Key Takeaways
Air in hospitals and airplane cabins is generally free of disease-causing germs, study says
Most microbes found were harmless ones associated with human skin
Researchers analyzed the outside of face masks and an airplane filter
FRIDAY, Dec. 5, 2025 (HealthDay News) — Germophobes can breathe a little easier when visiting a hospital or taking an airplane trip, a new study says.
The ambient air on planes and in hospitals mostly contains harmless microbes typically associated with human skin, researchers reported Dec. 4 in the journal Microbiome.
The cutting-edge study analyzed germ samples captured on the outer surface of face masks worn by air travelers and health care workers, researchers said.
“We realized that we could use face masks as a cheap, easy air-sampling device for personal exposures and general exposures,” senior researcher Erica Hartmann, an associate professor of civil and environmental engineering at Northwestern University in Evanston, Illinois, said in a news release.
“We extracted DNA from those masks and examined the types of bacteria found there,” Hartmann said.
Overall, the team analyzed germs drawn from masks worn by 10 air travelers and 12 health care professionals. Travelers turned in their masks following a flight, hospital workers following a shift.
Researchers also analyzed germs captured by an aircraft cabin filter that had been used for more than 8,000 hours.
Overall, the team found 407 distinct species of microbes.
“Somewhat unsurprisingly, the bacteria were the types that we would typically associate with indoor air,” Hartmann said. “Indoor air looks like indoor air, which also looks like human skin.”
A few potentially disease-causing germs did show up, but they were in extremely low amounts and without signs of active infection, researchers said.
Hartmann’s team came up with the study idea in January 2022, amid the COVID pandemic.
“At the time, there was a serious concern about COVID transmission on planes,” Hartmann said. “HEPA filters on planes filter the air with incredibly high efficiency, so we thought it would be a great way to capture everything in the air.”
“But these filters are not like the filters in our cars or homes,” Hartmann added. “They cost thousands of dollars and, in order to remove them, workers have to pull the airplane out of service for maintenance. This obviously costs an incredible amount of money, and that was eye opening.”
To beef up their project, the team turned to a much cheaper alternative: face masks.
They also decided to include hospitals as another study locale.
“As a comparison group, we thought about another population of people who were likely wearing masks anyway,” Hartmann said. “We landed on health care providers.”
The results indicate that people themselves are the main source of airborne microbes in enclosed settings, and that most of the germs come from people’s skin rather than from any illnesses, researchers said.
Although the results show indoor air is relatively safe, researchers noted that infectious germs also spread through other routes — most importantly, touch.
“For this study, we solely looked at what’s in the air,” Hartmann said. “Hand hygiene remains an effective way to prevent diseases transmission from surfaces. We were interested in what people are exposed to via air, even if they are washing their hands.”
More information
The American Lung Association has more on infectious lung diseases.
SOURCES: Northwestern University, news release, Dec. 3, 2025; Microbiome, Dec. 4, 2025
What This Means For You
Ambient air in closed environments like an airplane cabin is relatively free of harmful germs, researchers say.
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