How Air Purifier Works? ( Ultimate Guide of 2022 )

Air purifiers cleans the air and helps you eliminate several air pollutants like allergens, toxic fumes, molds, particulates, smoke, etc. Therefore, they have become an essential part of health-conscious households and workplaces.

They effectively reduce the symptoms of allergies, asthma, and other diseases caused by airborne particles. Knowing so many benefits of these, you might be wondering,

How Air Purifier works?

Air purifiers are modern tech gadgets that use complex and sometimes straightforward technology to purify the air. Let’s find out how air purifiers work?

What is CFM?

If you read online reviews of air purifiers or go to purchase an air purifier at any store, you will find the term “CFM” in the specs list. Creating airflow is the underlying phenomenon on which air purifiers work. The air purifiers can suck the polluted air from every corner of the room and release it back after the purification process. For this purpose, they need a powerful fan.

Air purifiers depending upon their size and capacity, come with various fan speeds and settings. Airflow is the primary factor determining the cleaning and working efficiency of a particular air purifier—the unit for measuring airflow in cubic feet per minute or CFM. Powerful air purifiers can achieve a maximum airflow between 300CFM to 400CFM.

What is CADR?

CADR is another deciding factor for the power and efficiency of an air purifier. CADR stands for Clean Air Delivery Rate. As a general rule of thumb higher CADR rating means a powerful air purifier.

However, there are many other factors which may affect the quality and efficiency of an air purifier. For example, an air purifier with a 200CFM CADR rating will work in a 200 sq. ft room, but it will remain ineffective in a 500 sq. ft room.

CADR ratings are given for dust, smoke, and pollen. These three particles are the most commonly found airborne particles and cause asthma, allergies, and other breathing disorders. Association of Home Appliances Manufacturers (AHAM) gives a CADR rating to the air purifiers after testing and approval. However, all the products are not tested and rated by AHAM.

There are two types of air purifiers in general: air purifiers with filters and filterless air purifiers. We shall discuss both of them one by one.

How an air purifier with filters works?

These air purifiers use a high-speed fan and a series of filters. They contain different types of air filters to deal with different types of pollutants.

Pre Filters

Pre-filters are at the first stage of an air-purifying system. They are usually made of durable, washable, and sometimes disposable materials. These filters block the large and coarse air pollutants at the first stage and don’t allow them to enter the expensive and sensitive filters inside the air purifies.

These filters are cheap themselves, but they increase the lifespan of expensive HEPA filters. Coarse and large air pollutants like hair, dust particles, pieces of leaves and paper, can severely damage the internal parts and sensitive filters of an air purifier. These particles block the airflow and reduce the overall performance of an air purifier. Therefore a pre-filter is a straightforward but critical part of an air purifier.

True HEPA Filters

High-Efficiency Particulate Air Filter or True HEPA filters are mechanical filters specially designed to trap fine and invisible air pollutants. They can trap particles as small as 0.3 microns in size or maybe even smaller than this.

A micron is one-millionth part of a meter, so you can imagine how fine the air pollutants are. For example, the size of molds and spores usually range between 3 to 40 micron. Some airborne bacteria could be as small as 0.3 microns.

These filters are made with a highly complex web of delicate fibers. Air pollutants are trapped in these complex fiber mesh. Large particles are trapped in these fibers due to inertial impaction. As they travel through these webs, there is a rapid change in the direction of airflow. As these particles are heavier than the airflow, they are settled down under the action of gravity.

Medium-sized particles are not heavier enough for inertial impaction. These particles are trapped in HEPA filters through interception. Medium-sized particles flow with the air stream and are collected in the trap as they come in contact with any fiber.

The smallest particles are trapped in HEPA filters through a process called diffusion. These articles get diffused in flow-stream, and when they collide with the fibers, they are trapped.

The fourth and last mechanism is sieving. The large particles larger than the spaces between the fibers are grabbed in these spaces when they enter. Moreover, technologically advanced air purifiers feature HEPA filters made of nanofibers. These filters can trap particles as small as 0.003 microns.

HEPA filters have an average life of around 6 months. These files are not washable, and they need to be replaced. Air purifiers have filter indicator lights that tell you whenever you need to replace the filters. Moreover, air purifiers produce a specific noise when they are highly clogged.

Ionic Filters or Ionizers

These filters work on the principle of electrostatic charges. These filters are negatively and positively charged metal plates. Air pollutants could be charged and neutral as well.

Positively charged particles are attracted towards negatively charged plates and vice versa. Moreover, these filters use powerful electric fields, in which high-energy electrons knock and ionize the natural airborne particles and convert them into either negatively or positively charged ions.

Activated Charcoal Filters

Activated Charcoal filters are also called adsorbents. These filters adsorb the airborne particles on their surface because of their charge and size. Remember, they adsorb, not absorb.

Unlike absorption, the particles are not absorbed inside the structure, but they stick to the external surface. These filters are usually installed next to true HEPA filters. These filters remove Volatile Organic Compounds, toxic gases, fumes, and bad odors. These filters are a bed of activated charcoal with properties to absorb fumes and gases on its surface.

Activated carbon is a processed form of carbon having tiny pores in it and a large surface area. Activated carbon with the enhanced surface area has more adsorption sites and tarps the maximum amount of gases, fumes, and volatile organic compounds from the polluted air.

UV Light

UV light essentially sanitizes the air by killing harmful microorganisms like bacteria, molds, and viruses. The UV-C is short-wavelength UV rays that kill bacteria, viruses, and various mold by damaging their DNA.

These filters consist of bulbs that emit light within the UV-C frequency range. As the ambient air is forced to pass through these filters, these UV-C rays either kill or inactivate living organisms by destroying their DNA.

PCO Filters

Photocatalytic oxidation air filtration is a patented technology by NASA. These are the most technologically advanced type of air filters.

A broad septum UV light shines on the titanium dioxide surface and produces hydroxyl ions using water in the air. These negative hydroxyl ions react with organic pollutants and produce carbon dioxide.

How do Filterless Air Purifiers Work?

Filterless air purifiers are also called air sterilizers. They do not tarp or filter any particles and only kill the disease-causing germs. These air purifiers use heat to kill and destroy airborne germs, pet dander, dust mites, molds, etc.

Usually, filterless air purifiers do not use fans. Air enters in air purifiers by natural convection. They use thermodynamic sterilizing technology. Filterless air purifiers have a ceramic core, and they can achieve a maximum temperature of 400 Degree Fahrenheit.

The sterilized air is cooled down to room temperature before being released back into the environment.

Read More: Best Home Air Purifiers | Top-rated Air Purifiers Under 100 Dollars


Where is the best place to put an air purifier?

Air purifiers use high-speed fans for creating airflow, so it should be placed at a spot where the best airflow is possible. The best place in a room is in the center of the room so that air purifiers can suck equal amounts of air from each side of the room.

How long should you run an air purifier per day?

To get the best air quality, you should at least run the air purifier for 12 hours. However, if you live in a highly polluted area or are more concerned with air quality, you can increase the time up to 18 hours.

Do you need an air purifier in every room?

Air purifiers have different capacities, and they do not purify the air of the entire house. However, it is recommended to use an air purifier where you spend most of your time, like a living room, bedroom, etc.

Do air purifiers work for smell?

Yes, air purifiers use HEPA filters and activated carbon filters to absorb odors from the air.

How much area does an air purifier cover?

All air purifiers have different converge. Small air purifiers can only be used in small rooms of around 200 sq. ft. On the other hand, some giant and powerful air purifiers efficiently work in large rooms of around 600 sq. ft.