Since Covid-19 emerged over two years ago, scientists and researchers are continually building up a clearer picture about how the virus works, and how it transmits from one person to another.
What we’ve learned so far is that the virus is transmitted through a number of ways. Firstly, through direct or indirect contact, such as touching a surface or an object with the virus present, and then transferring it to your mouth, eyes or nose.
Secondly, Covid-19 can also be passed from one person to the next through inhaling infected respiratory droplets from an infected person, such as when they cough, sneeze, breathe or talk.
Taking into account Covid’s ability to spread through aerosol transmission, this has raised the question of whether air purifiers can help to protect against infection? Here’s everything you need to know about this pertinent topic.
How air purifiers work
In order to understand how effective, if at all, air purifiers are at combating the spread of Covid-19, it’s essential to get a clear understanding of how they actually work.
For starters, it’s worth noting that not all air purifiers are the same. Essentially, there are two types of air purifiers – those that filter air and those that sanitise it.
Filters work by removing very small particles from the atmosphere, such as pollen and dust, to help improve the quality of the air. HEPA (high-efficiency particulate arresting) filters are the most popular type, and can trap particles as tiny as .01 micron in diameter. These kind of filters are especially helpful for those who suffer from allergy conditions like hay fever.
Sanitisers work in a different way to filters in that they don’t remove particles from the atmosphere, but, instead, kill substances that could potentially make you ill or lower the air quality, such as mould spores, viruses and bacteria. The most popular type of sanitisers are those that use UV light to kill harmful substances.
Other types of air purifiers also exist, including ionizers and ozone generators, but filters and sanitisers are the most popular options used in domestic, public and commercial settings. Some purifiers combine both filters and sanitisers in the same unit.
Can an air purifier protect against Covid-19?
When it comes to assessing whether an air purifier is effective at protecting against Covid-19 transmission, the answer isn’t black or white. There are a number of factors you need to take into account, such as considering the type of air purifier you choose.
Early research indicates that some air purifiers, such as filters, can make a difference to reduce the levels of coronavirus in the atmosphere, especially if the system is switched on for a significant period of time. It’s also thought that Covid-19 particles can be killed by exposure to UV light, so purifiers using UV systems may be able to help reduce airborne transmission.
What is also important to consider is the type of HEPA filter used. SARS-CoV-2, the virus that leads to Covid-19, consists of particles that are a miniscule 0.125 micron in size. So, using a filter that is able to trap particles of this size is key.
Medical grade filters used in air purifiers in hospital settings, such as HEPA 14 filters, are effective at eliminating many airborne particles, including most traces of Covid-19. This is especially the case when used in conjunction with UV sterilisers.
But, even outside of hospital settings, air purifiers can have a part to play in reducing the spread of Covid-19. In particular, those air purifiers with filters that can capture particles within the range of 0.01 microns or larger may have an efficiency rating of up to 99.95%, especially when combined with a UV lamp.
Additionally, a US study conducted in 2021 found that portable HEPA air purifiers reduced exposure to the Covid-19 virus particles. Although this research took place in conference rooms rather than in domestic environments, it does show that HEPA filters can make a positive contribution to reducing virus transmission.
However, it’s worth noting that research is still ongoing and there is still a lot to learn about how the virus works, and how, and to what extent, air purifiers can be used to combat transmission.
Experts are keen to stress that air purifiers are only part of the solution and should be considered alongside other measures to help prevent the spread of Covid.
For instance, air purifiers only work against aerosol transmission; they won’t stop you catching Covid from direct or indirect contact with an infected surface or object. Regularly washing or sanitising your hands is, therefore, still recommended, even in spaces where air purifiers are present.
Additionally, air purifiers seem to work best for long-range transmission of airborne droplets, which are those particles that linger in the air, such as after a person has left a room. This is because particles tend to be smaller than those exposed in droplets immediately after someone coughs or sneezes, for example.
Therefore, to reduce your risk of spreading the virus or becoming infected, social distancing and wearing masks are still recommended measures, especially in busy or crowded spaces. Ventilation is also effective at dispersing Covid droplets, so opening windows and doors can help.
Should you get an air purifier?
If you’re thinking about getting an air purifier as part of your armoury to protect against Covid-19, there are a few considerations you should make.
Air purifiers may be more beneficial for spaces that have a lot of people coming or going, so if you live alone, getting one probably won’t be necessary if protecting against Covid-19 is your main concern. That said, air purifiers can help to improve air quality and reduce allergens, so they’re beneficial in more ways than one.
When looking for an air purifier, think about where you’ll place it. The smaller the room, the more effective a purifier will be – and make sure to always keep the doors closed. If you have a large floor area with high ceilings, it might be worth getting two units. If someone in your household has tested positive or is isolating, then place the air purifier in that room and keep the doors closed, to protect any caregivers or other household members from becoming infected.
Do your research before buying an air purifier and look for a good quality model that doesn’t make any false advertising claims. Some come with a range of useful features such as allowing you to control the unit through your smartphone or have automatic settings, which turn the machine on when air contaminants rise.
If you choose a filter unit, look for a recommended HEPA model which is able to filter particles within the 0.1-1 size range.
Make sure to change the filter regularly, according to the manufacturer’s instructions. However, the more you use the air purifier, the sooner a filter might need replacing, or the UV light might fade, so get into the habit of frequently checking the condition of the unit to ensure it’s in good working order.
With the right type of air purifier, in the right setting and circumstances, this, combined with practicing other measures, can be another useful weapon in the fight to protect against Covid-19 infection and transmission.