Air cleaning technology claims to reduce the transmission of infectious microbes in indoor settings. In the review, researchers looked at 672 studies published between 1929 and 2024 that analyzed equipment used for this purpose.
A prominent concern was that out of the 672 studies, only 57 (less than 9 percent) involved human participants.
Another contentious issue was that most studies measured things such as dust particles or harmless microbes rather than illness-causing bacteria and viruses, it states.
“We were surprised to find that most of the research tested air cleaning devices in lab chambers, not in real-world settings where people live, work or go to school,” said Lisa Bero, professor of internal medicine at the University of Colorado School of Medicine and co-author of the paper.
“We need stronger studies that look at actual health outcomes, whether people are actually exposed to fewer pathogens or get sick less often, and not just measurements of particles in the air.”
Amiran Baduashvili, the paper’s first author, said many of the indoor clean air technologies look promising on paper.
“[However,] we just don’t know if they work in the real world,” he said. “People are buying and installing these systems in homes and schools hoping to protect themselves and their families but the science hasn’t caught up to the marketing.”
The review also found that only a few studies measured the potential harms of using indoor air cleaning equipment.
What to Watch Out for
Bero suggested looking at whether manufacturers of indoor air cleaning devices provide adequate data on potentially harmful emissions during usage and guidelines on how to minimize them.“Being more aware of possible risks is an important part of making informed decisions especially as more people and organizations spend money on these technologies and bring them into clinics, schools and homes,” she said.
Researchers recommended choosing products that have been independently tested in real-world settings and avoiding devices that generate harmful byproducts such as ozone.
The review was funded by the Centers for Disease Control and Prevention’s (CDC’s) National Institute for Occupational Safety and Health (NIOSH). Seven authors reported they were employed by NIOSH/CDC, which also reviewed and approved the manuscript.
Another disturbing factor brought forth by the latest review was regarding the funding of such studies.
“Some of these studies are funded by the companies that make the technologies being evaluated, which creates a conflict of interest,” Bero said. “Until we do know more, the public deserves clear and transparent information.”
The technologies are not necessarily ineffective, Bero clarified.
“We’re saying we don’t know enough yet,” she said.
This includes controlling moisture, such as humidity and water leaks, cleaning up any visible mold, and drying up wet areas as quickly as possible.
“Regularly clean surfaces, including floors, walls, fixtures, and furnishings. For most routine cleaning of hard surfaces, damp wiping with clean water or water and a detergent is sufficient,” the EPA stated.
“Ventilation, such as opening windows to bring in outdoor air, can help to lower the concentrations of indoor air pollutants in your home.”
According to the agency, airborne viral particles spread more readily among people in indoor environments rather than outdoors.
The concentration of such particles tends to be higher indoors, the CDC stated.
“Protective indoor ventilation practices can reduce the airborne viral concentrations and the overall viral exposure to occupants,” the agency stated.
