Research Reveals Insufficient Evidence Supporting Air-Cleaning Technologies for Respiratory Infection Prevention

A comprehensive analysis conducted by researchers from the University of Colorado Anschutz Medical Campus and the National Institute for Occupational Safety and Health (NIOSH), part of the CDC, has highlighted significant gaps in the scientific evidence backing the effectiveness of various indoor air-cleaning technologies aimed at reducing respiratory infections such as COVID-19 and the flu. Despite the widespread use of devices like HEPA filters, UV light sterilizers, ionizers, and advanced ventilation systems in homes, schools, and public buildings, most of these interventions have not been rigorously tested in real-world settings involving human exposure.

The study, published in the Annals of Internal Medicine, reviewed nearly 700 studies spanning nearly a century, from 1929 to 2024, focusing on engineering controls designed to improve indoor air quality. It found that only about 9% of these studies assessed actual health outcomes like infection rates among people, with the majority relying on indirect metrics such as particle counts, tracer gases, or microbial proxies. This raises questions about whether these technologies truly decrease illness, as evidence from real-world scenarios remains limited.

Lead researcher Dr. Lisa Bero emphasized the disconnect between laboratory tests and practical applications, stating, "Most research has been conducted in controlled lab environments rather than where people live and work. We need better studies that measure actual health impacts, including whether these devices reduce infections and improve wellbeing."

Furthermore, the review highlighted safety concerns with some air-cleaning devices, especially those that produce ozone, a potentially harmful chemical known to irritate lungs and worsen respiratory conditions. Despite this, few studies have thoroughly examined the long-term safety of these technologies, particularly their emissions and potential side effects.

Experts warn that while the promise of these devices appears compelling, current evidence does not unequivocally confirm their effectiveness. Dr. Amiran Baduashvili noted, "Many devices look promising but we lack definitive proof that they work outside the lab. Consumers and institutions should be cautious and favor interventions with verified safety and efficacy."

The researchers advocate for new, well-designed studies that evaluate respiratory infection rates in real-world settings, considering not just particle reduction but also potential adverse health effects, environmental impacts, cost, and accessibility. They call for establishing standardized health outcomes to improve comparability across studies and to better inform public health policies.

In the meantime, experts recommend relying on fundamental practices such as enhancing ventilation, opening windows, and maintaining cleanliness, which are proven to promote healthier indoor environments. Consumers are advised to choose independently tested products, avoid those that emit harmful byproducts like ozone, and stay informed about the safety and efficacy of air-cleaning technologies.

"This analysis underscores the urgent need for rigorous scientific research to guide safer, more effective strategies for indoor air quality management, especially as respiratory infections continue to pose a major public health challenge," concluded Dr. Bero.

source: https://medicalxpress.com/news/2025-08-gaps-evidence-air-technologies-respiratory.html