Home air purifiers: are they really useful in the fight against pollution and allergens?

Those most sensitive to air pollution and allergens, and in general all those who wish to breathe cleaner air, may consider purchasing a home air purifier.

What are air purifiers used for?

Air pollution is a problem in many cities around the world, but in summer and in dry climates, the lack of precipitation can make it worse. Add to this the flowering season for pollen-allergenic plants, and many people can find it difficult to breathe properly.

Olfactory pollution: when you can't see or hear toxic substances, but you can smell them.

As well as causing allergies, pollution has serious health consequences for everyone exposed to it. The air pollutants that most affect health are :

Particulate matter (PM2.5 and PM10): these are tiny particles that can be inhaled into the lungs and cause respiratory problems. PM2.5 particles have a diameter of less than 2.5 microns (thousandths of a millimeter), while PM10 particles have a diameter of less than 10 microns. They can come from a variety of sources, such as vehicle exhaust, industrial emissions and dust from construction sites and roads.

Nitrogen oxides (NOx) are gases that can cause respiratory problems and contribute to the formation of smog (a combination of smog and pollution). They are produced by vehicle exhaust and industrial emissions.

Sulfur dioxide (SO2): is a gas that can cause respiratory problems and contribute to the formation of acid rain. It is produced by the combustion of fossil fuels such as coal and oil.

Carbon monoxide (CO): a potentially lethal gas in high concentrations. It is produced by vehicle exhaust and other combustion processes.

Ozone (O3): the same gas that protects us from ultraviolet rays in the upper atmosphere can cause health problems if inhaled, such as irritation of the respiratory tract and aggravation of asthma. It is formed when nitrogen oxides and volatile organic compounds (VOCs) react in the presence of sunlight.

Volatile organic compounds (VOCs): these are chemical substances that affect the immune system and are sometimes carcinogenic. They are emitted by a variety of sources, including vehicle exhausts, industrial chimneys and certain consumer products such as paints and solvents.

In addition, other elements floating in the air in the home can cause nuisance:

Dead skin cells from humans and pets, which accumulate as dust and serve as food for dust mites.

MitesThese microscopic arachnids feed on dead skin cells and can be a major source of allergens.

Pollen Pollen from trees, grasses and other plants can enter indoor environments and contribute to allergies.

Pet hair Pet dander: pets shed dander and hair, which settles as dust.

Mould spores Moulds can grow in damp indoor environments and release spores into the air, which can cause respiratory problems.

Bacteria and viruses: some of these micro-organisms can survive in dust and cause respiratory and other health problems.

Chemicals: chemicals from cleaning products, personal hygiene products and other sources can contribute to indoor air pollution.

With all these potentially toxic pollutants in the air around the home, it's only natural that sensitive people suffering from asthma, allergies or other respiratory ailments should look for ways to breathe cleaner air in their homes. That's where air purifiers come in.

How do air purifiers work?

Most air purifiers have a similar basic mechanism: a fan draws air into the room and passes it through filters, allowing the air to emerge cleaner. There are several types of air purifier on the market, depending on the type of technology they use to remove pollutants. It's worth noting that some of them combine several technologies. Here are some of the most common types:

High-efficiency particulate air (HEPA) filters High Efficiency Particulate Air (HEPA) filters: these are the most common purifiers, and are certified for their efficiency. HEPA filters are guaranteed to trap 99.97% of airborne particles larger than 0.3 microns, including smaller allergens such as pollen, dust mites and pet dander. HEPA filters also effectively remove dust, smoke, chemicals and asbestos.

Activated carbon filters: these filters effectively remove odors and volatile organic compounds (VOCs) from the air. They work by absorbing contaminants from the filter surface, and are often combined with HEPA filters.

Ultraviolet (UV) light: UV-C light is used to eliminate bacteria and viruses that may be present in the air. UV air purifiers are often used in hospitals and other healthcare facilities to prevent the spread of airborne diseases.
Ozone generators: Although it may seem contradictory, these air purifiers work by producing ozone, which reacts with air pollutants and breaks them down into harmless substances. However, ozone generators can also produce harmful by-products and are not recommended for domestic use.

Electrostatic precipitators: these air purifiers use an electrostatic charge to attract and trap air pollutants. They are effective at removing large particles, such as dust and pet hair, but less effective at removing small particles, such as allergens and bacteria.

Ionizers: these air purifiers release negatively charged ions into the air, which attach themselves to positively charged pollutants and cause them to fall to the ground. However, ionizers can also produce ozone and are not recommended for domestic use.

How to choose the right air purifier?

The most important thing is that it should be equipped with HEPA filters, which may or may not be combined with other technologies mentioned above. But it also needs to be sufficiently powerful.

When buying an air purifier, we often measure the CADR (Clean Air Delivery Rate), which determines the flow of clean air measured in cubic meters of clean air per hour.

To calculate the cubic meters of a room, multiply the surface area by the ceiling height, which is generally two and a half meters. Thus, a 12-square-meter room will have 30 cubic meters. If the purifier has a CADR of 60 m3/h, it will be able to completely purify the air in the room in half an hour.

Are air purifiers effective?

Air purifiers come in a wide variety of sizes and styles, from small portable units to larger models that can purify the air in an entire building, with prices ranging from under $100 to over $500. Some air purifiers are designed for specific purposes, such as eliminating cigarette smoke. If you're concerned about your health and pollution levels, are home air purifiers worth it?

A study conducted in three European cities showed that home air purifiers reduced PM2.5 concentrations in bedrooms by 45% to 69%. Another study examined the effectiveness of particulate air purifiers in improving indoor air quality in the classrooms of three public schools in the northeastern USA. The study showed that the purifiers were effective in removing PM2.5 particles and other elements from classroom air.

On the other hand, a study of eight residential homes in the USA found that air purifiers reduced PM2.5 concentrations by 96% in the short term (5 minutes) and long term (2-5 days), by 29-37% for particulates and bacterial endotoxins, and by 26% for lead.

During desert dust storms, air purifiers were used in the homes and classrooms of asthmatic schoolchildren and adults with atrial fibrillation in Cyprus and Crete, while reducing ventilation. The results showed that this was an effective protective measure that significantly reduced exposure in high-risk population groups.

Overall, home air purifiers can be effective in improving air quality in the home, notably by reducing the concentration of particles, pollen and dust. Bear in mind, however, that their effectiveness can be affected if the size of the room is not properly calculated. It's important that the air purifier you choose has plenty of margin to allow for air purification in exceptional situations, such as cooking smoke or a garbage can fire.

How do I maintain an air purifier?

Like all household appliances, air purifiers require maintenance, particularly of the filters, to maintain their efficiency and extend their service life. Here are some general tips:

Replace filters regularly according to the manufacturer's instructions. Filter life depends on the level of contamination.

Clean the pre-filter: most purifiers are equipped with a pre-filter before the HEPA filter, which traps larger particles such as dust and pet hair. It should be cleaned regularly to prevent clogging.

Clean the outside: the outside of air purifiers can accumulate dust and other contaminants over time.

Check the fan: air purifiers' fans can become clogged with dust and other contaminants, and should be checked regularly.

We hope you've learned more about air purifiers.