How to Choose an Air Filter

How do you know which filter is right for you? When you are looking for an air filter for your home, the search may not prove as easy as you expect. There are so many different types from which to choose, and they all have specific purposes. There are many different factors that you should consider when choosing a filter.

Things to consider when choosing a filter:

  • Filter size and model
  • Original vs. aftermarket
  • Home air quality
  • Specific breathing needs
  • Type of filter
  • Filter performance
  • Filter cost and replacement 

Filter Size and Model

Before you begin to choose a specific type of filter, you need know both the size of the filter that fits your air system and the model. It is very important to know the size of your filter because you want your filter to fit; also, you don’t wish to lose money purchasing the wrong filter size. Most filters already have the size printed on the side, but sometimes this is a rounded measurement, and sometimes filters are undercut up to half an inch of the actual size. To be certain that you have the exact measurement, use a measuring tape and measure the height, width, and depth of the filter.

Also, it is important to know the filter model. Knowing the model will allow you to quickly find the filter you need. Also, there are many aftermarket filters that are made to fit specific models, and when looking at a large variety of filters, you need to know which filters fit which models.

Original vs. Aftermarket

There are air filters that are manufactured by specific brands to fit the brands’ models, and these are known as original filters. For example, Aprilaire manufactures original Aprilaire filters for Aprilaire air systems. Aftermarket filters are filters that are manufactured by other companies to fit other brands. For example, offers Accumulaire filters that are manufactured to fit Aprilaire air systems. Aftermarket filters are designed the same as the original filters and offer the same quality, but they come at a cheaper price.

Home Air Quality

One thing to consider when choosing a filter is your home’s air quality. If your home has poor air quality, then you might need to consider a higher quality air filter. Some common factors that lead to lower indoor air quality include:

  • Poor ventilation
  • Tight insulation
  • Smoking
  • Pets
  • Outdoor environment

Some homes are built tightly insulated, which actually increases the amount of indoor air pollution. Poor ventilation of outdoor air leads to the accumulation of indoor air pollutants inside, which means more pressure on your air system as it pulls in air with more particulates. Homes with smokers or homes with pets also contain higher levels of indoor air pollutants and would require a higher quality filter. Another factor to consider is the outdoor environment where you live. If you live near fields or in a big city, for example, the outdoor air seeping into your home will contain higher levels of pollutants. 

Specific Breathing Needs

Some people need a higher quality air filter because of breathing problems. For example, people who suffer from allergies, asthma, bronchitis, sinus problems, and lung problems require a higher quality filter because indoor air pollutants trigger these problems. Also, infants, young children, elderly people, and anyone with existing health problems also benefit from having a higher quality filter. This is definitely something to consider when choosing the filter that is right for you.

Type of Filter 

What type of filter do I need? This is a very important question when choosing a filter. There are many different types of air filters on the market, and most are designed with specific needs in mind. Here are the most common types of filters:

  • Electrostatic filters
  • HEPA filters
  • Carbon filters
  • Pre filters
  • Electronic filters

If you suffer from breathing problems like asthma or allergies, then you probably need an electrostatic filter or a HEPA filter. These filters are specifically designed to remove microscopic allergens like dust mite debris, mold spores, tobacco smoke, pet dander, pollen grains, and bacteria. Electronic filters also trap a large range of microscopic particulates, but they are not the most common, and some of them produce ozone. If you have a problem with odors in your home, then you need a carbon filter, which is designed to reduce odors, gaseous vapors, and chemicals. Pre filters keep your main filters working more efficiently by trapping large particulates that easily clog a filter. 

Filter Performance

Once you decide on the type of filter that you need, the filter’s performance is the next factor to consider.

  • How is the filter rated?
  • What types of particulates does it remove?
  • How efficient is it?

Some air filters are given a MERV rating, some a CADR, to help you determine the quality of the filter’s performance. MERV, which is the Minimum Efficiency Reporting Value, is a number designated by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) to help you compare filters. A CADR is the Clean Air Delivery Rate, which is another rating to help determine filter performance.

Basically, the higher the MERV or the CADR, the more particulates the filter removes and the higher the filter’s efficiency. These ratings are generally given for pleated, electrostatic, or electronic filters. At, because most of our filters are rated by MERV, we recommend at least a MERV 8 for residential use or one with a higher rating for those with breathing problems like asthma or allergies.

HEPA filters are easy to rate. All true HEPA filters are 99.97% efficient at removing microscopic particulates as small as 0.3 microns. They are highly efficient filters, whether for residential, commercial, or industrial use. They provide satisfactory results for those with breathing problems.

Though carbon filters are not given a rating, you want an activated carbon filter or a carbon filter that has been impregnated. Activated carbon is carbon that has been treated with oxygen, which creates tiny pores with high absorption quality. Some carbon filters have been impregnated—for example, with potassium permanganate—to have a greater capturing ability, especially for trapping larger amounts of chemicals and gases.

Filter Cost and Replacement

When choosing a filter, of course there are financial considerations as well. How much does a high quality filter cost? The cost really depends on which filter you choose, whether it is an original or an aftermarket, and the size of the filter. The higher the rating and the larger the size of the filter, the higher the price is going to be. Also, not all filters come in standard sizes; you may not be able to find your exact measurement in the type of filter you want and you may have to have one custom made, in which case the price is usually a bit higher. However, even though high quality filters are a bit more expensive than the cheap fiberglass filters, they are well worth the money, both in providing higher quality air and in keeping your air system working properly.

No matter what type of filter you choose, however, there is one final consideration. Replacement is extremely important for high quality filters. Though some filters are made to last for several years, most filters last about three to five months and must be replaced for optimum performance of the filter. Replacement costs should be considered, as well, but replacement is definitely a necessity for proper functioning of the filter and the efficiency of your air system.