For those of you that live in the northern parts of the US, you know that when summer turns to winter, the air gets much drier. The reason is that cold air holds much less moisture than warm air and as a result the cold winter air is much drier. This also means your are shifting your environmental control system from cooling (removal of moisture and cooling the air) to heating ( heating the air).

When you heat the air using your forced air ducted heating/cooling system you remove what little moisture is in the air. The result is a much dryer environment; dry noses and sinuses and the inevitable static build up. The drier air also play havoc with wood furniture.

This warm dry air also increases the levels of airborne particulate since there is no moisture in the air (water molecules) to attach to the dust particles and make them heavier than air. Therefore you are subjected to more dust particles in the winter than in the summer. Add to the fact that windows and doors are seldom opened in the winter, and you have an environment that gets little to no fresh air or outside moisture for months at a time.

One way to minimize this dry air problem is to add some moisture to the indoor air. This is often done by using a humidifier; either attached to the supply side of the HVAC duct system or the use of a portable humidifier. The challenge, however, is to introduce the correct amount of moisture. If you add too much moisture you will get condensation on the windows. It is difficult to maintain the correct humidity levels.

Another way to introduce moist air and maintain a cleaner indoor environment at the same time is to use the whole-house HEPA air filtration systems manufactured by Pure Air Systems. These unit are fan powered and designed to mate to any forced air, ducted heating/cooling system. Not only will these three-stage filtration systems remove harmful airborne particulates and odors and gases but they are also capable of introducing small amounts of outside filtered fresh, moist air.

The 600HS, 1200HS and 2000HS series of HEPA filtration systems have the ability to introduce 50 to 200 cfm of outside air and mix it with the return air and filter it before it is introduced into the HVAC unit. By adding a 6″ or 8″ duct from the outside (preferably from an area just below the roof line) to the selected PAS HEPA unit, you can bring in some of the more moist outside air and increase the moisture in the house naturally.

Even if the outside air temperature is below freezing you are only adding a small amount of air (usually less than 5% of the total HVAC volume) and the cold air is mixed in the HEPA unit with the return air that is also coming into the HEPA unit. The result is an addition of moisture introduced at the ambient air temperature of the home.

For more information on the complete line of Pure Air Systems HEPA based and media based filter systems please go to our website at:

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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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