A Guide to HEPA Air Filters in HVAC Systems

It's a commonly used acronym and a typical method for cleaning indoor air, but what exactly is a HEPA filter?

HEPA stands for High Efficiency Particulate Air and is a way of categorizing the quality of air filters designed to remove dust, pollen, pet dander, mold, bacteria and other particles in the air.

A high quality HEPA filter used in heating, ventilation and air conditioning (HVAC) systems can greatly improve indoor air quality by filtering out the small particles that pose the greatest health threat.

Air filters work by trapping pollutants in the fibers of their paper-like material. A HEPA filter can theoretically trap particles as small as 0.3 microns (for reference, a human hair can be between 17 and 180 microns wide ). This means that HEPA filters can remove 99.97% of the particles in a filter system. from the air.

While HEPA filters are a very effective way to purify the air, there are other types of filters, including electrostatic filters and electrostatic precipitators, that use a small charge to trap particles.

There's also ionization, a process by which particles are charged in a room so that they are attracted to walls, floors, and tabletops. Some devices that use ionization can attract charged particles into the device. The Environmental Protection Agency (EPA) does not recommend ionization, especially for people with respiratory illnesses, as potentially irritating ozone can be released during the ionization process.

The new filter systems use ultraviolet (UV) light to kill germs, says Jake Loiko, owner of Hawks Mountain Home and Property Services in Springfield, Vermont. "A lot of systems now go ultraviolet," he says. "It's not just a filter, it kills bacteria, which is why they are becoming extremely popular."

Remember, says Loiko, that UV filters should be used in conjunction with an air filter that will take care of the particles itself. "If you have cat hair that is flying, UV rays can't take care of it," he says.

There are many options on the market and it can be difficult to understand the pros and cons of different air filters. We focus on HEPA air filters that can be used for an entire home or HVAC system and use the following selection criteria:

• It does not produce ozone. In some air filter systems, ozone can be released into the room air in a concentration that is "well above the values ​​applicable to human health," according to the EPA .
• Not ionizing. Aside from concerns about ozone production, the EPA does not find ionizing air purifiers as effective. "They don't remove gases or odors and can be relatively ineffective at removing large particles like pollen and allergens from household dust," the EPA website says.
• A MERV rating of 8 or higher. MERV stands for Minimum Efficiency Report Value, which indicates the ability of a filter to capture larger particles. The higher the MERV index, the better the recording of certain types of particles.

When considering filter options, Loiko recommends first making sure that your HVAC system has a filter. "If you don't have a filter, contact your local HVAC company and ask them to install a filter holder," he says.

The most important questions to ask yourself when choosing a filter, explains Loiko, are the size of the filter you need and what you want to filter. Because of this, most of the filters on this list are classified based on the type of pollutants they are filtering.

The best filter for the whole house or HVAC system

Aerostar pleated air filter 20x20x1

Price: $

With an Amazon rating of 4.5 stars from over 18,000 reviews and the cheapest filter on our list, this synthetic electrostatic filter is popular for a wide variety of uses.

With a MERV rating of 13, it can filter out microscopic lint particles, house dust mites, spores, pollen, pet hair, fine dust, smoke, viruses and bacteria. The manufacturer recommends changing the filter every 60 to 90 days, more frequently in the summer and winter months.

The best filter for smoke and smog

Buy air filter 16x25x4

Price: $$

It's a relatively inexpensive option, and its MERV 8 rating works well for filtering out smoke and smog. According to the manufacturer, the electrostatically charged synthetic pleated filter can hold back 90 percent of the particles suspended in the air without impairing the airflow.

Instead of plain cardboard boxes, use industrial-grade beverage carton frames for durability. However, the manufacturer recommends replacing them every 90 days.

Best pollen filter

Air filter Filtrete Healthy Living 4 inches 20x25x4

Price: $$

This electrostatic air filter has a MERV rating of 12, which makes it more than adequate for common allergens such as mold spores, pollen and pet dander. The real advantage of this filter, and the reason for its slightly higher price, is that it can be used for up to a year before it is replaced (depending on usage). This is because it is 4 inches thick. However, keep this in mind when determining whether your system can support a filter of this size.

The best filter for the flu season

Air filter Filtrete 1900 Premium 20x25x1

Price: $$

With a high MERV rating of 13, this 1 inch pleated electrostatic filter can attract and trap microscopic particles. This means that it can filter out a wide variety of pollutants, including smoke, cough and sneeze debris, bacteria, and viruses. Loiko says keep in mind that if you have the high MERV rating, you will need to replace this filter more often.

The best reusable air filter

K&N 20x20x1 HVAC oven air filter

Price: $$$

With a 4.5-star rating on Amazon, the K&N is a popular and well-rated air filter. With a MERV of 11, you can remove dust, pollen, and other particles. However, its greatest fame is that it is washable and reusable, which saves you from repeatedly buying disposable filters. (This also makes it a greener option.)

The pleated plastic filter fits directly into your HVAC filter register and is available in a variety of sizes and dimensions. While this filter may have 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

Medify MA-112 air purifier with HEPA filter

Price: $$$

If you don't use your HVAC system often, or if it feels like it's not completely sealed, you might want a free-standing, portable air purifier for your home. In that case, this Medify air purifier is a solid and relatively inexpensive option.

Most portable air purifiers have a clean air flow rate (CADR). The higher the CADR, the larger the area that is served. This air purifier has a high CADR rating of 950 and can cover 2500 square feet. It can also remove 99.9% of particles including odors, smoke, pet dander, and dust up to 0.1 micron in size depending on the manufacturer.

Visit local hardware stores

Your local hardware store has most of your basic filters and can be a good place to shop around and see your options firsthand.

Have the HVAC system checked

Loiko's biggest tip for homeowners is to make sure their HVAC system is well maintained. "If your heating system is not sealed at all joints when it is sucked in, you are sucking air out of your entire house. So if everything doesn't go through the filter, you can use the most efficient filter in the world and it won't mean anything, "he says.

He therefore recommends a professional deep cleaning to clean the canals and mask off the areas that are not properly sealed.

All air filters must be cleaned or replaced to function as promised. "You don't need a professional for that," says Loiko. "Just find your filter, remove the case and replace the filter. "

The frequency of cleaning or replacing the filter depends on the season or region, but Loiko recommends at least every 3 months. "If you live in a heavily forested area, your pollen season will be bad and you may need to replace it more often," he says. And remember, says Loiko, the higher the efficiency, the more often you need to clean or replace it.

While no HEPA filter removes all pollutants from indoor air, a highly efficient filter combined with a well-maintained HVAC system can go a long way. This list of recommended tips and filters is a great first step towards cleaner indoor air.

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