Are there any safe air purifiers?

In this article, we discuss which air purifiers are safe for using indoors and do not have any particular side effects on the health of the indoor occupants.

Are there any safe air purifiers?

Yes, most of the commercially available air purifiers are considerably safe for use. However, air purifiers that use HEPA and activated carbon filters are the safest option with respect to the other types of air purifiers available in the market.

What is an air purifier and why do we need it?

Air purifiers are devices which, as the name suggests, clean the ambient air. There are mainly two types of air purifiers, namely:

  • High efficiency particulate air (HEPA) filters
  • Air ionisers

These air purifiers can have additional components, such as a UV light chamber, activated charcoal filter, and so on, which are mainly designed for widening the spectrum of the device’s efficacy against various pollutants.

Many people wonder whether an air purifier is the right investment. However, in the current scenario, where air pollution is prevalent and worsening with each passing day, especially in urban areas, air purifiers are very vital.

Air pollution is the presence of undesired substances in the form of solids, liquids, or gases, which are suspended in the ambient air, and can adversely affect human health.

These pollutants can be especially harmful if present in the indoor environment. The average human being spends more than 90% of their total lives in an indoor environment, with more than 80% of it inside a building.

Indoor air, just like outdoor air, is susceptible to pollution. Indoor air can get polluted when pollution from outdoors infiltrates through openings such as doors, windows, cracks, seeps, etc.

Indoor air can also get polluted from indoor sources, which can arise from things such as furniture, household items, solvents and dyes, spores from mold and mildew, combustion of fuels and firewood, and hobbies/activities such as smoking, etc.

The pollutants generated from these sources have been shown to adversely affect human health, and continuous exposure to elevated concentrations can cause many serious issues, such as cancers, respiratory and cardiovascular disorders, and even death.

This is where air purifiers come in. They help to get rid of the pollutants in the indoor air, thereby keeping it clean and fit to breathe.

Various types of air purifiers

There are mainly 3 various types of air purifiers that are commercially available in the market. These are:

  • HEPA filters
  • Air ionisers
  • Activated carbon filters

We shall discuss these in more detail.

HEPA filters

These air purifiers are also known as passive air purifiers. They simply pull in air from the indoor air, pass it through the filter, and release the purified air back in the enclosure.


The HEPA filters are very popular nowadays, as they have an efficiency greater than 99% against particles that are equal to or greater than 0.3 microns in diameter.

These air purifiers also help to get rid of odor-bearing substances such as smoke particles, dust, volatile organic compounds (VOCs), and so on.

Side effects

In the current scenario, the covid pandemic has been a prevalent issue. Studies have shown how the virus can spread indoors from infected articles to healthy people. Hence, prevention is necessary.

Furthermore, HEPA filter air purifiers fail to catch virus particles, since the typical size of a virus is less than the effective range for the air purifier’s functioning.

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. This provides the optimal dark and humid condition within the filter itself that promotes the growth of mold and bacteria.

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.

Air ionisers

Air ionisers are also known as active air purifiers. They release negatively charged ions into the ambient air. These negatively charged ions attract pollutants that have a positive charge and combine with them.

Once they are combined, the pollutant particle becomes too heavy to stay suspended in the ambient air. Therefore, they get deposited on surfaces.


Studies have shown that air ionisers are effective in getting rid of allergens, which include pollen, spores from mold, animal dander, dust, and so on.

Air ionisers interact with odor causing molecules as well. The ions interact and bind to the bonding sites of the odor causing pollutants.

This, in turn, renders the pollutants ineffective, due to which the odor cannot be picked up by the nose. Therefore, air ionising necklaces are useful especially when one is passing through polluted areas such as open dumps or sewages, traffic, and so on.

Side effects

Conventional air purifiers are known for their high efficiency rate of removing pollutants from the ambient air. However, the same cannot be said for ioniser air purifiers.

Ioniser air purifiers work by generating ions at the rate of thousands per minute. They do so by using a mechanism called corona charging, in which oxygen molecules can also get broken down, which in turn react with each other to form ozone.

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.

Activated carbon filters

Activated carbon filters are thin membrane like filters which help to get rid of gaseous pollutants as well as other undesirable gaseous species.


Activated carbon filters are the best when it comes to getting rid of odors, irrespective of its nature and constituents. They are usually included as an additional component in air purifiers with HEPA filters.

The activated carbon filter absorbs the odor and gaseous pollutants present in the indoor air, when it is made to pass through the filter.

Not only does it help to get rid of odors from various sources, it also helps to get rid of dangerous gaseous pollutants such as radon and carbon monoxide, both of which can be lethal when one is subjected to elevated concentrations of these.

Side effects

Activated carbon filters are very thin and flimsy. This can cause
Them to be easily damaged. Therefore, such filters cannot be used as a stand alone filter.

Furthermore, these filters are very sensitive to particle loading, and tend to get overloaded quite easily with respect to the HEPA filters.

Which one is the safest?

One should refrain from investing in an ioniser air purifier. Even though it has some advantages, the side effects outweigh those, particularly the generation of ozone alone.

In some places, such as California in the United States, air purifiers that produce ozone are outright banned for manufacture and sale in the entire state. 

Therefore, for people living in these areas or visiting these areas, it would be useless to use or buy an ioniser air purifier.

Therefore, your best bet would be using an air purifier which uses both, a HEPA as well as an activated carbon filter. This helps to get rid of particulate matter as well as odors present in the air.

Ways to prevent and minimise the side effects

HEPA filter air purifiers are meant to make life easy and the air clean for the user. However, we have seen that in some cases, it can have the opposite of the desired result.

However, these issues have solutions which help to minimise or prevent them from happening in the first place. These methods include:

  • Regular maintenance and replacement of HEPA filters.
  • Pairing it with other devices under certain conditions.

We shall discuss the importance of these methods.

Regular maintenance and replacement of HEPA filters

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.

HEPA filters have a fixed life span till which they can work against pollutants efficiently. However, with time, this efficiency starts to decline, since more and more particles are stuck in the filter media.

Therefore, it is ideal to replace your HEPA filters. Usually, the manufacturing company themself provide the time span in which the HEPA filter should be replaced.

Pairing it with other devices under certain conditions

When using an air purifier in unfavourable conditions, it would be ideal to first use appliances that help to alleviate those conditions in order for the air purifier to perform efficiently.

For example, if the indoor humidity levels are too high, one should first use an air dehumidifier in order to bring down the humidity conditions to an ideal range, after which the air purifier should be used.


In this article, we have seen that air purifiers that use HEPA and activated carbon filters are the safest option with respect to the other types of air purifiers available in the market.

Although there are certain side effects associated with these filters, those factors can be prevented by making changes externally, therefore allowing the air purifying device to perform efficiently.


How to tell if my air purifier is producing ozone?

Although manufacturers usually mention it along with the product, sometimes, due to technical issues, your air purifier might start generating ozone. 

You can tell whether there is ozone by looking out for some of the  most common symptoms such as a feeling of irritation in the eyes, nose and throat. 

Some people may also experience respiratory or heart symptoms such as shortness of breath, chest pain, and wheezing.

Where should I place my air purifier?

Ideally, you should place your air purifier in a location where the highest rate of air exchange takes place. Air exchange refers to mixing of two different types of air, which in this case refers to indoor air and outdoor air, and from one room to another.

This is because most of the pollution inside the house comes from outdoor sources. This in turn could spread to other rooms of the house. Hence, by placing an air purifier here, spread of pollutants within the house gets hampered.

Furthermore, the ideal place to keep an air purifier is to mount it on a wall, ideally 3-5 feet above the ground. This is because air moves horizontally as well as vertically, and this placement would ensure that the particles present in either air motion get successfully trapped by the air purifier.

How often should I replace my air filters?

The frequency of replacing your air filters depends upon the indoor air quality of your house. If you live with a small number of people, have pets, and are near a polluted area, you might need to replace your filters as early as 1-2 months.

However, if you live alone with no pets or other animals, you can replace your filter once every 6-12 months.