Do air purifiers for schools really work?

Environmental technologies such as air purifiers offer a potential solution to minimising the spread of coronavirus and other respiratory illnesses in settings such as schools, hospitals, and workplaces.

However, concerns have been raised over the effectiveness of these products and whether they are fit for purpose.

In this article we explore how air purifiers for schools work and how to ensure you choose a unit that meets the appropriate standards for your requirements.

The government has announced plans to introduce air purifiers for schools

Why are air purifiers for schools being introduced?

In January, then Education Secretary Nadhim Zahawi announced additional measures designed to help make the return to schools safer for pupils and staff. This included providing a number of air purifiers to schools where quick fixes to improve ventilation (i.e. opening a window) were not possible.

7,000 new air purifiers were made available to these schools, while an additional 1,000 were announced for special schools and alternative provision settings. However, an increasing number of schools are now choosing to invest in air purification technology, in addition to NHS settings and workplaces.

Even without a pandemic to contend with, air filtration is more important than many of us realise and indoor air contains many different irritants and pollutants, including common household allergens such as pet dander, mould spores and dust particles, Removing these efficiently can vastly improve the quality of air we breathe. 

What is an air purifier?


Air purifiers are devices designed to remove contaminants from indoor air. It has been determined that indoor air quality can be up to seven times poorer than outdoors, while viruses and particles from sneezes and coughs can hang in indoor air for up to 45 minutes.

While they can be used to remove a number of pollutant types, for example odours, smoke, pollen and mould spores, at the moment the focus is on their effectiveness for removing particles containing viruses – most notably COVID-19.

What is a HEPA filter?

HEPA (high efficiency particulate air) filters are air filters which meet the HEPA standard (defined by EN 1822 and EN ISO 29463). Filters which comply to this standard must trap 99.97% of particulates 0.3 microns or larger. To put this into context, there are 10,000 microns in a single centimetre.

As with all air purification/filtration technology, it’s important to remember that the filter’s true effectiveness will depend on a range of external factors, such as the positioning of the device, whether it is being used correctly, and age of the filter.

The key benefit of a HEPA filter is that you can be confident the technology you have chosen has been tested and complies with a certain standard and when used correctly will remove almost 100% of the tiniest of airborne particles. 

The problem with HEPA filters as a tool for keeping schools covid-free, is that coronavirus particles are 0.1 – 0.5 microns – although this does not account for particles being carried in aerosols and respiratory droplets, which are much larger and can be captured. So while HEPA filters can be a highly effective tool and will almost certainly remove a significant amount of coronavirus particles, it would be wrong to install one in a classroom and assume it will keep it covid-free.

Ionic air purifiers

Ionic air purifiers improve air quality by emitting large amounts of electrically charged ions. The ions attach to particles and ground them to surfaces such as floors or walls. While this technique does work to improve air quality, as the particles haven’t actually been removed there is a risk that they will be recirculated once disturbed (for example through sweeping the floor or even leaning on a wall).

Ionic air purifiers tend to be a less expensive option than HEPA filters, however they may not be the best solution for a classroom environment. Research has also highlighted that the use of this type of purifier can also have a negative impact on health. This is because negative ions increase oxidative stress.

What’s the problem with relying on air purifiers?

The main issue with using air purifiers is that they are often not a complete solution. The use of air purifiers alone cannot ensure adequate indoor air quality, particularly where significant pollutant sources are present and ventilation is insufficient.

The unit must be a suitable size for the space it is being used in. Anyone can order an air purifier and place it in a classroom, but that doesn’t guarantee a significant improvement in air quality. Variables such as the location of the device, maintenance and room ventilation all have an impact.

In order for an air purifier to effectively remove viruses from the air, it needs to be able to remove very small airborne particles (typically in the 0.1-1 um range). Although HEPA filters are a good solution, they alone are not capable of actually killing airborne microbes and bacteria. Viruses such as coronavirus will still be present unless they are either destroyed or effectively removed. There is a similar issue with ionic air purifiers. Ultimately, neither type is fully effective for a classroom environment – a combined approach is required.

There have also been concerns over the lack of performance standards and regulation of air purifiers. At present, TÜV NORD is the only authority to establish a comprehensive test for these products.

How can you ensure you choose the right air purifiers for schools?

The best way to ensure the air purifying device you choose is fit for purpose is to consult a ventilation system design expert who will be able to recommend the most suitable equipment for your requirements and ensure it is installed in an appropriate location.

In most workplace, classroom and hospital settings a combined approach is likely to be the best option.

At FEG, we recommend Bomaksan BOA air filters, the first company to receive TÜV NORD certification for their commercial HEPA air purifier, BOA Air.

About BOA AIR air purifiers for schools
BOA AIR high capacity compact air cleaner devices are suitable for use in crowded and large interior spaces thanks to its high air flow capacity and high ACPH.

BOA AIR high capacity compact air cleaner devices are suitable for use in crowded and large interior spaces thanks to its high air flow capacity and high ACPH.

BOA AIR purifying devices use three different stages of filtration to clean the air:

  • G4 class pre-filter – captures coarse particles, increasing the working efficiency of the activated carbon filter and extending the life of the HEPA filter
  • Activated carbon filter – traps VOC (volatile organic compounds), formaldehyde and odours
  • H14 Class HEPA filter – captures and traps PM1 particles, viruses and bacteria with 99.99% efficiency. H14 Class is the highest tier of HEPA air filtration. Devices with H14 Class filters are considered medical grade
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