Let’s clear the air about air filters and purifiers.

Austin is unique (and, at times, exasperating) in that it has three distinct pollen seasons. Oak, ash, elm, and pecan trees pollinate from February to early June. Grasses pollinate from March through September. Ragweed and other weeds release pollen from mid-August to early November.

But did you know that indoor air can have levels of certain pollutants up to five times higher than outdoor air? The promise of an air filter is an enticing one: a device designed to cleanse the air in your home, ridding it of impurities like allergens, odors, smoke, dust, and pet dander. In reality, though, not all air purifiers live up to their marketing hype.

We’ll do a deep dive into the components of air filters, the proper use of air purifiers, and how to get the most value from them.


 Air filters

A crucial part of your HVAC system, air filters remove impurities such as dust, pet dander or even bacteria from the air flowing through your vents. Not only does this improve the air quality within your home, but it also protects your HVAC network from damage.

Air filters come in a number of shapes and materials, each with different capabilities and price points:

  • Flat panel: Typically the most affordable type of air filter, traditional flat-panel models have fibers, most commonly fiberglass, stretched over a framework. They’re disposable and easy to install, but they aren’t necessarily the highest quality, allowing many particles to get through.
  • Pleated: Disposable pleated filters use dense screens of cotton or plastic fibers to remove particles from the air. The pleats provide more surface area for filtration and allow the filter to catch more debris. The price point is slightly higher than that of their flat-panel cousins.
  • Electrostatic: Some air filters are electrostatically charged to trap more (and smaller) particles such as pollen, smoke, or bacteria within their screens. They can be flat or pleated, and they can be disposable or washable.
  • Washable: Washable or reusable filters, available in both ­flat-panel and pleated options, can be hosed down with water or vacuumed to remove any ­particle buildup. While more eco-friendly than disposable filters, they will lose their effectiveness over time — usually after a handful of years.
  • High-efficiency particulate air (HEPA): A title endorsed by the Energy Department, a “HEPA” filter consistently removes at least 99.7 percent of particles in the air that are 0.3 microns or larger. This covers all common allergens, from mold and animal dander to dust mites and pollen, along with some small particles from smoke and pollution.

HEPA filters

A HEPA filter is a type of mechanical air filter that works by forcing air through a fine mesh that traps the very smallest of particles. Though most commonly used in commercial settings that require ­extremely clean air, like hospitals and laboratories, HEPA can also be useful for households where people suffer from allergies or have compromised immune systems.

Not all homes can handle super-dense HEPA filters, though. For HVAC systems not strong enough to push air through the restrictive filters, the result will be drastically reduced airflow and efficiency. For that reason, HEPA filters are most commonly used in freestanding air purifiers and vacuum cleaners, instead.

HEPA-equipped air purifiers are small, portable units that work best for a single room, usually the one where you spend most of your time. HEPA-filtered vacuums trap more dust from their exhaust, throwing less dirt and fewer microscopic dust mites back into the room as you vacuum. Some people report improvement in allergy symptoms after using these vacuums.

Filter quality

All air filters are rated for their ability to remove particles from the air. The industry standard is the Minimum Efficiency Reporting Value (MERV), a scale from one to 16 developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers. Weaker filters are assigned lower numbers and stronger ones have higher values.

Another rating method is the Clean Air Delivery Rate (CADR), a scale developed by the Association of Home Appliance Manufacturers (AHAM) and recognized by the FTC and EPA to measure air purifier efficiency. As with MERV, higher numbers equal better overall performance in terms of particle removal. Most filters fall between the 12 CADR and 240 CADR range.

Generally speaking, filters with higher CADR and MERV ratings equal better overall performance in terms of particle removal, making them a smarter choice for families who suffer from allergies, have pets in the home, deal with excessive dust, or want to capture airborne bacteria.

Air purifiers

Air purifiers usually consist of a filter (or multiple filters) and a fan that sucks in and circulates air. As air moves through the filter, pollutants and particles are captured and the clean air is pushed back out into the home.

Air purifiers can indeed neutralize some of the threat posed by air pollution and by indoor activities. But it’s important to note that there’s no such thing as an air filter that completely purifies the air. The best any air cleaner can do is remove small particles that pass through the filter.

How frequently you will have to change filters varies based upon the purifier type and usage. Some filters are reusable and washable, but they require meticulous maintenance, so you don’t usually find them on the most effective air purifiers.

In addition to the purchase price of an air purifier, you should also factor in operating costs and filter replacement costs. Operational costs can easily amount to $50 annually, since you should be running air purifiers near constantly to garner the benefits.


What should I look for in an air purifier?
  • CADR rating. Simply put, this scale measures how many cubic feet of air an air purifier cleans per minute. It goes up to 400-450, depending on the particle size measured, with any value over 300 being considered high efficiency.
  • Size guidelines. For proper efficacy, you need a model designed to work in the room size. Choose a model that is designed for an area larger than the one you are outfitting it for if you want to operate it at a lower, quieter setting.
  • AHAM (Association of Home Appliance Manufacturers)-verified mark. AHAM’s standards are designed to ensure safety, efficiency and performance. While voluntary, most reputable air purifiers have undergone this certification program, which often provides a CADR rating and size guidelines.
  • True HEPA. You can find true HEPA filters in most home improvement stores or online marketplaces. But if you see “HEPA-like” on the label, buyer beware. It could mean anything, but it is not a HEPA-filtered unit.


Other tips

Both the EPA and the American Lung Association recommend air filtration for people with allergies and asthma, but not as a solution by itself. Controlling allergy-causing pollution and ventilation are more important. In fact, in a clean and well-ventilated home, there’s little medical evidence that air filters/purifiers provide much additional relief.

Using a HEPA filter in your home can remove most airborne particles that might make allergies worse. But the particles suspended in air are not the only ones in your home. There are far more in your rugs, bedding, and drapes, and resting on countertops and tabletops, so it’s important to keep these areas clean. That strategy should include:

  • Vacuum frequently.
  • Replace carpets with wood, tile, or vinyl flooring.
  • Keep pets outdoors if you are allergic to pet dander, or at least away from your sleeping area.
  • Change bedding frequently and wash sheets in hot water.
  • Replace draperies and curtains with roll-up shades.
  • Use plastic covers over mattresses and pillows.
  • Use high-efficiency furnace filters.