As the debate on the safe reopening of schools continues this week, we take a look at the results of a brand-new study on the positive effects of HEPA air purification in the classroom.
The team from Goethe University in Frankfurt examined the role of HEPA air filtration in classrooms, as a way to keep students and teachers safe.
"Atmospheric researchers from Goethe University have demonstrated that air purifiers with a class H13 filter (HEPA) can lower aerosol concentration in a classroom by 90 percent within 30 minutes. Because this significantly reduces the risk of airborne infection with SARS-CoV-2, the scientists recommend placing such air purifiers in classrooms."
Covid-19 travels through the air
It is becoming increasingly clear that the main method of transmission for Covid-19 is airborne. Tiny particles of the virus are aerosolized when an infected person coughs, sneezes or even talks. These aerosolized droplets have the ability to travel significant distances and can remain suspended in the air, even after the infected person has left the room.
The classroom is a high risk environment
A person with Covid-19 is most contagious three days before they show any symptoms. And as many as 1 in 3 people with the virus show no symptoms at all. The risk of these pre-symptomatic and asymptomatic individuals infecting others is extremely high. Particularly in a classroom environment, where large groups of people are confined to a small space for long periods of time.
HEPA reduces the number of particles by 90%
For the purposes of the German study, airborne particles were measured in two classrooms, with windows and doors closed. Two HEPA air purifiers were then installed in one of the classrooms. After just 30 minutes, particle levels were reduced by 90% in the classroom with HEPA air purifiers.
Using HEPA in classrooms reduces the risk of infection
To measure the extent to which this reduces the risk of infection from Covid-19, the team also calculated the number of viral particles dispersed into a room when a highly contagious person is present. According to their calculations, using a HEPA air purifier in the same classroom as an infectious person, will reduce the risk of an ‘inhaled dose’ by six.
HEPA air filtration has a major part to play
Covid-19 is still a relatively new virus, there is no doubt we still have much to learn. But the results of this latest study are clear. Using HEPA air filtration in classrooms and other indoor spaces, will help to lower the risk of contracting the virus.
We carry 3 of the leading brands of HEPA air purifications systems. You can trust Austin Air, Aeris and AirPura units to provide clean air at home or in the classroom.
Operating schools during COVID-19: CDC's Considerations
Consider ventilation system upgrades or improvements and other steps to increase the delivery of clean air and dilute potential contaminants in the school. Obtain consultation from experienced Heating, Ventilation and Air Conditioning (HVAC) professionals when considering changes to HVAC systems and equipment. Some of the recommendations below are based on the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) Guidance for Building Operations During the COVID-19 Pandemicexternal icon. Review additional ASHRAE guidelines for schools and universitiespdf iconexternal icon for further information on ventilation recommendations for different types of buildings and building readiness for occupancy. Not all steps are applicable for all scenarios.
Improvement steps may include some or all of the following activities:
- Increase outdoor air ventilation, using caution in highly polluted areas.
- When weather conditions allow, increase fresh outdoor air by opening windows and doors. Do not open windows and doors if doing so poses a safety or health risk (e.g., risk of falling, triggering asthma symptoms) to children using the facility.
- Use child-safe fans to increase the effectiveness of open windows. Position fans securely and carefully in or near windows so as not to induce potentially contaminated airflow directly from one person over another (strategic fan placement to help draw fresh air into the classroom from open windows or to blow air from the classroom out open windows).
- Decrease occupancy in areas where outdoor ventilation cannot be increased.
- Ensure ventilation systems operate properly and provide acceptable indoor air quality for the current occupancy level for each space.
- Increase total airflow supply to occupied spaces, when possible.
- Disable demand-controlled ventilation (DCV) controls that reduce air supply based on occupancy or temperature during occupied hours.
- Further open minimum outdoor air dampers to reduce or eliminate HVAC air recirculation. In mild weather, this will not affect thermal comfort or humidity. However, this may be difficult to do in cold, hot, or humid weather.
- Improve central air filtration:
- Inspect filter housing and racks to ensure appropriate filter fit and check for ways to minimize filter bypass
- Check filters to ensure they are within service life and appropriately installed.
- Consider running the HVAC system at maximum outside airflow for 2 hours before and after the school is occupied.
- Ensure restroom exhaust fans are functional and operating at full capacity when the school is occupied.
- Inspect and maintain local exhaust ventilation in areas such as restrooms, kitchens, cooking areas, etc.
- Use portable high-efficiency particulate air (HEPA) fan/filtration systems to help enhance air cleaning (especially in higher risk areas such as the nurse’s office).
- Generate clean-to-less-clean air movement by re-evaluating the positioning of supply and exhaust air diffusers and/or dampers (especially in higher risk areas such as the nurse’s office).
- Consider using ultraviolet germicidal irradiation (UVGI) as a supplement to help inactivate the virus that causes COVID-19, especially if options for increasing room ventilation are limited.
- Ventilation considerations are also important on school buses.
*Note: The ventilation intervention considerations listed above come with a range of initial costs and operating costs which, along with risk assessment parameters such as community incidence rates, facemask compliance expectations and classroom density, may affect considerations for which interventions are implemented. Acquisition cost estimates (per room) for the listed ventilation interventions range from $0.00 (opening a window; inspecting and maintain local exhaust ventilation; disabling DCV controls; or repositioning outdoor air dampers) to <$100 (using fans to increase effectiveness of open windows; or repositioning supply/exhaust diffusers to create directional airflow) to approx. $500 (adding portable HEPA fan/filter systems) to approx. $1500 (adding upper room UVGI).