How air purifiers work at home

In this article, we discuss the working of an air purifier for indoor settings, more specifically, at home. We elaborate on its efficacy, what range of pollutants can it deal with, and finally the advantages and disadvantages of an air purifier.

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.

How air purifiers work at home

As discussed before, there are two types of air purifiers, namely:

  • Air purifiers with HEPA filters
  • Air ionisers

We shall discuss these in more detail.

Air purifiers with 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.

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.

Which one is better?

While both are good in their own ways, air purifiers with HEPA filters are by far a better option than air ionisers.

The main reason for this is that ionisers simply remove particles from the air, which get deposited on floors, surface of items, and ceilings.

These particles can cause allergies, and need to be cleaned and removed manually. Furthermore, ionisers produce a considerable amount of ozone in their working, when compared to HEPA air purifiers.

Ozone is a highly reactive gaseous molecule which is naturally present in the upper layers of the atmosphere, where it absorbs the sun’s damaging ultraviolet radiation.

When present in the lower levels of the atmosphere, however, it acts as a pollutant, and can have serious adverse effects on human health, which also includes afflictions related to the cardiovascular and respiratory systems.

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.

What are air purifiers efficient against?

Air purifiers are mainly designed to remove particulate matter, or simply 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.

They can also act as adsorbents, allowing various elements to be stuck to their surface, which in turn can prove more harmful when inhaled.

Various sources of PM in a house

In a household, PM can arise from many sources. Some of these sources include:

  • Spores from mold
  • Asbestos
  • Allergens, such as animal dander, pollens
  • Smoke

Let us discuss these in more detail.

Spores from mold

Mold refers to the growth of fungal material on items such as walls, clothes, etc., in places where temperature is low and the relative humidity is high.

These are commonly seen in areas of the house where seepage occurs, or rooms such as the kitchen, bathroom, or the basement, where the ideal conditions exist.

The spores generated from mold have adverse effects on human health, and certain mold species can even prove to be fatal.

Air purifiers help to remove the spores from the ambient air. Although care should be taken as to not run the device in high humidity levels, as its efficacy gets reduced considerably.

Therefore, it is ideal to pair your air purifier with an air dehumidifier, which first brings down the humidity levels of the room, thereby allowing the air purifier to work efficiently.


Asbestos is a mineral fiber that was used earlier in a variety of construction materials since it acts as an insulator and a flame retardant. 

Although it is now banned in 55 countries, it is still used in major countries such as China, India, Russia, Canada, and the United States, although the EPA and CPSC have banned several asbestos products. 

Asbestos is purely an indoor air pollutant, as it concentrates in the indoor air due to activities such as remodelling, cutting, and sanding of asbestos-bearing products.

Elevated concentrations of respirable asbestos particles can cause lung cancer, mesothelioma (a cancer of abdominal and respiratory linings), and asbestosis (irreversible scarring of lung tissues).

Air purifiers can pick up asbestos particles from the indoor air, although it would be better to eliminate asbestos particles by repairing old asbestos-bearing materials by sealing or by covering them.


Allergens include substances such as dander from animals, pollen, and dust mites, which cause irritation to the respiratory system, with symptoms such as running nose, irritation in throat and nose, watery eyes, and so on.

These particles are comparatively larger than other types of PM pollutants present in the air, hence get easily entrapped by an air purifier.


Smoke is one of the worst pollutants, in both outdoor air as well as indoor air. It is generated by combustion of fuels such as gasoline, firewood, coal, dried dung, and from other sources such as cigarettes.

Various studies have shown how exposure to smoke can adversely affect human health, and can even cause illnesses related to the cardiovascular and respiratory system.

Cigarette smoke is the most toxic pollutant. Studies have shown that active smokers, as well as people that are subjected to secondhand smoke, are at a much higher risk of developing cancer of the mouth, throat, or lungs.

Smoke particularly affects certain groups of individuals, such as children and older people, people that use solid fuels for their energy needs, and so on. In children, there are higher reported cases of hospitalisation due to illnesses caused from exposure to smoke. 

Furthermore, it was also shown that respiratory illnesses such as asthma, emphysema, COPD, etc., were reported in much higher numbers for smokers, secondhand smokers, and people subjected to combustion-based pollution.

Air purifiers serve an important purpose of getting rid of the smoke particles present in the indoor air, and along with it, get rid of the odor associated with smoke.


Air purifiers work in two different methods – by either passing polluted air through a filter, or by releasing negatively charged ions in the ambient air.

In a typical home setting, air purifier work best against particulate matter (PM), which mainly arise from various sources, such as mold, allergens such as pollen, animal dander, dust mites, etc., asbestos, and particles in smoke.

Amongst the two types of air purifiers, the HEPA air purifiers are the better choice, due to their high efficiency and wide range of applicability.


Can air purifiers get rid of odors?

Yes, air purifiers can get rid of odors. Most of the air purifiers, such as the one by Hathaspace, come with an activated carbon filter, which gets rid of unpleasant odors present in the air.

Can air purifiers work against coronavirus?

There have not been a significant amount of studies which prove or disprove the effects of air purifiers on the novel coronavirus. However, the existing research has not found any significant link between the use of air purifiers and the spread of covid in an indoor environment. Therefore, it is safe to assume that air purifiers do not work against coronavirus.

Where is the best place to keep an 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.

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