Types of Air Purifiers: A Buying Guide

/ Air Filtration & Purification, Equipment Guides & Spotlights / January 22

Clean air can transform any space. In the time of COVID-19, it’s even more important to take the air quality of a home, office or commercial space into serious consideration. Air purifiers not only help clean and sanitize the air around you, but they also have the ability to remove harmful vapors and foul odors. But when looking for the right unit, where do you start? This buying guide breaks down types of air purifiers, filters, ratings and key factors, so you can make the right decision for your home or facility.

Types of Air Purifiers

Before we dive into filters and other key features, it’s important to know the different varieties of air purifiers. Below is a quick a breakdown of solutions on the market.

Standalone Residential Purifiers


This purifier plugs into a wall outlet in any room throughout a home, apartment or dormitory. While used mostly for residential purposes, this unit also can clean air in small offices, restaurant dining areas and rooms under 1,000 sq. ft. with standard 8-foot ceilings.


  • Standard coverage area: 200-800 sq. ft.

  • Common filters: HEPA, carbon, pre-filters, deodorizers

  • Recommended use: Apartments, bedrooms, dorm rooms, living rooms, small offices, small dining areas (i.e. low-occupancy restaurants, taverns, cafeterias)


Browse our selection of Carrier Air Purifiers & Filters.

Standalone Commercial Purifiers


A commercial-grade purifier has the capacity to clean air in a space with more square feet. It also has high-grade filters and filtration stages to combat more tiny contaminants. Depending on room size, ceiling height and average occupancy, you might require more than one unit per room.


  • Standard coverage area: 500-1,500 sq. ft.

  • Common filters: HEPA, carbon, pre-filters, deodorizers, UV light, ionizers

  • Recommended use: Classrooms, healthcare facilities, hospitals, large rooms, offices, restaurants, warehouses


Browse our selection of PuraShield Commercial Air Purifiers & Filters.

HVAC Purifiers


Types of Air Purifiers Buying Guide-HVAC Attached Purifier

  HVAC Purification Filter

Whether it’s a whole home, restaurant or large office, you can always connect a purifier onto an HVAC system. This allows you to improve the air quality in every space using only one solution. However, this option is typically more expensive than a standalone unit and requires special installation.


  • Standard coverage area: 800+ sq. ft.

  • Common filters: HEPA, carbon, pre-filters, deodorizers, UV light, ionizers

  • Recommended use: Hospitals, office complexes, restaurants, schools, warehouses, whole homes


Types of Air Purifier Filters

In order to get the most out of your air purifier, you should consider the types of filtration systems that are available, as not all are quite alike. See what the key differences are between common types of air filters for your purifier. 

HEPA Filtration

Standing for “High Efficiency Particulate Air,” HEPA filters are considered to be top-of-the-line filtration for its ability to filter and trap tiny contaminants and particles. True HEPA filters are capable of removing nearly 98% of microscopic particles, including those measuring 0.3 microns.

These types of air purifier filters are designed to remove particles and contaminants like mold, pollen, pet dander, dust, fungi and smoke. To ensure that your HEPA air purifier works at its most optimal, the filter must be changed regularly to keep the air clean.   

Carbon Filtration

Carbon filters are composed of activated carbon, which traps contaminants, particularly odors, harmful fumes and smoke. Because of their ability to trap smells, gases and other dangerous vapors, carbon filtration is often combined with other forms of filtration.

Ionic Filtration

Ionic filters release charged ions into the air, which attach to contaminants and force them to drop to the floor. To capture these fallen contaminants, some models feature a plate that utilizes an electrostatic charge to pick up the ionized materials and trap them safely.

Types of Air Purifiers Buying Guide-HEPA filter-Pre-filter

Ionic filters are designed to remove contaminants like mold, dust, pollen, fungi, smoke, and have the capability to take care of bacteria, viruses and harmful organic compounds. These filters don’t need to be regularly changed like HEPA filters. However the collection plates do need to be regularly cleaned for optimal usage. 

UV Filtration

Ultra Violet, or UV, filtration utilizes a form of invisible light that neutralizes and cleans the air upon contact. UV filtration in particular kills viruses, bacteria and other germs, creating a sanitary environment. While UV filtration doesn’t affect airborne particles and other contaminants, it is useful in decontaminating a space—especially one that’s shared. 

It’s important to note that UV filtration operates on the UV-C band (UV-A and UV-B especially are the particular spectrums that cause sunburns and other damaging effects), which is safe to humans. Additionally, the UV-emitting technology is contained within the air purifier unit, so it never comes in direct contact with a room. 

Pre-Filtration

As the name implies, a pre-filter is the first step in the total filtration system, taking on large particles so that the main filter isn’t overloaded. Pre-filtration helps prolong the life of the main filter, which also prevents frequent filter changes.

Pre-filters can be cleaned and placed back in the unit, so there’s no need for regular replacements. Additionally, they can also be combined with carbon filters to reduce odors in a room or space.  

Multi-Stage Filtration

Always check the number of filtration stages when choosing between the right type of air purifier. The more stages a unit features, the more protection it offers in your space. Most residential and commercial purifiers feature anywhere from four to eight filtration stages.

Depending on the model, most units use pre-filters in the first stages to trap large dust, hair and dander. The subsequent stages use higher grade filters to trap finer contaminants like mold, allergens, germs and gases. To clean these small particles, many brands use a combination of HEPA, carbon, ionizers, UV, plasma, titanium dioxide (TiO2) and deodorizing filters.

Sizing Considerations

When buying an air purifier, room size is crucial to the unit you’ll choose. Make sure to calculate the square feet of the space when choosing the type of standalone or HVAC purifier. To determine the square feet of the space, do the following:


  • Measure the length and width in feet

  • Multiply the length and width measurements

The total when multiplying length and width equals the total square feet for the space. For example, a room that is 15 ft. in length and 25 ft. in width is 325 sq. ft.

There are two other considerations that should factor into your decision-making process. First, look at the space’s ceiling height. Ceilings that are higher than 8 ft. should use an air purifier for a slightly larger space. Second, an area with connected rooms should use multiple air purifiers or a larger one that factors in the combined square feet of both rooms. If you have rooms exceeding 1,000 sq. ft. or have very high ceilings, two or more standalone units might be required.

Types of Air Purifiers Buying Guide-Air Purifier in Room

Common Air Purifier Ratings

Air purifiers come with a multitude of ratings that communicate their effectiveness and room size requirements that ultimately inform of their performance. These are the most common ratings you might see accompanying your air purifier. 

CADR

The CADR, or Clean Air Delivery Rate, is a rating commonly used on air purifier units that conveys how efficiently they remove contaminants and pollutants, and how far the unit’s reach is in a room. The CADR is independently tested and verified by the Association of Home Appliance Manufacturers (AHAM), who are commissioned by the air purifier manufacturer to procure this rating. This is important to note while shopping for an air purifier, because—while rather common—it’s not entirely ubiquitous. When present, though, it’s a useful comparison tool. 

The ratings appear as a set of three numbers (200/220/190 for example), which indicates the effectiveness of the air purifier at removing contaminants like dust, pollen and tobacco; the bigger the number, the better the unit is at removing those particular particles. To determine the proper CADR for the intended space, AHAM recommends that the rating should at least reach or be equal to 2/3 of the room’s area. For example, an air purifier with a smoke CADR rating of at least 80 can accommodate a room with a square footage of 120. 

Read more about CADR ratings in air purifiers.

ACH

The Air Changes per Hour (ACH) rating is a measurement that informs consumers on how many times the air purifier can convert the air in the room to a clean version every hour. ACH ratings usually come as single numerals followed by an “x,” such as “4x,” “5x,” “6x” and so on. For example, a “4x” rating means that the uncleaned air is taken in through the unit and recycled back four times per hour. The higher the number, the more efficient the unit is at cleaning the air in a room. This rating directly correlates to the maximum space of a room that the air purifier can effectively clean.

Unlike the CADR scale, an ACH rating is standard, and will appear on every air purifier unit. 

Noise Level Rating

One important aspect of air purifiers are their noise levels, which are measured using the designationdB(A).” db(A), or A-weighted decibels, is a measurement that describes the volume level or loudness of air sounds, and is a common measurement seen with air purifiers. Since many air purifiers have fans within the unit, their noise level is marked so that you as a shopper are aware of how quiet the unit is. 

Typical ratings are around 25 dB(A), which is equivalent to a person whispering. The higher the dB(A), the more present or loud the sound is. Many air purifiers usually have a dB(A) in the low- to mid-30s, meaning they are just about whisper-quiet. 

CFMs

Commonly seen in the HVAC space, CFMs (or Cubic Feet per Minute) is a unit of measurement that quantifies the amount of air passing through an air purifier system. As with the other rating systems discussed, the higher the CFM, the faster the air purifier draws in air to clean. 

It also indicates how large of a space it can efficiently operate within. As a rule of thumb, 100 CFM is needed for every 200 sq. ft., so this number directly correlates to the actual amount of space. An air purifier’s CFM rate is an important metric that factors into its CADR, so these two ratings can be seen used together.   

Air Purifier Placement

For standalone air purifiers, placement is crucial for effectiveness. Most units should be placed along a wall in the corner, back or front of the room. However, purifiers with ionizer filters are an exception to this rule. Standalone ionizer units typically work best near the center of the room.

Also, air purifiers need to be unobstructed. A good rule of thumb is to keep them about 3 ft. away from tables, chairs, beds, desks or furniture. Placing them behind bulky items only obstructs proper circulation and air flow.


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