What is the best air purifier for a large basement?

In this article, we discuss the various types of air purifiers and which amongst them is the best when it comes to maintaining the optimal indoor air quality in a large basement.

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 odours present in the air.

Why should we care about the air quality in a basement?

The average American spends 93% of their life indoors. 87% of their life is inside buildings, then another 6% of their life is in automobiles. 

Over the last several years, a significant amount of scientific reports provide evidence of air pollution inside buildings and homes, referred to as indoor air pollution (IAP), which is more serious than outdoor air pollution, even in industrialised cities and metropolitan areas.

Thus, a person has a higher health risk from indoor air pollution than from outdoor air pollution. 

Furthermore, people who spend relatively more time indoors are much more susceptible to the effects of IAP. 

“Sick building syndrome” is a term used for situations where building occupants exhibit acute health issues that appear to be linked to time spent within the building, but no specific illness or cause can be identified. 

The common pollutants linked with this are carbon monoxide, nitrogen dioxide, suspended particulate matter (PM10 and PM2.5), radon, and formaldehyde. 

Basement areas are defined as enclosures placed directly under the building. These rooms are usually built below ground level, so they are prone to leakage problems, and usually lack adequate ventilation and heat. 

These factors play a major role in increasing the relative humidity of the room, which favours the growth of mold and mildews. 

The air quality in these rooms is primarily affected by factors such as (i) various items stored such as unused furniture, solvents and chemicals used for cleaning or hobby purposes, paints, and gasoline products (ii) moisture content, (iii) presence of mold and mildew, (iv) presence of furnace or boilers; and (v) dust and dander. 

Furthermore, these rooms usually have very limited air exchange, which causes a build-up of PM within these rooms. 

Certain products such as furniture release emissions more or less continuously, while other sources (e.g.: smoking, air fresheners) release emissions intermittently. 

Thus, it is important to ensure the air quality of the basement is well-maintained. To determine the best practical approach for improving air quality, it is crucial to identify the major contributors to IAP in the basement. 

A way to judge whether the basement has IAP is by identifying potential sources of pollution. 

For example, the characteristic “basement smell” is caused due to putrefaction processes that occur in high humidity conditions, and with the participation of microorganisms. 

Such conditions indicate poor ventilation and high relative humidity, which is characterised by the presence of moulds on walls and articles such as clothes, shoes, etc., and the spores arising from this become a biological air pollutant. 

Sometimes, symptoms that are related to IAP (eg.: irritation of the eyes, nose and throat, headaches, fatigue, etc.), indicate the presence of dust, solvents, and other PM. 

Do air purifiers help?

Based on research and countless testimonials from multiple users, yes, air purifiers are helpful. Air purifiers are devices that, as the name suggests, purify the indoor 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 carbon filter, and so on, which are mainly designed for widening the range 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.

Conclusion – Which air purifier is the best for a basement?

Based upon what we’ve seen so far, 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.

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.


Can we keep an air purifier on at all times?

Yes, you should keep your air purifier on at all times. This is because the pollution is more or less continuous in nature, meaning that as long as a source is present, so is air pollution, including dust.

If you turn off your air purifier, the dust particles start aggregating in the indoor air once again, which would eventually affect the health of the occupants adversely.

Furthermore, air purifiers do not consume a lot of electricity for operation, therefore making it feasible to be kept on at all times.

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.


Leave a Comment