Air purifiers, effective or rip-off?

The air we breathe at home is often more polluted than the air outside, even in cities, according to the Indoor Air Quality Observatory. Do the air purifiers offered by many manufacturers really remedy this? And if so, which models to choose?

Between dust mites, mold spores and pollens responsible for allergies, tobacco smoke and formaldehyde classified as carcinogenic by the World Health Organization (WHO), organic solvents released by paints, glues and wood treated, carbon monoxide emitted by outdated or poorly adjusted heating appliances, pollutants likely to contaminate the indoor atmosphere are legion.

Not to mention the airborne bacteria and viruses just waiting to enter our bronchi and lungs. Commercial air purifiers almost all claim almost total elimination of these gases and particles. But do they really keep their promises?

Air purifier:different depollution techniques

All devices claim to offer roughly the same efficiency, but not all work the same way.

The air purifiers by ionization emit ions in the air which agglomerate the fine particles. These then fall to the ground or are collected by the device. They have two advantages:they are quiet and consume little electricity. On the other hand, they can emit ozone, a potentially irritating gas, especially for people with allergies and asthma.
Photocatalytic purifiers are equipped with a catalyst tube coated with titanium dioxide which neutralizes chemical particles, but also bacteria and viruses according to a process developed by researchers at the CNRS in Strasbourg. But their use is not always easy. Some filters must be changed every 15 days and if their instructions for use are not scrupulously followed (poor assembly or poorly arranged filters), they can emit formaldehyde into the air, according to an assessment by the National Agency for health security (ANSES) carried out in 2017.
filtration purifiers seem the most effective and easy to adopt at home. Their principle:a succession of purifying filters. The most sophisticated models that show the best results have a HEPA filter, which captures the finest particles, and an activated carbon filter, which traps gases and volatile organic compounds (VOCs) emitted by combustion tobacco, cleaning products, furniture and building materials. Once treated, the purified air is released into the room.

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Is their performance proven?

Few scientific studies have been done on air purifiers, which cast doubt on the claims of some manufacturers. A test was carried out on various filter models in May 2020 by an independent German laboratory at the request of Stiftung Warentest , the equivalent of the association UFC-Que Choisir across the Rhine.

Verdict:most are pretty good at eradicating airborne pollen. In a room of about 16m2, they eliminate 90% of them. On the other hand, the results on formaldehyde are more disappointing (45% efficiency according to the models tested in Germany). As for cigarette smoke, it all depends on the filter. In new condition, the elimination can reach 90%, but their performance quickly decreases with use. The carbon filter must therefore be renewed regularly so that the device maintains its optimal efficiency.

What about viruses? “We tested the effectiveness of Dyson purifiers from the Pure range (Dyson Pure Hot+Cool™) on the H1N1 flu virus, specifies Michèle Vialette, microbiologist at the Institut Pasteur de Lille. The viruses were nebulized in the air from a closed enclosure, such as those likely to contaminate the respiratory tract. The Dyson Pure HEPA filters have shown a purification efficiency of over 99%". Ideal for reducing your risk of infection during the winter.

But unfortunately no study has yet been conducted with Sars-CoV-2, responsible for Covid-19.