The reduction/removal of airborne particulate is usually accomplished by the use of air filters or filtration systems. The filters may be installed in a ducted heating/cooling systems return air grill or as a stand alone unit that circulates the air in a specific room or building. These types of filter systems are the most effective as they allow for circulation of the air within the room and while keeping the room temperature and humidity levels constant.

On the other side of the equation is the use of pressurization to reduce particle levels and/or maintain a higher degree of fresh air in a room, building or environment. To pressurize any room or space you simply need to draw in or pull in enough air from an outside source to change the pressure gradient in the room from either negative or static to a positive pressure room. We can all identify with positive or negative pressure as seen when we enter a large building or office and when opening the door the air blows out into your face ( positive pressure) or you have some difficulty opening the door ( as it seems to be pulled away from you) and overcoming negative pressure.  Another way to identify positive or negative pressure in a room is to open the main door about 1″ and take some smoke or a piece of tissue paper and place it at the door opening. If the smoke or paper moves toward the opening the room is negative, if it moves out toward you the room is positive.

The use of positive pressure as a means of filtration or “room cleaning,” has some major drawbacks. First, the air you bring into the room would probably be from an outside source. Although in a large building you could pull air from any space in the building and pressurize the room but that air may be just as dirty as the air in the room you are attempting to clean. Therefore, using an outside air source for pressurization is usually better but is comes with some costs.

Unless you live in a part of the country or world where the daily average temperature is around 70 degrees fahrenheit  and the humidity is 40% or less, bringing in outside air to pressurize a room will substantially alter the temperature and humidity in the pressurized environment.  In order to use pressurization effectively you would need to introduce at least 30% outside air as it relates to the amount of air being heated or cooled in the room.  For example is you have a room that circulates and conditions 600 CFM through its heating/cooling system you would need to introduce at least 180 CFM of outside air to remove some of the  airborne particulates or contaminants.

This process is often used in smoking areas in bars and lounges and in locations where odors, gases or fumes are being generated and dilution by introduction of outside air is the least expensive alternate. The amount of air introduced from the outside would vary depending upon the type of contaminant as just mentioned. It may be that up to 50% dilution is required to effectively reduce the levels of contaminants, however, this large amount of air will displace half the air in the room so some form of vent is needed to allow the fresher air to come into the room and push the contaminated air out of the room. It will also significantly impact the heating/cooling/humidity levels in the room or space.

For more information on pressurization, filtration and alternate methods of contaminant reduction please contact Pure Air Systems at: http://www.pureairsystems.com. You can also contact them directly 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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