How Do Air Purifiers Work?

Air purifiers are machines that clean the air inside your home or office. They remove harmful particles, allergens, and pollutants from the air so you can breathe easier.

But how exactly do these helpful devices work their air-cleaning magic?

Let’s take a closer look!

The Filtering Process

At their core, most air purifiers work by pulling in air from the room and passing it through filters that trap particles and freshen the air.

Here’s how the basic air filtering process goes:

  1. Air Intake
    The purifier uses a fan to suck in air from the room through vents or grills on the machine.
  2. Particle Capture
    As the air passes through the purifier’s inner filters, particles like dust, pollen, pet dander, smoke, and more get trapped in the filter material.
  3. Clean Air Output
    The now fresher, cleaner air blows out of the purifier and back into the room through a separate vent.
  4. Recirculation
    The cycle repeats as the purifier continually draws in unclean air from the room, filters it, and releases clean air back out.

So in simple terms, air purifiers take in dirty air, filter out the bad stuff, and blow out cleaner, fresher air!

Types of Air Filters

The most important part of any air purifier is the filter(s) inside that do all the real work of cleaning the air. There are a few main types:

HEPA Filters

  • HEPA stands for “high efficiency particulate air”
  • These fine mesh filters can trap extremely tiny particles like smoke, dust mites, and microbes as small as 0.3 microns
  • HEPA filters remove at least 99.97% of particles that pass through
  • Great for allergies, asthma, and reducing indoor air pollution

Activated Carbon Filters

  • Made from a specialized treated carbon material with millions of tiny pores
  • These pores trap and absorb odors, gases, and volatile organic compounds (VOCs) from air
  • Helpful for removing smoke, pet, cooking, and other unpleasant smells
  • Some purifiers have a thin carbon filter layer before the main particle filter


  • These removable mesh filters are the first layer air passes through
  • They catch larger particles like dust, hair, and pet fur before the main filters
  • Helps extend the life of the finer inner filters by removing big debris

Other Filter Types

  • Ion/electrostatic filters give particles an electrical charge so they stick to collector plates
  • UV light filters use ultraviolet radiation to help destroy microbes
  • Purifiers may combine a few types like HEPA and carbon for maximum cleaning power

Filter Replacement

No matter what type, air purifier filters get clogged up over time and need regular replacing:

  • HEPA filters should be changed every 6-12 months in most homes
  • Carbon filters may need changing every 3-12 months
  • Most purifier models have a filter replacement light to remind you when it’s time
  • Using dirty clogged filters makes the purifier much less effective at cleaning air

Room Size Matters

Air purifiers are intended to clean the air in a single room only – they can’t purify the whole house unless you get a really big industrial unit. That’s why it’s super important to match the size of the air purifier to the room dimensions.

Air purifier manufacturers provide size recommendations based on two key factors:

  1. Room Square Footage
    This is simply the length and width of the room in feet multiplied together. For example, a 12ft x 10ft room has 120 square feet of floorspace.
  2. CADR Rating
    CADR stands for “clean air delivery rate.” It measures the volume of filtered air an air purifier can produce on its maximum fan speed, rated for:
  • Smoke
  • Dust
  • Pollen

The higher the CADR rating, the more air the purifier can clean in a given time period.

Manufacturers suggest maximum room sizes based on a purifier’s CADR rating and the desired air cleaning rate. For most homes, 4-6 air changes per hour is recommended.

Using an air purifier that’s too small or underpowered for your room size means it can’t effectively refresh and filter all the air often enough. That allows pollutants and allergens to build up again quickly after the air purifier cycles through.

Other Air Purifier Features

In addition to the core air filtering ability, many air purifiers come with some additional features like:

Air Quality Sensors

These sensors monitor air particles or gases and automatically increase the fan speed when more filtering is needed.

Filter Change Reminders

Lights or alerts let you know when it’s time to check the filter and replace it if needed based on usage time.

Multiple Fan Speeds

Lower speeds make less noise while higher speeds provide better air circulation and faster cleaning.

Sleep Mode

A quiet low fan setting helps reduce noise for nighttime bedroom use while you sleep.

Air Ionizers

These release negative ions that can help clump up particles to improve filtering.

UV Light

Ultraviolet bulbs or lamps are used to destroy bacteria, viruses, and other germs in addition to air filters.

Remote Control

Allows you to adjust settings and control the purifier without having to manually operate the unit.

Smart Features

WiFi connectivity lets you control and monitor the air purifier through a mobile app on your smartphone or device.

Summary: How Air Purifiers Work

To summarize, air purifiers work by:

  1. Using a fan to draw polluted air into the purifier unit through vents
  2. Passing the dirty air through filters that trap harmful particles, allergens, and contaminants
  3. Releasing cleaner, fresher air back out into the room
  4. Continuously recirculating and filtering the air over and over

The key things that affect how well an air purifier cleans the air are:

  • Type of filters used (HEPA for particles, carbon for odors/gases)
  • Unit’s maximum CADR and air cleaning power
  • Matching the air purifier’s size to your room dimensions
  • Proper filter maintenance by replacing them regularly

With the right sized air purifier for your space and filters kept fresh and clean, these machines can significantly reduce indoor air pollution, allergens, odors, and more – allowing you to breathe easier in your home or workplace!