It’s no secret that classrooms can be superspreaders for germs and diseases. Now that most schools are fully in-person after a global pandemic, questions about the impact of indoor air quality on the safety of teachers and students — from COVID or otherwise — remain in the air.
In an effort to answer these concerns and prevent a similar catastrophe, a Harvard research team, led by Dr. Gen Pei with the Healthy Buildings Program, developed a new model to properly evaluate the effectiveness of portable air cleaners (PACs) in classrooms, and what factors can make a difference in mitigating disease. A Computational Fluid Dynamics (CFD) model showcasing its findings offers invaluable insights into airborne pathogen diffusion in education, and how PACs can step in to protect students and teachers from the spread of viruses.
Let’s look at the key takeaways.
Portable Air Cleaners Perform
This study echoes the results of other recent studies by showing Portable Air Clearers (PACs) reduce the spread of airborne diseases in classrooms. Dr. Gen Pei’s team, however, didn’t just see a slight decrease in aerosol intake (how much students breathed a mist representing pathogens in the study) — they recorded a mean reduction of 66% when PACs were used with a clean air flow rate of 2.6 air changes per hour (ACH). This means that even when an air cleaner has a relatively low ACH, the pathogens that students normally breathe from an infected person are cut down by two-thirds. This astonishing result becomes even more significant when considering the rest of the research findings.
Image: Harvard T.H. Chan’s Healthy Buildings Program developed Computational Fluid Dynamics (CFD) model evaluates the placement of portable air cleaners (PACs) in occupied classrooms.
Air Movement Is Crucial
By tracing the paths of aerosol concentrate in the classroom’s air, this study was able to pinpoint one of the key reasons PACs make a difference in cleaning the air of viruses: air movement. It might sound counterintuitive (given how similar “spread” and “mixing” can sound), but when PACs are used to mix the air at faster rates, classrooms can expel stale and infected air through exhaust vents faster. Not to mention, the movement helps prevent particles from immediately reaching students facing a speaker in the front row. With this discovery in mind, PACs prove especially needed by older school buildings with inadequate ventilation.
Placement Makes a Difference
The Harvard Health Buildings Program team certainly found that PACs will, overall, help with classroom air quality – but they also identified some key ways to make them as effective as possible. One highly influential factor: placement.
Obviously, the PAC is most effective when placed close to the infector. However, because students and teachers often either do not know that they are sick or choose to come to school anyway, it’s challenging to know the exact location of an infector. Therefore, the study suggests placement in the center of the room to most effectively mitigate transmission.
Adjusting Discharge Height Can Help
Similar to placement, the height at which the PAC mixes and discharges purified air can help make them even more effective. Based on their findings, the research team recommends adjustment of PAC flow discharge height to the breathing height of occupants. For reference, this is typically 0.9-1.2m (2.953 – 3.938 ft) for seated people.
A Proactive Approach to Classroom Air Quality
As discovered by Dr. Gen Pei, the Harvard Healthy Buildings Program and their insightful CFD model, PACs, when adequately placed and adjusted, are a valuable addition to classrooms looking to prevent the spread of infection. Whether the classroom is placed in a poorly ventilated building, or the school wants to improve how it protects the well-being of its staff and students, PACs reduce disease transmission by effectively purifying and moving the air.
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Read the full study here: https://pubs.rsc.org/en/content/articlelanding/2024/em/d4em00114a/
To learn more about Fellowes Air Quality Management solutions or to speak to a Fellowes IAQ expert for a complimentary IAQ assessment, click here: https://www.fellowes.com/us/en/catalog/air-quality-management/services/pg/indoor-air-quality-assessment
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