With a few exceptions, most homes in the U.S. use some form of ducted heating/cooling system with air returns and registers located throughout the rooms in the house. The central air handler moves air from the returns back to the cooling and heating coils and then moves it back  into the house to either heat or cool the indoor environment.

On the return air side of the air handler where all the returns merge at one point is where the air filter is located. The filter is designed to remove all the airborne dust and dirt that is in the air. Only dust particles in the air that are pulled into the return air grills will be filtered. If the dust particles are too heavy to be airborne they will remain at rest on a surface and never reach the filter.

The HVAC unit in your home is a balanced system. It is designed so that there is slightly more air moving than returning. This helps to keep the house in a positive pressure mode which eliminates in-leakage of cold or hot air. The balance also includes the ability of the blower/motor to move the air throughout the duct work as well as through the air filter. The air ducts and filter all have a resistance known as Delta P or pressure drop. The higher the pressure drop or static pressure the more powerful a blower/ motor will be required.

If the air pressure is balanced with a clean air filter, once the air filter starts to load up the resistance or pressure drop across the filter ( Delta P ) will increase. If the Blower/Motor is not properly sized as the Delta P increases the air flow across the air handler decreases. Once this takes place the amount of air and amount of airborne dust that is in the air will be significantly reduced and you end up with the air handler running more often just to keep the house cool or warm and more dust in the environment.

This is one reason why you need to change your air filter at least once every 6 months and more often if you live in an urban area. For more information on air filtration and how it works please go to our website at: https://www.pureairsystems.com  or call us on our toll-free number at: 800-869-8025.



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About the Author: Don Musilli

My name is Don Musilli. I started Pure Air Systems in 1985 and then sold it in 2006. I continue to consult for PAS and write their blog and control their Twitter account. I also, on occasion, make changes to the website. The company is now almost 26 years old and has been a major player in offering commercial grade, high performance HEPA and Carbon based filtration systems for the commercial, institutional, industrial and residential markets.

I currently reside in Englewood, Florida where I write blogs and do social media marketing for a number of clients.


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