Study Shows Portable Air Cleaners Initially Elevate Transmission of Respiratory Disease

A new study published in Indoor Air found portable air cleaners may elevate the short-term risk of respiratory disease transmission due to increased air mixing. However, the long-term benefits of enhanced ventilation outweighed the initial increase in risk, reducing overall airborne transmission over extended durations.

The researchers said the work is important in demonstrating how rapidly respiratory airborne particles spread in ventilated spaces and what effect a partition wall has on the delay of concentration rise. It took between 15 and 100 seconds for contaminants emitted by a human simulator to reach the exposed simulator′s breathing zone in the mixing-ventilated test room, depending on the obstacles along the airflow path. The shortest delay occurred between standing and sitting dummies, while the longest delay was observed between dummies seated at desks separated by a partition wall. 

The study found that actions to enhance ventilation, such as increasing ventilation airflow rates or using portable air cleaners, can reduce occupants′ exposure to airborne pathogens and thus infection transmission risk. Conversely, additional air cleaners in the room may enhance air mixing and reduce delays, allowing contaminants to reach the exposed person′s breathing zone more quickly. This could lead to slightly higher initial concentrations during short-term exposures with air cleaners compared to without them, researchers said. However, within just a few minutes, researchers found that airborne exposures became significantly lower and remained so with the use of air cleaners.

The researchers said the results were limited due to small rooms with mixing-type ventilation, and that further studies are needed to investigate transmission in larger spaces ventilated by different methods.