According to the American College of Allergy, Asthma and Immunology (ACAAI) most allergists recommend an air purifier for the home. Air purifiers can be a powerful tool to reduce the presence of indoor allergens. They can also make you less susceptible to triggers. Let’s explore how an air purifier can help, the characteristics you should target and those you should avoid.

Portable vs. Whole-House Air Purification Systems

Portable or room air purifiers provide you relief from allergens in your immediate space. They generally don’t provide enough coverage to keep your home allergen-free. For that, you’ll need a whole-house air purifier. Portable air purifiers are certainly the cheaper and more accessible option up front. Whole-house air purifiers tend to be the better value and more effective long term.


An important concept in air purification is airflow. Air purifiers work by pressurizing air through one or more filter media stages. That process restricts airflow. The amount of air an air purifier moves depends on the cubic feet per minute (CFM) that the blower provides. It also depends on the effectiveness and overall size of the filter media.

Air changes per hour (ACH) is a measure of the total air filtered. An air purifier rated for 2 ACH would turn over all the air in a home twice an hour. Be mindful that this rating is relative to total square footage. If the manufacturer has rated that product for 1,500 square feet, it would be half as effective in a 3,000-square-foot home.

To achieve good indoor air quality (IAQ), the Centers for Disease Control and Prevention (CDC) recommend no less than 4 ACH. Most allergists recommend 6 ACH or higher. You may want to discuss the ideal ACH for your home with your allergist.

Clean air delivery rate (CADR) is an alternative to CFM and ACH commonly used for room air purifiers. It’s important to choose a unit with a CADR that matches the size of the room where you’ll use it. Allergists recommend the two-thirds rule. If you’re choosing an air purifier for a 120-square-foot room, you need an air purifier rated at least 80 CADR.

Ozone-Generating Air Purifiers

There are different approaches to air purification. For allergies, you want mechanical filtration and perhaps absorptive and ultraviolet (UV) filtration. The Environmental Protection Agency (EPA) warns against the use of ozone-generating air purifiers. Ozone is not effective as an air purifier at the levels the federal government allows for residential purposes. It’s also an irritant for people with allergies and asthma. It can act as a trigger and exacerbate symptoms. The EPA also recommends avoiding ionic electrostatic filters. These systems release ions that trap particles against surfaces, but they don’t remove particles. If you disturb them, they can trigger your allergies.

Return-Side vs. Supply-Side Air Filtration

In a central HVAC system, the return side refers to where air enters the system for conditioning. The supply side refers to the ducts and vents that provide the conditioned air to your rooms. Airflow restriction is a much greater concern on the supply side. You’re generally limited there to light mechanical filtration along with absorptive filtration. Most experts recommend opting for a return-side air purifier. It will allow for much more powerful mechanical filtration and a much higher ACH.

HVAC Filter

That’s not to say you can’t benefit from the supply side of your HVAC system. Central HVAC systems do provide some air filtration. Your central system has one or more supply vents that require an air filter. Manufacturers rate their filters using the minimum efficiency reporting value (MERV) rating. The higher the MERV rating, the better the filtration but the worse the airflow. Most modern HVAC systems support up to MERV 13. Investing in that higher-quality filter is worth it, as it will trap pollen and other allergens.

Trapping Large Particulate Matter

Most air purifiers have two forms of mechanical filtration: a prefilter and a high-efficiency particulate air (HEPA) filter. The prefilter traps the largest particles and protects the HEPA filter, which is more expensive. A True HEPA filter will trap 99.97% of all particles down to 0.3 microns in size. A HEPA filter in a system rated for 6 ACH or higher will all but eliminate airborne:

  • Dust
  • Pollen
  • Pet dander
  • Mold spores
  • Fungal spores

Reducing Fine Particulate Matter

True HEPA filters also trap a significant amount of fine particular matter (PM). Fine PM is 2.5 microns in size or smaller. These are the particles associated with ambient air pollution and many cardiovascular and respiratory diseases. While these particles aren’t direct triggers, they are irritants that can make your symptoms worse. You can also opt for a medical-grade HEPA filter. They’re more expensive than true HEPA filters but trap 99.995% of all particles down to 0.1 microns.

Absorptive Filtration

Most of the air purifiers that are good choices for people with allergies will provide absorptive filtration. This is often in the form of an activated carbon stage. Also called activated charcoal, this substance absorbs odors but also volatile organic compounds (VOCs), which can be an allergen. It also absorbs gases and airborne chemicals that can act as an irritant.

UV Filtration

You can opt for an air purifier with a UV stage. Another option is to install UV lamps in your ducts. Both approaches give off a germicidal light that neutralizes bacteria and viruses. People with allergies are more prone to sinus and other respiratory infections, and this helps with that. UV can also neutralize mold, funguses and dust mite eggs.

Other Considerations

Effective allergen control begins with source control, which will only make your air purifier more effective. Dust at least once a week and per EPA recommendations. Choose the houseplants and household products that you bring into your home carefully. If your home lacks ventilation, consider a whole-house fan. It will let you air out the home without introducing pollen and other allergens.

You should also monitor indoor relative humidity (RH). The EPA recommends an RH between 30% and 50%. In warmer months, optimal RH will make it easier to breathe. It will help lower the concentration of allergens in the home and prevent mold and dust mites. In the winter, optimal RH will make your respiratory system less sensitive and you less prone to sinus and other infections.

IAQ Pros Serving Northern and Central New Jersey

If you’d like professional assistance with your IAQ, Pipe Works Services is here to provide it. Our company serves homeowners in Chatham and throughout the neighboring communities. We also provide air sealing and weatherization services and perform home energy audits. Our HVAC technicians install, maintain and repair ductwork and all manner of ductless and ducted heating and cooling systems. That includes furnaces, boilers, heat pumps, air conditioners and mini-splits.

Our plumbers are available for repairs and piping and repiping gas, water and sewer lines. We also hook up appliances and install toilets and other fixtures along with tank and tankless water heaters. Our company also has electricians that upgrade electrical panels and specialize in generators, indoor and outdoor lighting and much more. Contact us today with any questions about these services or to schedule an appointment.

company icon