How air purifiers can be harmful

This article discusses the potential adverse effects of air purifying devices on human health. Additionally, we discuss alternatives and methods which help to minimise stop the side effects of air purifiers.

Can air purifiers be harmful for health

Air purifiers are supposed to help alleviate human health. However, under certain circumstances, they can do more harm than good.

Why should you get an air purifier?

Air purifiers are devices which, as the name suggests, clean the indoor air. Air pollution is a prevalent problem, not just outdoors, but indoors as well.

Indoor air pollution is a serious issue, as the average human being spends more than 90% of their total time within an enclosure, with more than 80% of it being inside a building.

Over the previous years, air pollution has been on the rise, mainly due to human activities, especially in urban areas. The processes that contribute the most towards the exacerbation of air quality include:

  • Traffic related air pollution (TRAP)
  • Industrial emissions
  • Combustion of fossil fuels and firewood

Apart from these, in a typical indoor environment, air gets polluted from infiltration of outdoor pollution from openings such as doors, windows, cracks, seeps, etc.

In an indoor setting, there are various sources of indoor air pollution which include furniture, household items such as solvents, paints, dyes, etc., asbestos, and so on.

Amongst these, the worst pollutant is particulate matter, or simply PM. Air purifiers are mainly designed to remove PM from the indoor air. 

PM refers to particles, either solid or liquid, that are mixed and suspended in the air. They are a major part of air pollutants, and have a variety of natural and anthropogenic sources. They usually range between 2.5 to 10 microns (PM10 and PM2.5).

Particulate matter is a major contributor to both long term and short term illnesses. There are many well-documented studies that have shown progression of illnesses with an increase in the concentration of PM. 

PM2.5 is of a major concern, as it can easily enter the lower respiratory tract, therefore causing more serious cardiac and respiratory issues.

Moreover, PM is also linked to premature deaths of people who had pre-existing health issues such as people with cardiac or respiratory issues, obesity, asthma, and so on.

Apart from this, air purifiers can also get rid of allergens such as animal dander and pollen, odors, and airborne vectors of diseases.

When does an air purifier become harmful for health?

Given the benefits offered by air purifiers, it is hard to believe that air purifiers can sometimes be harmful for health as well. The scenarios in which air purifiers can be harmful include:

  • Generation of ozone (O3)
  • Breeding ground for mold and bacteria
  • UV rays

Let us discuss more about these in detail

Generation of ozone (O3)

Certain air purifiers, particularly the air ioniser purifiers, produce ozone gas as a byproduct of the reaction to generate charged ions.

Ozone is a gas that is naturally formed by interaction of light with oxygen molecules. It is a vital gas in the upper atmosphere, where it blocks the harmful UV rays from entering the atmosphere.

However, when present at the ground level, it has negative implications on human health. It is one of the major pollutants in photochemical smog, which is formed when different species released from vehicular emissions react with each other.

Ozone acts as an irritant, due to its pungent odor. It can cause wheezing, irritation in the nose and throat, runny nose, watery eyes, difficulty in breathing, and so on.

Additionally, ozone can also worsen the condition of people who are suffering from diseases such as asthma, emphysema, and bronchitis. 

Breeding ground for mold and bacteria

For cases where the air purifier is installed in rooms with high relative humidity, one of the common substances to get trapped in the air filter would be mold and bacteria.

If the filter is left on at all times, the amount of water vapour that gets entrapped in the filter will also increase.

Not only will this reduce the efficiency of the filter, it will also serve as a breeding ground for mold and bacteria, which in turn would be propagated through the air purifier.

UV Rays

UV rays in a filter kill all the particulate matter that passes through it. UV technology is commonly combined with air filters to attain efficiency and maximum air quality.

Facts are also astonishing for humans as the filter fixed with UV technology also tends to break the oxygen and water molecules into ozone and hydroxyl. The broken down elements will then react with other pollutants and turn even more harmful.

UV air purifiers, thus, may not be an effective solution for particulate matter. Many UV air purifiers miss out on trapping microorganisms because of shielding provided by the particles.

How to prevent harmful effects of air purifiers

As we’ve seen, it is vital to keep the negative effects caused by air purifiers in check, so that it can deliver the way it was meant to be.

Therefore, we should take certain steps in order to ensure that the air purifiers are performing adequately. This can be done in the following manner:

  • Opt for air purifiers that have minimal ozone production
  • Avoid running air purifiers in high humidity settings
  • Clean the air purifying filters regularly
  • Get the device serviced on a regular basis

Let us discuss these in more detail below.

Opt for air purifiers that have minimal ozone production

There are many commercially available air purifiers which have none to very minimal ozone production. Usually, buying an air purifier with a True HEPA filter would be your safest option.

Similarly, one should refrain from investing in an air ioniser purifier, since they generate a lot of ozone in their working. Furthermore, these purifiers aren’t as efficient as the HEPA filter air purifiers.

Avoid running air purifiers in high humidity settings

As discussed above, running an air purifier in high humidity settings would reduce the efficiency of air purifiers, as well as create conditions which make the growth of mold, bacteria, and spores favourable, within the air purifier unit itself.

Therefore, one should avoid running an air purifier in high humidity settings. However, it is vital to install a dehumidifier along with the air purifier.

This would help to reduce the humidity levels in the room/house, which in turn would make it easier for the air purifier to run optimally.

Furthermore, low humidity levels created by the dehumidifier would also help to hamper the growth of bacteria and mold within the rooms itself, thereby making the indoor air cleaner.

Clean the air purifier filters regularly

Certain air purifying devices have filters and other accessories which enables the user to clean out the HEPA filters themselves. 

This is beneficial because it helps to reduce the particulate load present on the air purifier filters, and can also help identify whether there is any growth of mold and bacteria.

For older filters, it would be ideal to replace the filters altogether, as the efficiency of filtration falls steadily with time.

Get the device serviced on a regular basis

It is ideal to get your air purifier serviced on a regular basis by the technicians, as it is beneficial for the long run. This is also very helpful since any latent issues could also be identified and dealt with before it becomes a menace.

Other FAQs about Air Purifiers and Filters that you may be interested in.

How air purifiers help

How air purifiers work at home

Side effects of Air Purifiers


Air purifiers are devices designed to keep the indoor air clean. However, there are certain circumstances in which they do more harm to the indoor air quality than good, which in turn could adversely affect the health of the occupants.

This can happen due to generation of ozone, running in humid conditions, or in the case of air purifiers with a UV chamber, formation of undesirable pollutants.

Some air purifiers to consider


Can keeping the air purifier on all the time be harmful for me?

If you are using an air purifier which uses a HEPA filter to clean the air, then no, keeping the device on at all times is safe for you. It is advantageous to keep your air purifier on at all times, since air pollution is more or less continuous in nature. 

However, for certain types of air purifiers, like the air ionisers, because of the production of ozone and the typically low efficiencies, cannot be left on at all times, as they can further exacerbate the air pollution indoors.

Can the UV Rays generated by the air purifier cause cancer?

No, the UV rays generated by the air purifier does not cause cancer. However, the rays can give rise to Volatile Organic Compounds, or simply VOCs.

Exposure to VOCs can cause short term health effects such as irritation of the eyes, nose and throat, headaches, and nausea. Long term exposures can adversely affect the liver, kidneys, and the central nervous system. 

Therefore, if you experience any of the above mentioned symptoms while your air purifying device is operating, it would be ideal to get it checked.

Do air ionisers generate more dust?

Air ionisers do generate more dust, which further exacerbates the air quality of the indoor environment. Air ionisers interact with the charged pollutant particles by sticking to them, causing them to become too heavy to stay suspended in the ambient air.

This would in turn cause deposition of dust on surfaces such as carpets, tables, etc., which in turn would exacerbate the effect of dust already present indoors.

However, it would be ideal to pair it with an air purifier containing a HEPA filter, as it would increase the efficiency with which the indoor air gets cleaned.

Is it bad to sleep next to an air purifier?

No, it is good to sleep  next to an air purifier. This is because the air purifier keeps the air clean in the room where you are sleeping, which improves the quality of sleep.

Furthermore, air purifiers do not make much noise when they are operating, so they would not disturb your sleep. Therefore, it would be ideal to place the air purifier in your bedroom, at a distance of about 5-6 feet from your head.


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