It’s a common acronym and a typical way to purify indoor air, but what exactly is a HEPA filter?
HEPA stands for highly efficient particulate air and is a way of categorizing the quality of air filters built to remove dust, pollen, pet dander, mold, bacteria and other airborne particles from indoor air.
A HEPA-grade filter used in heating, ventilation and air conditioning (HVAC) systems can significantly improve indoor air quality by filtering out small particles of greatest health risk.
Air filters work by trapping pollutants in the fibers of their papery material. A HEPA filter can theoretically capture particles as small as 0.3 microns (for reference a human hair can be between 17 and 180 microns wide.) That means that when placed in a filtration system, HEPA filters can remove 99.97 percent of particulate matter from the air.
While HEPA filters are a very effective way to clean the air, there are other types of filters, including electrostatic filters and electrostatic precipitators, that use a small charge to trap particles.
There is also ionization, a process that charges the particles in a room so that they are attracted to walls, floors and table tops. Some devices that use ionization can attract the charged particles back into the device. Ionization is not recommended by the Environmental Protection Agency (EPA), especially for people with respiratory diseases, as the ionization process can potentially release irritating ozone.
Newer filter systems use ultraviolet (UV) irradiation light to kill germs, notes Jake Loiko, owner of Hawks Mountain Home and Property Services in Springfield, Vermont. “A lot of systems now go UV,” he says. “It’s not just a filter, it kills bacteria, and that’s why they’re getting hugely popular.”
Keep in mind, Loiko says, that UV filters should be used in conjunction with an air filter that takes care of the particles itself. “If you have cat hair flying around, UV won’t take care of that,” he says.
There are many options on the market and understanding the ins and outs of the different air filters can be tricky. We focused on HEPA air filters that can be used for an entire home or HVAC system, using the following selection criteria:
- Non-ozone producing. In some air filtration systems, ozone can be introduced into indoor air at levels “significantly above levels considered harmful to human health,” the report said. EPA.
- Not ionizing. In addition to concerns about ozone production, ionizing air purifiers are not considered as effective by the EPA. “They do not remove gases or odors and may be relatively ineffective at removing large particles such as pollen and house dust allergens,” the statement said. EPA website.
- A MERV score of 8 or higher. MERV stands for Minimum Efficiency Reporting Value, which indicates that a filter can capture larger particles. The higher the MERV rating, the better it is at capturing specific types of particles.
When considering filter options, Loiko recommends making sure your HVAC system has a filter first. “If you don’t have a filter, contact your local HVAC company and have them install a filter rack,” he says.
The most important questions to ask when choosing a filter, Loiko says, is what size filter you need and what you want to filter out. That’s why most of the filters in this list are categorized by the type of pollutants they filter out.
Best filter for the whole house or HVAC system
With an Amazon rating of 4.5 stars out of more than 18,000 reviews and the most economical filter on our list, this synthetic electrostatic filter is popular for a variety of purposes.
With a MERV rating of 13, it can filter out microscopic lint, dust mites, spores, pollen, pet dander, fine dust, smoke, viruses and bacteria. The manufacturer suggests replacing the filter every 60 to 90 days – more often during the summer and winter months.
Best filter for smoke and smog
This is a relatively economical choice and the MERV 8 rating will work well to filter out smoke and smog. The electrostatically charged, pleated synthetic filter can capture 90 percent of airborne particles without affecting airflow, according to the manufacturer.
Instead of ordinary cardboard, it uses industrial beverage cardboard frames for longer life. However, the manufacturer still recommends replacing it every 90 days.
Best filter for pollen
This electrostatic air filter has a MERV rating of 12, making it adequate for common allergens such as mold spores, pollen and pet dander. The real benefit of this filter, and the reason for the slightly higher price tag, is that it can last up to a year before being replaced (depending on usage). That’s because it’s 4 inches thick, but keep that in mind when determining if your system can support a filter of that size.
Best filter for flu season
With a high MERV rating of 13, this 1-inch electrostatic pleated filter can attract and trap microscopic particles. That means it can filter out a wide variety of pollutants, including smoke, cough and sneeze residue, bacteria and viruses. Loiko says you should keep in mind that with the high MERV rating you’ll need to replace this filter more often.
Best Reusable Air Filter
With a 4.5 star rating on Amazon, the K&N is a popular and well-reviewed air filter. With an MERV of 11, it can remove dust, pollen and other particles. Its biggest claim to fame, however, is that it’s washable and reusable, eliminating the need to repeatedly buy disposable filters. (This also makes it a more environmentally conscious choice.)
The filter made from a pleated synthetic material is designed to fit directly into your HVAC filter register and is available in multiple sizes and dimensions. While this filter has the highest price on the list, the ability to wash and reuse it will save you money in the long run.
Best portable air purifiers
If you don’t use your HVAC system very often or you don’t rely on it being completely sealed, you may want a portable, standalone air purifier for your home. Then this air purifier from Medify is a solid and relatively inexpensive option.
Most portable air purifiers come with a clean air delivery rating (CADR). The higher the CADR, the larger the area that will be served. This air purifier has a high CADR value of 950 and can cover 2500 square meters. It can also remove 99.9 percent of particles, including odors, smoke, pet dander, and dust down to 0.1 microns, according to the manufacturer.
Visit local hardware stores
Your local hardware store has most of your basic filters and can be a good place to compare prices and see your options firsthand.
Have the HVAC system checked
Loiko’s biggest tip for homeowners is to make sure your HVAC system is properly maintained. “If your heating system isn’t taped at every seam when it sucks in air, that means it’s sucking air all over the house. So if that’s not all through the filter, you can set up the most efficient filter in the world and it won’t mean anything,” he says.
That’s why he recommends a professional deep-cleaning service to clean ducts and tape off areas that aren’t properly sealed.
All air filters must be cleaned or replaced to operate as promised. “You don’t need a professional to do it,” Loiko says. “Just find your filter, take the housing off and change the filter.”
How often the filter needs to be cleaned or replaced depends on the season or region, but Loiko recommends a minimum of every 3 months. “If you live in a very wooded area, your pollen season will be bad and you may need to replace it more often,” he says. And remember, Loiko says, the higher the efficiency, the more often you have to clean or replace it.
While no single HEPA filter removes all indoor air pollutants, a highly efficient filter, combined with a well-maintained HVAC system, can go a long way. This collection of tips and recommended filters is a good first step towards cleaner indoor air.