Harvard Study Finds That HEPA Air Purifiers Fail to Fully Protect Schoolchildren from Viruses
Nikhil Prasad Fact checked by:Thailand Medical News Team Oct 12, 2025 1 month, 2 weeks, 2 days, 58 minutes ago
Medical News: Viral Threats Still Linger in Classrooms
As schools reopen and viruses like influenza and RSV make their seasonal comeback, a new study by researchers from Brigham and Women’s Hospital and Mass General Brigham reveals that simply installing HEPA air purifiers in classrooms may not be enough to keep students safe from airborne respiratory viruses. The researchers found that even with these high-efficiency air filters in place, the air inside classrooms contained several viruses that can cause illness among children and teachers.
Harvard Study Finds That HEPA Air Purifiers Fail to Fully Protect Schoolchildren from Viruses
According to the study, air samples taken from over 200 classrooms across 39 public schools in the Northeastern United States contained an average of three types of respiratory viruses. Some classrooms had as many as thirteen different viruses present, including influenza and respiratory syncytial virus (RSV). This finding, highlighted in this
Medical News report, underscores that HEPA purifiers alone did not lower the total viral load in classrooms, suggesting the need for a more comprehensive approach to protecting children’s health.
The Study and Its Surprising Results
The research was part of the School Inner-City Asthma Intervention Study (SICAS-2), a large randomized clinical trial that ran between 2015 and 2020. The original study aimed to find out whether air purifiers could reduce asthma symptoms among children with respiratory conditions. Classrooms were randomly assigned either real HEPA purifiers or “sham” machines that looked identical but had no filters. In this follow-up analysis, researchers instead measured viral concentrations in the air.
Out of 532 air samples collected, 98.5% contained detectable levels of viruses. The most common was the rhinovirus, found in nearly 90% of classrooms. Despite using active HEPA purifiers, researchers observed no significant reduction in the overall viral burden. However, there was a modest 32.8% drop in the diversity of virus types detected—meaning fewer different kinds of viruses were found, though the total amount of viral material in the air remained high.
Humidity and Other Hidden Factors
Interestingly, the researchers also discovered a strong link between low humidity levels and higher viral exposure. In drier classroom environments, viruses remained airborne for longer periods. The team suggested that maintaining classroom humidity between 40% and 60% could be a simple yet effective measure to limit viral spread. In addition to humidity, factors such as poor ventilation and coarse particulate matter also played a role in allowing viruses to persist in the air despite filtration systems.
Dr. Peggy S. Lai, the lead author of the study, emphasized that “school-aged children and teachers face increased risks from respiratory viruses, which can impact their health, lead to missed school days, and cause difficulties for families.” She added that while HEPA purifiers a
re helpful for removing dust and fine particles, reducing viral exposure requires multiple environmental strategies, including better ventilation and humidity control.
A Call for Broader Solutions
The researchers concluded that relying solely on HEPA air purifiers may not provide the level of protection schools expect. Instead, they recommend a combination of solutions—enhanced ventilation, proper humidity management, and perhaps even smarter design of classroom airflow systems. The goal is to minimize the concentration of viruses in the air where children spend most of their day.
The study findings were published in the peer reviewed journal: JAMA Network Open, and highlight how future public health strategies for schools must go beyond air purifiers to include more holistic environmental control methods.
https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2839930
Ensuring cleaner indoor air could significantly reduce school absences, improve learning conditions, and prevent community-wide outbreaks during viral seasons.
For the latest on air-filters, keep on logging to Thailand
Medical News.
Read Also:
https://www.thailandmedical.news/articles/coronavirus
https://www.thailandmedical.news/articles/h5n1-avian-flu
https://www.thailandmedical.news/articles/influenza-or-flu
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