HVAC Equipment, Air Filters, HVAC Service

Air Filters: Purpose, Type, and Replacements

Air filters may seem like a simple aspect of heating and cooling systems, but they are essential to the performance and longevity of your equipment.

Air filters clean up both the outdoor fresh air being provided to the building and the air that is recirculated inside to heat and cool the building. This cleaned, filtered air helps keep the HVAC equipment efficient, and most importantly provides clean, fresh air for the occupants of the building.

Air filters are categorized into three basic groups:

Merv chart displaying different types of filters
  • Merv 8 filters, 30-30% efficiency
  • Merv 11 filters, 60-65% efficiency
  • Merv 13 filters, 85-90% efficiency

All of these filters are typically manufactured in a pleated style. They’re made of a soft fabric, formed to look like an accordion, and are supported by a cardboard frame. The accordion design keeps the filter small while providing the utmost surface area.

The higher efficiency the rating, the smaller the dust particles the filter can capture. While this sounds ideal for all applications, there is one thing to consider: the higher efficiency filters also have an increased resistance. For example, a clean Merv 11 filter can have a similar resistance as a dirty Merv 8 filter. You probably would not be able to use a Merv 11 filter at home in your residential furnace. These are best suited for newer commercial buildings with a design focused on better work environments. These types of buildings are using Merv 11 and 13 filters; you would want a Merv 8 for your own home.Air filter

Changing air filters on a regular schedule will reduce HVAC equipment repairs, the need for duct cleaning, and provide a better environment for those inside. No matter the type of air filter, replacing them regularly is the best practice. Typically, changing filters is scheduled for every three months, however some production facilities would benefit from changing their filters monthly or even weekly.


LONG Building Technologies understands the vital importance of air filters to your heating and cooling system, and our HVAC Service team assists customers in maintaining their HVAC equipment, including air filter service. Please reach out if you have any questions on air filters or to see the other ways LONG can help service your HVAC equipment.

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Jeff Ramsey

Jeff is the General Manager of LONG's HVAC Service team in Colorado.