AIR CLEANERS AND FILTERS IN SCHOOLS
WHAT ARE AIR CLEANERS AND WHAT ARE HEPA FILTER UNITS?
Air cleaners are devices that can be installed in classrooms, and other rooms within a school, to reduce exposure to particles, microorganisms and other small substances that may be floating in the air. Air cleaners can use different technologies like air filters or ultraviolet light. In classrooms, HEPA filter units are the most commonly used air cleaner devices. HEPA filter units use a fan to draw air through a very fine filter (a high-efficiency particulate air filter, or 'HEPA filter') to remove particles from the air. These devices can improve air quality but they can't replace ventilation because they don't provide fresh air.
WHEN MIGHT THESE DEVICES BE NEEDED?
Air cleaners are most useful when the ventilation in a school is not sufficient and can't easily be improved. The ventilation is not sufficient when the flow of fresh air from outdoors is inadequate for the number of people inside. This may be because the designed ventilation provision is compromised (for example by the presence of outdoor air pollution or noise, the weather, or security issues, limiting the ventilation) or because the usage of the room, or the needs of those within, has changed over time.
HOW DO WE KNOW HEPA FILTER UNITS WORK?
There are many studies carried out in laboratories and in real-world buildings (including in schools) that show that air cleaners can reduce the exposure to both particles and microorganisms in air. The evidence is summarised in this report written by the PROTECT COVID-19 National Core Study and this paper prepared by the SAGE Environmental Modelling group.
WANT TO FIND OUT MORE?
Here are three videos to help you understand more:
Are you interested to learn more about the topic in general? Watch our 'Air cleaners in schools' video.
Are you a classroom user and do you want to know more about how to use HEPA filter units? Watch our 'Using HEPA filter units in schools' video.
Are you part of a school leadership team and do you want to learn how to choose, install or maintain HEPA filter units? Watch our 'Choosing, installing and maintaining HEPA filter units' video.
NEED TO KNOW
Here are some additional facts
HEPA filter units use a very fine filter to remove particles from the air.
HEPA filter units can reduce exposure to air pollution and viral particles.
Air cleaners cannot replace adequate ventilation.
OTHER USEFUL RESOURCES INCLUDE:
The Department for Education's guidance on using air cleaning units in education and care settings, including a 'How to' guide, this 10-step guide to using air cleaning units in schools, and this TAPAS network position paper. It is possible to build DIY air cleaners known as 'Corsi-Rosenthal' boxes; these are constructed from a simple box fan, four filters, some cardboard and tape; they can make a great science project and more information is given in this Cambridge Mathematics blog post. This presentation from the COVID Pledge UK also describes how to build your box in the UK and this video shows the building process.