the cheese-cutting that started it all, interest in the Atlas has been huge. The initial batch of 800 sensors flew out the door in just a few days. More than 3,500 people expressed interest. Enrollment is currently paused while the researchers make more devices. But the project may soon open to accept people on the waiting list. Perhaps others may join in the future.

Hall’s team also launched a startup company called Ventoscity. They want to help companies that make fiber products sniff out how much flatulence is caused by their items.

Excitement for the Atlas project surprised Hall. Stigma and taboos discourage discussing bodily functions. “But almost people want to talk too much to me about it,” he says. “People are very excited about measuring farts.”