In a few areas of the US the weather is mild enough that one can open the windows and allow some air to enter the house from the outside most of the year. For the rest of us opening the windows is only an option for a few weeks out of the year as the heat, humidity and cold temperatures limit our ability to add any outside air to the home.
You’ll notice that we use the term “outside” air rather than “fresh” air as most often the outside air entering the home or occupied facility is anything but fresh.
Because of industrial pollution, cars, trucks, farming, construction, grasses, weeds, pollen, decaying matter and a host of other sources, the air outside has a high concentration of small, less than 10 micron, particulate matter and a wide variety of gases and odors generated by auto emissions, pesticides, chemicals, etc.
So, when you open up your windows to let in some “fresh” air to eliminate the “stale” air, you are actually doing a good job of exchanging one problem for another. So, in order to actually introduce fresh air you need to filter the air as it enters the house. Okay, so how do I accomplish this?
Actually this is not difficult to do. Most homes have a ducted, forced air heating/cooling system which moves air throughout the house and normally has a furnace filter or filtering device located on the return air side of the fan section of the unit. This filter keeps the air handler clean by removing dust and dirt from inside the home.
Simply by adding a 6″ or 8″ diameter duct from outside the house and attach it directly into the main return air duct at the air handler section you can introduce as much as 100 to 150 CFM (cubic feet per minute) of outside air and have it all filtered prior to entering the house.
Using this approach allows you to add a much smaller amount of outside air and is more effective than opening up windows. The HVAC fan will move the air throughout the house in a very short period of time and mix it with the existing air. By using just 100 CFM you will add up to 144,000 cubic feet of air in a 24 hour period or enough to change all the air in a medium sized home 1.2 times per day. The more air you add the higher the exchange rate.
Also, adding a small amount of outside air ( 100 CFM) to the return air duct will not affect the conditioned environment of the house. Since most air handlers move 1200 CFM to 2000 CFM, adding 100 CFM of hot, cold or humid outside air is less than 10% of the total volume of air being conditioned.
Pure Air Systems has been using the concept of adding outside filtered fresh air to homes, offices and other occupied areas since it’s beginning in 1985. This concept, used in concert with the HEPA air filtration systems and air filters manufactured by PAS, has been proven to be extremely effective in thousands of applications across the US and Canada.
In fact, Pure Air Systems pioneered the use of adding outside air with the introduction of its 600HS unit in 1985. Since then the concept of adding outside air has been used with all the HS series units. In addition to filtering out the contaminants this concept will, in many cases, actually slightly pressurize the air in the house, office or occupied environment minimizing the entry of outside contaminants as well.
For more information on using outside filtered fresh air go to our website at: www.pureairsystems.com.
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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