How Does an Air Purifier Clean the Air?

The simple, sleek outside of an air purifier hides a precisely engineered system inside. It steadily pulls air in, leading it through multiple filtration stages, and sends cleaner air back into the room.

Air Intake: The opening that pulls indoor air into the unit, through the front, sides, or a 360° intake system.

Fan: The motor that moves the air, drawing it through the filters and pushing clean air back out.

Filtration System: The core of the purifier: usually three or four filter layers, each targeting a different type of pollutant.

Air Outlet: The vent that releases purified air back into the room, usually from the top of the unit.

If any one of these four parts isn't doing its job, the purifier's overall performance drops with it.

Once you switch on an air purifier, this cycle begins and repeats nonstop. You won't see it happening, but indoor air is constantly moving through several filtration stages.

Air Intake: The fan pulls in the surrounding air, drawing airborne particles, odors, and other pollutants into the filter system.

Pre-Filter: As first line of defense, it catches larger particles like dust, lint, and pet hair to help prevent the main filters from clogging.

HEPA Filter: This high-efficiency filter helps capture the tiny particles you can't see, including PM2.5 fine particles, pollen, and other allergens.

Deodorization Filter: This layer handles gaseous pollutants, adsorbing household odors, cooking smells, and volatile organic compounds (VOCs).

Clean Air Release: After moving through the filtration layers, clean air flows back out into your room.

Real-Time Air Quality Monitoring: Built-in smart sensors constantly monitor indoor air quality, automatically adjusting modes when air quality changes.

Beyond the filtration system, some air purifiers also include additional technologies that help support cleaner and more hygienic indoor air, such as:

UVnano: Uses ultraviolet light to help reduce bacteria on hard-to-clean areas such as the fan blades.

Ionizer: Releases ions that interact with airborne pollutants to help support cleaner indoor air.

Each filter is designed to remove a different type of pollutant. Knowing the job of each filter helps you choose the right purifier and keep it working as it should.

Large particles like pet hair and dust are the first things an air purifier has to deal with. That's where the Pre-Filter comes in. It captures these larger particles before they reach the main filters, helping keep the filtration system running efficiently.

It helps capture:

• Pet hair

• Human hair

• Fabric lint

• Large dust particles

The standard Easy-to-Clean Pre-Filter can be easily taken out, washed with water, and reused, making routine maintenance simple. Keeping the Pre-Filter clean also helps your purifier perform consistently over time.

The HEPA filter is designed to capture the tiny particles that are hardest to see but can have the biggest impact on your indoor air. It helps trap PM2.5, pollen, mold spores, pet dander, and other fine airborne particles.

Have you ever noticed that even after dust has been removed, certain odors still linger? That's because the substances that create odors are gases, not particles. A deodorization filter is designed to help manage these everyday odors and gaseous pollutants, including cooking odors, cigarette smoke, chemicals released from new furniture, ammonia from pet litter boxes, and formaldehyde that can be found in newly built or remodeled homes.

There are two main methods:

• Activated Carbon: Captures odor molecules through microscopic pores. That capacity fades over time, though, so the filter needs replacing regularly.

• Photocatalytic Deodorization: Uses visible light (sunlight, indoor lighting, etc.) to chemically break down odor molecules. It tends to hold its performance longer than activated carbon, which makes it a good fit where you need long-term odor control.

So, if you live with pets or cook frequently, a Photocatalytic Deodorization Filter or an enhanced activated carbon filter may be a better choice.

Room size is one of the most important factors to consider when looking for an air purifier that will get the job done. To help you make the right choice, manufacturers provide a recommended coverage area (also called the clean air area), which indicates the size of the space an air purifier is designed to clean effectively. Since this specification varies by model, choosing a product whose recommended coverage area closely matches your actual room size helps the purifier manage indoor air more efficiently.

The table below provides general examples based on the commonly used guideline in Korea, where the recommended coverage area is approximately 130% of the actual room size. Use it as a general reference when selecting an air purifier for your space.

If a purifier runs all day, noise matters just as much as performance. Planning to put it in a quiet room like a bedroom or study? Check the noise level in both sleep mode and at full airflow. 

The World Health Organization (WHO) recommends keeping steady background noise in the bedroom at 30 dB or lower for comfortable sleeping.¹⁾

Because manufacturers may present noise specifications differently, it's helpful to check both of the following:

• Sleep Mode: An operating mode designed for quieter nighttime use by reducing fan speed and dimming or turning off display lights.

• Maximum Fan Speed: The noise level when the air purifier is operating at its highest airflow setting.

Some products only list the maximum noise level. Checking the noise level in Sleep Mode can provide a better understanding of how quiet the air purifier will be during everyday use.