Are air filters worth it?

In this article, we discuss whether air filters are a worthy investment for keeping the indoor air clean and safe for breathing. We also discuss their types, their working mechanism, and which one is the best amongst them.

Are air filters worth it?

Yes, air filters are a worthy investment to make. Air filters, as the name suggests, clean the air, thereby removing toxins and other harmful substances from the indoor air.

They help to reduce the risk of illness due to poor air quality, therefore proving beneficial. However, there are certain scenarios when air filters might be doing more harm than good.

What are air filters?

Air filters refer to the equipment that are responsible for keeping dust and other undesirable substances that can be present in the indoor ambient air.

Air filters are the structural and the functional unit of an air purifying device. They come in many forms, as different filters cater for different types of pollutants.

The air purifiers that people use in homes and offices, as well as the air scrubbers, come with a HEPA (High Efficiency Particulate Air) filter. 

There are also other types of air filters, such as the activated carbon filter, which helps to capture gaseous pollutants as well as odors from the indoor air.

Why do we need an air purifier?

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.

What are air filters efficient against?

Air filters, especially the HEPA filters, 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 filters 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.

How often should I replace the air filters in my appliances?

Usually, manufacturers provide a time period till which the air filters will work efficiently. However, if you do not know what is the said period, you can make a fair estimate on your own.

First, consider the amount of time the appliance runs. For appliances that run for a longer period, say air purifiers and HVACs, you would need to replace their filters earlier with respect to the other appliances.

Furthermore, if your appliance shows various signs such as bad smell, overheating in a comparatively shorter amount of time, or if you detect bad odors or face allergy-like symptoms when these devices are running, it is a sign that you should replace your filters as soon as possible.


Air filters are responsible for getting rid of particulate matter from the ambient indoor air, thereby reducing the chances of illnesses related to exposure to polluted air.

These PM pollutants can arise from various sources, which include spores and pollen, asbestos, smoke, and other forms of allergens.


Can air filters also cause harm?

There are certain conditions when air filters can cause harm to your health. These scenarios include:

  • When using old and ill-maintained filters.
  • Running air purifiers in high humidity settings
  • When the device produces ozone

Let us discuss these in more detail.

When using old and ill-maintained filters

Old and ill-maintained filters are loaded with dust and other particles which affect the optimal functioning of the air filter. They do not filter out any particles from the indoor air.

This in turn can cause the pollutants to persist in the indoor environment, which in turn can adversely affect the health of the occupants. Therefore, it is vital to replace air filters on a regular basis in order to avoid this.

Running air purifiers in a high humidity settings

When an air filter is used in a high humidity setting, its efficiency decreases significantly. This is because humid air is more heavy than normal air.

Furthermore, humid air can also trigger the growth of mold and mildew in the filters itself, which in turn can further aggravate the indoor air quality when the air purifier is being used.

When the device produces ozone

Certain air purifiers use ionisers, which produce ions in order to capture dust particles causing them to settle, as well as prevent them from resuspending in the air.

However, ionisers also produce ozone, a highly reactive gas with a pungent smell, which can cause bronchitis and can trigger asthma attacks in people susceptible to it.

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, the 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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