The majority of most homeowners are not aware that if their HVAC system is not properly balanced, when the heating/cooling fan system comes on the house may be pulling in outside air into their environment. This is referred to as the house being negative. Since your home is not really air tight, anytime the HVAC fan comes on the system will pull air through the returns and push the cooled or heated air our the supply ducts and registers and if there is more return than supply outside air will come in and make up that difference.
This is a significant challenge as the air being pulled in from the outside will contain fine airborne particulate and some gaseous pollutants especially if you are near a road or high traffic area. This airborne dust is usually not captured in any of the air filters that are part of your HVAC system so this particulate matter will usually settle out on your floors, furniture and counter tops.
In 1985 Pure Air Systems was created and it was one of the first companies to offer true fan powered, certified HEPA air filtration systems for the residential market. The first model, 600HS was designed to attach to the return air side of the ducted heating/cooling system and filter a portion of the air in the house constantly when the fan was running. In most cases it can filter all the air in the house 24 to 48 times per day.
One of the other advantages of this system was the inclusion of both a ring panel prefilter and true carbon media filter so removal of fine sub-micron particulate and gaseous pollutants was also accomplished. In addition, it is possible to introduce a small amount of outside air into the 600HS, or whichever PAS unit you are using, and this will fill filter any of the air coming into the house and help to maintain a more balance house pressure while still cleaning all the air in the house. And because this small amount of outside air is being introduced prior to the HVAC unit. all of it will be both filtered and heated or cooled.
For more information on the complete line of HEPA and Carbon based air filtration systems please go to our newly redesigned website at: http://www.pureairsystems.com or call us on our toll-free number at: 800-869-8025.