Air Purifiers – Frequently Asked Questions (FAQ’s)

When you’re learning about indoor air pollution, no doubt you’ll have questions. It’ll be the same when researching how air purifiers help clean inside air.

If you buy an air purifier, you’ll want the decision based on the correct information. So you need answers that don’t have any bias.

Below is a list of typical questions we’ve seen. Click to get the answer you need.

What is an air purifier? What does it do?

In simple terms, an air purifier removes pollutants and allergens from the air. In doing so, it produces cleaner and healthier air.

It cleans the air in the room of a building. That room can be in a house or business premises. In fact, any small, medium, or large sized room anywhere. But the room should not be too big. If so, it’ll be beyond the capacity of the largest air purifier available on the market.

In most cases, they are portable. Either small enough for a person to lift with ease. Or with rollers that allow it’s movement from one room to another.

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Why do I need an air purifier?

The US Environmental Protection Agency (USEPA), is often quoted about indoor air quality. The quote is often something like, “the air indoors is somewhere between two and five times more polluted than the air outdoors.”

Another discovery quoted is that “on average a person receives 72 percent of their exposure to chemicals at home”.

I have searched to source these quotes on the USEPA website, without success.

But it makes sense. Most of us do spend a significant proportion of our lives indoors at home or work. And our children are indoors most of their time at school.

Besides, indoor areas these days are built to prevent cold air entering in the winter and hot air in the summer. On the flip side, they’re made to stop heated air escaping in the winter. And stop cold conditioned air escaping in the summer. So it’s a double whammy. What it means is there is no natural ventilation, and the same air keeps recirculating. Recirculation is not so bad if there is no build up of pollutants in that recirculated air.

But if there is build up, breathing or health problems may result. These types of problems could also happen, even if there is some ventilation. Ventilation that draws in pollutants from outside.

Dusting doesn’t help. To a significant part, it sends particles into the air to settle elsewhere. Vacuuming sucks up dust etc. from the floor. But it can’t do anything about the millions of microscopic particles that are floating in the air. These may or may not be pollutants.

In most cases, we’re healthy enough. And if the pollution is insignificant no problems arise.

If pollution is significant, take the following steps first:
* Remove the source of the contamination.
* Reduce the source if total removal is not possible.
* Improve the ventilation.

It’s when the above doesn’t solve the impact of pollution that you may need to use an air purifier.

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How Do Air Purifiers Work?

In basic terms, an air purifier does three things:
* First, it sucks in polluted air.
* Second, it uses one or more ways to remove pollutants from the air it sucked in.
* Third, a fan blows out clean or cleaner air into the room.

An air purifier works best if the door(s) and windows remain shut. The air becomes cleaner after cycling through the air purifier a few times. The number of cycles depends on the capacity of the air purifier.

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How can I tell if I have a problem with the quality of air indoors?

You will be able to tell by the breathing or air related health symptoms you are suffering. These range from sneezing, congestion, itchy eyes, sinus pain, or asthma problems.

There are more accurate ways to tell if you have an indoor air quality problem. You can use a particulate meter. Or one of the latest smart devices that check home pollution on a continuing basis.

Consultation with your medical practitioner is advisable. This way you can confirm the actual cause of your symptoms or if the air quality is at unacceptable levels.

Do this before you consider what action to take and if that should include buying an air purifier.

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What is Indoor Air Pollution?

Indoor air refers to air found in enclosed spaces occupied or used by humans in their daily lives. Here we’re talking about homes, offices, factories, schools, shopping centers, etc.

Indoor air is described as polluted when any harmful contaminants are present.

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What Causes Indoor Air Pollution?

In developing countries, indoor air pollution comes from cooking and heating with open fires. Burning dung, firewood, and coal fill homes with smoke and pollutants. The amount of this type of pollution in the home is estimated to be equal to smoking two packs of cigarettes per day.

The source of indoor pollution in the U.S. is vastly different. Most of us are long past relying on open fires for cooking. Although wood burning fireplaces are still in use. But in some ways, indoor air pollution in the U.S., it is far more insidious.

Tobacco smoke and radon are the two most dangerous indoor air pollutants.

Everyone is well aware of the impact of visible tobacco smoke. And more recently that of secondhand smoke.

But radon is colorless and odorless. It’s a natural occurrence as a radioactive gas when uranium breaks down in rock, soil, and water. The problem is that it seeps up and accumulates in buildings. It is the second-leading cause of lung cancer in the US (after tobacco smoke).

There are two other primary sources of indoor air pollution:

VOC’s. These contain toxic carbon compounds. Compounds released into the air from many things we have in our homes. Like adhesives, household cleaners, paint, perfume, furniture, carpet, paper, aerosol sprays, air fresheners, etc. The list is almost endless. Asbestos also produces toxic VOC’s but don’t expect an air purifier to help here. It is one source of pollution you just have to remove. No question, get rid of it and if you can’t, move to another home.

Living Creatures. Finally, we have living creatures that create indoor air pollution. It’s not just the obvious like cats, dogs, parrots and other household pets. They can be tiny creatures. The ones we cannot see. These include bacteria, mold, dust mites, mildew and many others.

In summary, there are four primary sources of pollution indoors:
* Tobacco smoke.
* Radon.
* Everyday household products and materials.
* Living creatures.

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What are the types of air pollutants in the home?

There are two main types of air pollutants:

Particulate Matter. This kind of matter is physical; it is something the human hand can touch if it is big enough. In the context of pollution, particulate matter is so small we cannot feel it or see it with the naked eye. It can be either in solid or liquid form. And floats in the air.

Gaseous Pollutants. Here we talking about the matter we cannot touch. Like particulate matter it is invisible. It disperses into the outside air if not confined. It loses potency if the dispersion extends over a large enough area.

Of more interest perhaps, is to know the pollutants that fall into each of these two categories.

Particulate Matter includes:
* Tobacco Smoke.
* Animal Dander.
* Pollen.
* Smoke.
* Dust.
* Asbestos fibers.
* Lead

And particles associated with:
* Dust mites.
* Molds.
* Mildew and Fungi.
* Bacteria.
* Viruses.

Gaseous Pollutants include:
* Carbon monoxide.
* Sulfur oxides – particularly sulfur dioxide.
* Nitrogen oxides.
* Ozone.
* Radon.
* Volatile organic compounds (VOC).
* Formaldehyde.

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What Pollutants Do Air Purifiers Remove?

There are many different air purifiers. Their ability to remove indoor air pollutants varies tremendously.

Here we’re talking about the following pollutants:
* Larger particles like dust, hair, animal dander, etc.
* Smaller particles associated with tobacco smoke or smoke in general. And pollen, dust, asbestos fibers, dust mites, molds, mildews, fungi, bacteria, and viruses.
* Odors, chemicals and some but not all gasses, e.g., they don’t remove carbon dioxide.

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What Kinds of Air Cleaning Technologies are Available?

For Particles

When it comes to particles, there are two types of air cleaning technologies in use. Mechanical and electronic.


Cleaning air mechanically involves some form of a barrier. The wall (or filter) can be fibrous or metal with varying sized pores to trap particles.

Metal filters are designed to trap larger particles, in the main. To maintain their efficiency they need cleaning on a regular basis so they don’t clog up.

On the hand, fibrous filters capture smaller particles. The quality of fibrous filters vary. The most efficient are the HEPA filter. These have the added advantage of being free of ozone emission. Some are cleanable and reusable. Others need replacement when they clog up. Maintenance costs may be higher with the latter depending on the quality of your air.


There are three common types of electronic air cleaning technologies used in air purifiers. Ozone generators, Electrostatic precipitators (ESP) and Ionizers.

Both the Air Resources Board (ARB) of the California Environmental Protection Agency (CEPA) and the USEPA have a strong recommendation about Ozone generators. Do not use them in schools, homes or any occupied areas because they produce large amounts of ozone.

ESP’s and Ionizers in general, generate secondary levels of ozone and are safe to use. Just be sure to clean, maintain and operate them according to the manufacturer’s instructions.

For Gasses and Chemicals

Materials used to remove gas and chemical pollution include:

  • Activated charcoal,
  • Impregnated carbon,
  • Advanced military carbon cloth.
  • Aluminum coated with potassium permanganate.

The approach is to draw air through the material. The material either traps or destroys the gaseous contaminants. Overloading is always a possibility. So watch when it’s time to replace.

Other Types of Technologies

The technologies mentioned above are well established.

Other types released more recently, include:
* Photocatalytic oxidation (PCO) for gas impurities.
* Ultraviolet germicidal irradiation (UVGI) for biological contaminants.
* High-temperature heating elements for both gas and biological pollution.
* Electrolyzation of water to destroy organic contaminants.
* The inclusion of “nanofibers” for smaller particles with no increase in airflow resistance.

The jury is still out on these newer technologies.

Note, many air purifiers use a combination of technologies to improve the quality of air.

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What are the different types of filters?

In many ways, the question above provides the answer.

In summary, the different types of filter in common use are:
* Pre-filters – these are metal aimed at capturing large particles.
* HEPA – fibrous filters for smaller particles 0.3 microns and larger.
* HEGA – advanced military carbon cloth for smoke, odors, gasses, smog, and fumes.
* Activated Carbon and Charcoal – for gasses and odors, smoke, chemicals, and fumes.
* Impregnated Carbon – for chemicals like VOC’s

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Why use an air purifier when you can open a window?

An excellent question.

We always talk about going outside “to get some fresh air.” Or leaving the window open to do the same. You’ll get fresh, and by implication, clean and healthy air.

But this depends on where you are.

What if we live in the city or suburbs? Or close to an industrial area? Or there have been wildfires maybe far away?

The air isn’t always fresh and clean.

In these situations, if we open the window, pollutants will come inside. Not just this. These days we have heating units and air conditioners. They need confined spaces to operate with effect. So we don’t want to let in the heat of summer or the cold of winter. Otherwise, they’ll have to work harder and cost extra.

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Portable or In-duct (Central) Air Cleaners: How Do I Choose?

On this site, we only talk about portable in-room air purifiers. We aren’t offering any information about In-duct (Central) Air Cleaners.

What if you want air purification in different rooms (or all rooms)?

We can only suggest buying an air purifier for each room-size area. But when does this become uneconomic? Unfortunately, we can’t help you with this.

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