This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: What does a clean room smell like? Many people say citrus, pine, or flowers because these fragrances are common in cleaning products.
A research team led by Brandon Boor found that scent compounds in cleaning products—conventional and botanical essential oil-based—quickly react in the air, forming nanoparticles that can travel deep into the lungs if inhaled. To reduce exposure to this invisible pollution, the team suggests using unscented products, running exhaust fans, and avoiding ozone-generating devices while cleaning. The researchers will present their results at the fall meeting of the American Chemical Society (ACS) during the "Healthy Indoor Spaces: Bridging the Microbiome and Chemistry" symposium at McCormick Place.
ACS Fall 2026 is being held Aug. 23–27. "We showed that indoor ozone reactions with fragrances from cleaning produce nanoparticles that carry a respiratory dose comparable to or greater than what you would experience from standing outside along a busy road," says Boor, an assistant professor of civil and construction engineering at Purdue University who studies indoor air quality. "The particles are different in terms of their composition, but the total dose can be higher.
You're not seeing smoke, dust or haze in the air. Instead, you think the air smells great, so it must be clean." Boor and his colleague Nusrat Jung, a Purdue assistant professor of civil and construction engineering, started studying the impact of cleaning products and chemical disinfectants on indoor environments during the COVID-19 pandemic. In that work, they observed that many of these products are heavily scented.
"That's often to create a pleasant smellscape in the indoor space," says Boor. "But clean air should not smell like highly concentrated citrus fruit. It should not really smell of anything." Atmospheric chemists previously established that terpenes emitted by plants, such as pinene from pine trees, react with ozone to create airborne nanoparticles.
The nanoparticles aggregate and eventually grow large enough to seed clouds. But in forests, terpene levels are relatively low, so particle formation occurs slowly. Using scented products indoors releases terpenes as the fragrance compounds evaporate from surfaces or spray droplets.
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