We’re getting to grips with air purifier myths and revealing the science behind how effective these appliances really are. Claiming to clean the air in our homes, air purifiers have long been popular among consumers seeking to reduce their exposure to airborne pollutants commonly found in domestic settings, such as dust and pollen.

The importance of maintaining good indoor air quality has made global news headlines in recent months, with people seeking to mitigate the risk of COVID-19 aerosols entering their homes. And it’s not only the pandemic that’s behind the current popularity of the best air purifiers, the outbreak of wildfires across several continents, and increased levels of traffic pollution in major cities around the world have prompted many people to look for ways to reduce their exposure to smoke particles, carbon and other pollutants.

However, purchasing an air purifier isn’t a cure-all solution. We interrogate some of the claims made by manufacturers and explore the truth behind the promises. With these common air purifier myths debunked, you’ll better understand how these home appliances might benefit you and your family. And if you need to know more, take a look at our investigation into how air purifiers work.

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Types of Air Purifiers

Before we get into the myths that surround air purifiers, it's worth establishing the different types of features available within air purifiers:

HEPA filter: an air purifier with a HEPA filter will remove more particles from the air compared to one without a HEPA filter. However, look out for terms such HEPA-type, or HEPA-style, as there’s no guarantee that this will conform to industry regulations. And if you're wondering if HEPA filters can remove viruses... the answer is no (at least, not completely).

Carbon filter: an air purifier with a carbon filter will also capture gases and volatile organic compounds (VOCs) that are released from common household cleaning products and paints.

Sensors: an air purifier with an air-quality sensor will activate when they detect pollutants in the air, and will often provide information about the quality of the air in the room it’s situated in. In addition, a smart air purifier (that’s connected to the internet) will send detailed reports directly to your smartphone, so you can easily monitor your indoor air quality.

Air purifier myths debunked

Air purifier myths: They’ll improve your health

Air purifiers work by filtering some pollutant particles out of the air, which means asthma and allergy sufferers might benefit from using one. According to the British Lung Foundation, if you have a confirmed pet allergy you can use an air purifier to reduce airborne pet allergens – in these instances, a purifier fitted with a High-Efficiency Particulate Air filter (HEPA filter) is recommended.

However, it will only be effective at managing the causes and reducing symptoms if it’s capable of capturing the allergens that trigger a reaction. And, as Dr. John O Warner OBE – Emeritus Professor of Paediatrics, National Heart and Lung Institute, Imperial College London – told Live Science, dust mites or pet dander are not able to be captured when embedded in furniture or carpets.

So while the claim that air purifiers will improve your health is not technically a myth, it really depends on finding a system that works for the individual. It’s also important to check that the air purifier is ozone-free before making a purchase, as some emit low levels of ozone that can actually make asthma symptoms worse, according to Asthma UK. As always, if you are experiencing health issues or are unsure as to the best way to manage a diagnosed medical condition, it’s important to seek medical advice.

Air purifier myths: If you have an air conditioner, you don’t need a purifier

We can ensure this air purifier myth is debunked quickly because – put simply – this statement simply isn’t true. While air conditioner systems are often equipped with some basic filtration functions, they are not able to filter out the microscopic particles that a HEPA filter can capture. An air conditioner's primary function is to regulate the air temperature within a room, and is not designed to trap airborne pollutants. It is possible, however, to use an air conditioner and an air purifier simultaneously to achieve both of these objectives.

Air purifier myths: Air purifiers need a HEPA filter to work

Most air purifiers consist of a filter, or multiple filters, and a fan that draws in and circulates air. As air travels through the filter, particles are captured and the clean air is pushed back out into the living space.

An air purifier will remove some particles from the air, however, one that’s fitted with a HEPA filter – that consists of multiple layers of netting or mesh, most often made from interwoven glass fibers or synthetic materials – will be able to remove more particles from the air. “A HEPA filter will filter particles down to 0.3 of a micron, and that's 99.9% of all particles down to 0.3 of a micron, which includes pollen grains, house mites and pet allergens, all of which are slightly larger than that," said Dr Warner. “However, an air purifier will only filter out these particles within the zone created by the system. And with most purifiers, the zone is almost non-existent."

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Air purifier myths: Air purifiers will protect you against COVID-19

The ability of air purifiers to combat the spread of COVID-19 particles has been widely discussed in recent months, and a £1.8m study backed by the Department for Health and Social Care is currently taking place across 30 UK primary schools to assess the effectiveness of air-cleaning systems at eliminating the virus.

So, is this an air purifier myth that needs to be debunked? “Viruses are below the limits set by HEPA filters," added Dr. Warner. “However, viruses are usually in aerosol, so an air filter might be able to trap viruses where the aerosol has evaporated off, which could have some benefit. It will, however, deal with bacteria, which are mostly about 0.3 microns."

Until more conclusive scientific evidence is released, Dr. Warner recommends the best approach is to ensure indoor spaces are well ventilated. “Allowing the airflow to take particles away by having a door or a window open is often better than having an air purifier," he said.