What Is An Air Purifier?

According to Pure Earth, the air all over the world is getting more and more airborne contaminants. And this is why inventors created home air purifiers.

You may have a plain concept, but can you answer “What is an air purifier” in the most comprehensive way? We can.

And in this article, apart from giving you the detailed definition of an air purifier, we also explain about types of air purifiers, what to look for in an air purifier, and what differs an air purifier from an air cleaner.

What is An Air Purifier?

An air purifier is an electronic device dedicated to removing air pollutants such as dust mites, mold spores, mildew, dust pollen, bad odors, bacteria and viruses that can result in respiratory problems like allergies or asthma from the air.

The majority of air purifiers mainly capture these airborne particles in their filtration system rather than destroy them.

Types of Air Purifiers

1. HEPA air purifiers

A HEPA air purifier model

HEPA air purifiers can be divided into two categories. But regardless of types, it is the filtration system that purifies the air.

The inferior HEPA-type filter can remove 99 percent of airborne particles at 2-micron size from your home air. Meanwhile, a True HEPA filter or HEPA filters remove 99.97% ultrafine particles at 0.3 microns (e.g., Rabbit Air air purifiers).

The internal fans of these portable air purifiers pull particulate air into filters then filters remove pollutants from the air circulating by trapping them. There might be a range of filter types from a pre-filter, a carbon filter, a HEPA (high efficiency particulate air) filter to furnace filters.

The initial pre-filter captures bigger particles like hair or dust. The carbon filter is for removing gaseous pollutants, and the HEPA filter will trap tiny microbes.

After going through that series of filters, clean air will come out from the vent of the indoor air purifier.


  • Widely available
  • Great for trapping dust mites, mildew, pollen, pet dander, mold, virus, and bacteria


  • Cannot tackle odor and smoke without a carbon filter
  • Require replacement filters annually

2. Odor eliminator

An odor eliminator

Odor eliminators are also portable air purifiers and work much like HEPA air purifiers.

This air purification method typically uses baking soda filters, carbon sheets, Granular Carbon filters or Activated Carbon filters to fight against bad odors.

Activated carbon will absorb pass-by pollutants and chemical fumes such as radon, CO, ammonia, sediment, chlorine, and VOC (Volatile Organic Compound).


  • Excellent for odor and smoke removal
  • Budget-friendly


  • Ineffective against non-smoke particles
  • Require replacing filters every few months

3. UV Air Purifier

UV Air Purifier

A UV air purifier typically works based on advanced ultraviolet germicidal technology. The machine consists of a bottle sterilizer, water purifier, and UV lights.

UV air purifiers are good at tackling many types of fine particles, including gaseous pollutants. Furthermore, UV-C radiation will spread through your house air without emitting great amounts of ozone, so it is very safe.

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Ultraviolet light is also scientifically proven to kill germicides and bacteria very well.


  • Most useful for eliminating bacteria and viruses
  • Destroy pollutants rather than capturing them


  • Effectiveness decreases over-time.
  • It takes longer to eradicate airborne irritants
  • Not long-lasting

4. Photocatalytic Air Purifier

Photocatalytic Air Purifier

A Photocatalytic Air Purifier utilizes PCO (Photocatalytic Oxidation) filtration that can remove contaminants at the size of 0.001 microns. Therefore, it is even more effective than a HEPA filter and can eradicate even the smallest viruses.

This type of device creates a photocatalysis process to boost the natural disintegration of organic substances. In detail, the broad-spectrum UV light will react with a thin titanium dioxide film to promote the oxidization of microorganisms, which makes them absorbed on the catalyst’s surface later.


  • Can cleanse pesticides on veggies/fruits
  • Can remove 0.001-micron airborne particles
  • Good at eliminating germs and preventing their development


  • Overall performance deteriorate gradually upon usage
  • Efficiency relies on UV-light and external factors
  • Replacement is costly

5. Air Ionizer

Air Ionizer

Air ionization does not use filters to improve indoor air quality. An air ionizer core generator generates and spreads millions of negative ions to attract positive ions.

Then particles will increase weight and fall on the ground, wall, and so on instead of flying in the air. Therefore, an air ionizer should be combined with other types of air purifiers to remove dropped contaminants completely.


  • Generate negative ions that are good for both human health and airborne particles reduction
  • Not depend on filter hence no replacement filter required
  • Produce negligible ozone


  • Only bring airborne particles down but not destroy them
  • Ineffective against gaseous pollutants

6. Electrostatic precipitators

Electrostatic precipitators

Electrostatic precipitators utilize the same ionization method as an Ion generator. Nonetheless, they feature extra collector plates so that users do not need to clean their houses to completely get rid of particles removed from the air.

Via an induced electrostatic charge, these machines spread a massive amount of negatively charged ions into the residential air. These negative ions will combine with positive-ion particles and fall on a flat charged plate.


  • Generate negative ions good for both human health and airborne particles reduction
  • Effective against all kinds of particles
  • Permanent collecting plate without replacement


  • Collector plate needs regular cleaning
  • Ineffective against gaseous pollutants.
  • Generate a lot of ozone that damages human health

7. Ozone generators

An Ozone generator

Ozone generators are intended for removing uncomfortable odors in your house. O3 can react with and destroy molecules of air contaminants quickly.

Yet, as this device produces ozone in great quantity, users will encounter bad health effects. If exposed to an excessive amount of ozone, you are likely to catch asthma, lung irritation, and many other respiratory issues.


  • Destroy airborne pollutants quite effectively
  • Make the air fresher
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  • Unregulated technology which is not used by reputable manufacturers
  • Too much ozone damages human health
  • Ineffective against airborne allergens
  • Reaction with available chemicals may result in more harmful pollutants

What Is The Difference Between An Air Cleaner And An Air Purifier?

Air cleaners often use different air cleaning technologies and a high-capacity fan to clean the air in a wide area. They are meant to collect larger airborne particles such as dust, pet dander, and dead skin.

Meanwhile, air purifiers typically sanitize the air by removing airborne pathogens that cause sickness and allergies such as mold spore, bacteria and viruses. Air purifiers rarely tackle dust and only purify the air over a restricted area.

What to Look for In An Air Purifier?

1. A True HEPA filter is essential

When buying an air purifier, a must-have component is a High Efficiency Particulate Air (HEPA) filter. As we mentioned above, it is capable of removing more than 99.97% of 0.3-micron or larger particles.

HEPA filters are more expensive, but other “HEPA-type” or “HEPA-like” ones, which are not true HEPA filters, will be much less efficient.

2. CADR rating

CADR, which stands for Clean Air Delivery Rate, determines the speed of air cleaning a device can carry out. The more CADR number an air purifier has, the more air change per hour it can make.

Although this factor does not affect the size of particulate matter being eradicated, it is important to make sure the air inside your room is always purified before it is contaminated.

3. Better no ozone

We generally do not recommend cleaning the air by ozone. The United States Environmental Protection Agency warns that ozone can react with other chemicals and even increase indoor air contaminants. Ground-level ozone pollution can result in a lot of serious health effects as we explained above.

4. The noise level

Unlike using an air conditioner, portable air conditioner, window air conditioners, evaporative coolers, infrared heaters, space heaters or anything else in your HVAC system, you might want your air purifiers to work all days as the outdoor air with pollutants can invade your house anytime.

Hence, you had better purchase a quiet model to ensure the air quality around you even when you are sleeping. While most vacuum cleaners emit noise at 80dB, a refrigerator hums at 40dB, humans normally speak at 60dB, your living room should be as quiet as at 50dBA, and your bedroom’s noise should never exceed 30dBA.

You can depend on our description of the types of noise above to find out a model that is silent enough.

Note: Decibels are measured by a logarithmic scale. This means that as the values increase, the difference between them becomes much more significant. For instance, 20dB is not as twice as loud as 10dB, but four times instead.

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Now you know the answer to the question “What is an air purifier”, the difference between air cleaners and air purifiers, and how to buy an air purifier.

Hopefully, our article covers everything you need and is helpful enough. If it still lacks something, please comment below to let us know.

Thanks for reading!

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