An air purifier is a device designed to clean indoor air by removing airborne particles, allergens, gases, and microorganisms. Indoor air pollution is often 2-5 times higher than outdoor levels, according to the EPA. By circulating air through multiple filters or purification stages, an air purifier helps create a cleaner, healthier indoor environment.
Why Are Air Purifiers Needed?
Indoor spaces accumulate common indoor air pollutants from a wide range of everyday sources. Cooking, cleaning, and burning candles or fireplaces release fine particulate matter (PM) and gases into the air, while VOCs from paints, adhesives, and furniture further degrade air quality. Biological contaminants such as mold spores, pet dander, and dust mites can trigger allergies and respiratory irritation, often making indoor air more polluted than outdoor air.
How Do Air Purifiers Work?
Portable Air Purifier
A portable air purifier is a self-contained device designed to clean the air in a single room or a specific area. Unlike whole-home purifiers that connect to an HVAC system, portable air purifiers operate independently. While portable air purifiers come in different sizes and designs, most operate on the same basic principle. A built-in fan draws air through one or more filters, capturing pollutants such as dust, pollen, smoke, and pet dander before releasing cleaner air back into the room.
Whole-Home (HVAC) Air Purifiers
Whole-home air purifiers are integrated directly into your HVAC system to deliver cleaner, healthier air to every room. Unlike portable models that purify air in limited areas, these systems work through your home’s ductwork, filtering air as it circulates throughout your home. They typically combine HEPA filtration, activated carbon, and UV light technology to capture dust, pollen, pet dander, and neutralize odors.
Types of Air Purifiers
Air purifiers use different technologies to target various pollutants. Some rely on mechanical filtration, while others use chemical adsorption or electronic purification. Many modern models combine multiple methods.
- HEPA Filter: A mechanical filter that captures 99.97% of airborne particles as small as 0.3 microns, including dust, pollen, pet dander, and smoke. HEPA filters are the gold standard for removing fine particulate matter.
- Activated Carbon Filter: Uses adsorption to trap gases, odors, and volatile organic compounds (VOCs) from cleaning products, paint, or smoke. Often paired with HEPA filters for complete particle and odor control.
- UV-C Light Purifier: UV-C light purifiers don’t use a physical filter. Instead, they use short-wave ultraviolet light to kill or deactivate germs like bacteria, viruses, and mold by damaging their DNA. They’re often used along with HEPA or carbon filters to both trap particles and disinfect the air.
- Electrostatic Precipitator: Electrostatic precipitators remove particles from the air by giving them an electric charge. The charged particles are then attracted to oppositely charged plates, where they stick and can later be cleaned off.
- Ionizer (Negative Ion Generator): Releases negative ions that attach to positively charged airborne particles, causing them to clump together and fall or be trapped by filters.
- Pleated Media Filter (MERV-rated): These filters have a Minimum Efficiency Reporting Value (MERV) rating, developed by ASHRAE. These filters capture particles between 0.3 and 10 microns. Higher MERV ratings mean better filtration but may restrict airflow if the system isn’t designed for them.
Clean Air Delivery Rate (CADR)
The Clean Air Delivery Rate (CADR) measures the amount of purified air (in cubic feet per minute, or CFM) an air purifier delivers after filtering out pollutants. The higher the CADR, the more efficient the filtration and the cleaner the air it delivers.
As a general guideline, your purifier’s CADR should be about two-thirds of the room’s square footage; for instance, a 240 sq. ft. room would require a CADR of roughly 160 CFM.
While no purifier removes every contaminant, understanding CADR and choosing filters with suitable efficiency ratings, such as MERV, helps ensure you get cleaner, healthier indoor air.
