Pressurization As A Means Of Air Filtration

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: You can also contact them directly at: 800-869-8025.

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Environmental Illness

During the late 70’s and early 80’s people that experienced symptoms that resembled allergies, asthma and disorientation were classified as Environmentally Ill or EI for short. These symptoms were often associated with chemical sensitivities due to various types of building materials, carpet sizing, paints, varnishes and house hold cleaning chemicals. In most cases these materials would off-gas into the living space and the exposure to these chemicals over time would be deemed the cause of Environmental Illness.

One of the challenges with EI was the fact that the medical industry did not recognize this as a real illness. Most general practitioners would discount this illness as nothing more than an over reaction to what patients called strong odors and funny tastes in their mouths. The symptoms were so much like a typical allergic reaction or a cold or the flu that the normal treatment was antibiotics or antihistamines.

The Allergists, on the other hand, did recognize that there were significant symptoms and would treat this problem more aggressively usually by doing skin testing to attempt to isolate the allergen or contaminant to which the patient would react. Over time the Allergists began to identify the causes to in fact be from the living environments of their patients.

Fast forward to today. The building industry, both commercial and residential, have significantly changed the types of chemicals and additives used in the fabrication of most building materials. The green approach has been the mantra from the builders now for the past 10 years. There are better ventilation systems and a better understanding of how to make an office, room or home under positive pressure so that any off-gassing of any chemicals will be pushed out of the living environment while introducing small amounts of fresh, outside filtered air.

Founded in 1985, Pure Air Systems introduced one of the first commercial grade, certified HEPA and Carbon based fan powered air filtration systems for the removal of airborne allergens and pathogens in the residential and commercial markets. Many of the residential customers who purchased the PAS HEPA systems were categorized as environmentally ill. As far as they were concerned their homes were slowly killing them. Since the PAS systems were of all metal construction using only hospital grade components, the units did not contribute any chemicals or off-gassing materials to their environment. In addition to removing airborne particulate and gaseous pollutants, the units were able to introduce small amounts of outside, filtered fresh air to assist in diluting any gases trapped in the living environment.

Working with the EI group was the catalyst for PAS to develop larger and more effective HEPA and Carbon based systems as well as having a much better understanding of how to use the units for both introduction of fresh air and the use of positive pressure. For more information on the complete line of HEPA and Carbon based systems please go to our website at: or follow us on Twitter @pureairsystems. You can also like us on our Facebook page or call us anytime on our toll-free number: 800-869-8025.

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The Future Is The Past

With all of the new digital, hand-held devices coming out on the market on an almost daily basis, it is now possible to connect with anyone, anywhere at voice, text or live video. The speed of change and the speed of adaptation are least for some  people. Yet somehow with all this new found “connection” ability, one feels the need to stop and slow things down a bit just so we can catch our breathe. Are we moving fast because it is necessary or moving fast just because we can?

The home building industry is almost making some significant changes in its construction technology and techniques…except they are going back to the past to make their future brighter. The severe reduction in the values of residential and commercial properties and the lack of potential buyers has created huge challenges for the construction industry. Most people now believe the cost of housing and commercial properties has to come down to a more realistic level. Since property, for the most part, is no longer considered an investment, it now has to offer functionality and sustainability to make it attractive to future buyers.

Architects, designers, building construction managers, building materials manufacturers and environmental designers are now developing building structures that incorporate more of the past than the future. Smaller spaces, using more natural lighting and natural ventilation are now becoming the norm. Use of light weight, strong materials that require no maintenance, painting or resurfacing are now required. Water cisterns and wind and solar power are becoming a bigger part of the self-sustaining portions of the energy packages. Use of special window coverings and coatings can reduce cooling loads by up to 40% or more.

Smaller, yet more functional living space makes for a smaller carbon footprint and requires smaller, more efficient heating and cooling systems. It also means a smaller IAQ system for residential and commercial properties. The newer building designs require ventilation and introduction of fresh, filtered outside air as part of the entire HVAC/IAQ/Ventilation package. This type of process requires a certain kind of filtration technology and at least one company can provide this packaged system.

Pure Air Systems has been manufacturing HEPA and Carbon based, certified, commercial grade, fan powered filtration systems since 1985.  These systems, which include units that range in volume from less than 50 CFM  to 2000 CFM are designed to be used either as stand-alone units or in conjunction with HVAC systems. They are also designed to bring in small amounts of outside, filtered fresh air in addition to filtering all the air in the environment. These units utilize the latest in fan motor technology as they are all ECM motors that use up to 50% less power than standard induction motors.

Pure Air Systems have been incorporated into these new building designs for some time. They are high performance units that have shown to be extremely durable and require minimum maintenance. The all steel fabrication means these units will be around as long as the structure is standing. Sustainability, energy efficiency and performance are the reason engineers, contractors and individuals alike continue to use the PAS systems.

For more information on the complete PAS product line please go to our website at: or follow us on Twitter @pureairsystems or call us on our toll-free number at: 800-869-8025.

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See Water

If at first glance you think I misspelled the title of this blog and it should read “Sea Water” you are incorrect. This is about water in the form of water vapor or condensation that you often see on windows and where ever damp cold air comes in contact with a warm surface. When you “see” water condensing or water dripping from someplace it shouldn’t be you need to find out why.

One of the most common places in a home to find water in the form of condensation in on single pane windows or on walls or surfaces that are inside barriers for outside walls. Condensation forms when the dew point is relatively high…say 60 to 70 degrees and there is a lot of humidity in the air. Since warm air holds moisture better than cold air the condensation issue is usually found in the summer months. Although it can also be an issue in the fall or spring of the year.

One of the challenges with tight homes and office buildings is the limited amount of fresh, outside air that is introduced into the indoor environment. While constantly circulating the air with the HVAC  fan systems does keep the air moving,  it does little to keep the air from getting stagnant or reduce the indoor levels of  CO2. Introducing outside air, even small amounts over time, can be significantly help the occupied areas. However, if the outside air is hot or cool and humid, then the condensation issue can be a problem again.

Some of the newer variable speed drive, high efficiency HVAC systems incorporate a de-humidification function that allows the cooling coils in the air handler to get really cold during the AC cycle prior to turning on the air handler fan. This allows for more removal of the moisture that may be introduced as outside, fresh air through the HVAC unit.

One of the main reasons for minimizing the amount of “indoor” moisture is to reduce or eliminate the potential for mold growth. There are two main “needs” for mold to grow. Water and a food source. Take away either one and you will significantly reduce the chances of mold growing in the indoor environment. So when  you see water in the form of condensation on the windows in your home or office you can be fairly sure that there is moisture forming in other parts of the indoor structure. And….where there is water there is mold.

Pure Air Systems has been making HEPA and Carbon based fan powered air filtration systems since 1985. These units can be attached to  and HVAC system or used as stand-alone units in residential, commercial, institutional or industrial applications. For over 25 years PAS has used their units to introduce small amounts of outside air that is first past through the HEPA units then into the HVAC units. Since the PAS units are mixing small amounts of outside air (usually 50 to 80 CFM ) with large amounts of warm, unfiltered return air ( usually 300 to 800 CFM) there is little chance for moisture to occur.

This process has been used thousands of times since we first introduced the systems and has been very effective at not only cleaning all the air in the homes up to 48 times a day, but provide for some fresh air without the potential for adding moisture or inviting mold growth indoors.

For more information on the complete line of HEPA and Carbon based air filtration systems please go to our website at: Or call us at: 800-869-8025.

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Fresh Air

When we hear the term “fresh air” we often think about being outside next to the ocean feeling the breeze or on top of a mountain breathing the cool, crisp air. Or, when you are stuck indoors in a building or home for long periods of time you might say, “I’m going outside to get some fresh air.” If we really believe the air is better outside, why do we spend so much time indoors? And, more importantly, what is fresh air?

In reality the term “Fresh Air” is really a misnomer. While it is true that air outdoors is not prone to have that “stale air” smell you have indoors due to lack of ventilation, the levels of airborne contaminants and gaseous molecules outdoors is often not any lower. Yes, that is correct. Depending upon where you are outdoors the levels of harmful airborne particulate and gaseous pollutants can be extremely high.

You already know that during the spring and fall of the year various grasses, weeds, trees, etc. produce pollen of all sorts creating significant allergic reactions and health problems. Is this fresh air? You are outside…aren’t you? Or if you are in a downtown area of a large city you can sometimes feel some stinging in you eyes and throat. That’s usually caused by the high levels of gases such as nitrogen oxide, carbon monoxide, sulphur dioxide and hydrocarbons from all the vehicles. Of course you also have all the airborne particulate that is produced by tires grinding dirt into sub-micron particles. So now that we have identified fresh air let’s take a look at the process of using outside air for ventilation and reduction of CO2 in homes and buildings.

Pure Air Systems has been manufacturing HEPA and Carbon based fan powered, commercial grade air filtration systems since 1985. These units were not only designed to filter the air in a room, home or commercial facility but also to concurrently introduce small amounts of outside air and filter that air prior to introducing it to the indoor environment. As we mentioned before, the term fresh air is really a misnomer. Unless the outside air source is filtered prior to mixing with the indoor environment, it is not fresh air.

The PAS product line is capable of introducing high percentages of outside air that is filtered by three different medias. First there is a polyester dual-layer ring panel filter that is designed to take out the larger particles. Second the carbon media removes many of the odors and gases. Third, is the HEPA filter itself which is a certified HEPA rated at 99.99% removal of all particles 0.3 microns and larger. This three stage filtration ensures that any outside air will be in actuality, “Fresh Filtered Air.”

So the next time you hear the term fresh air remember there are levels of fresh air and you need to make sure that you use the right filtration process to ensure you and your family are breathing fresh air.

For more information on this concept and the complete product line offered by PAS please go to our website at: You can also contact us on Facebook and Twitter.

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ASHRAE Ventilation vs PAS Systems


A Discussion on ANSI/ASHRAE Standard 62.2-2007
Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings

OLD STANDARD: The concept of utilizing mechanical ventilation as an effective method for reducing indoor air pollution in homes and small commercial buildings (two – story) has been considered an effective method to ventilate homes and minimize sources of indoor pollution. This concept applies to spaces intended for human occupancy within single-family houses and multifamily structures of three stories or fewer, including manufactured and modular houses.

PREMISE: The use of moderate to high volume self contained air filtration systems to allow for high rates of air filtration to reduce indoor air pollutants in occupied areas while also introducing small amounts outside, filtered fresh air for ventilation in-lieu of large amounts of mechanical ventilation as discussed in the ASHRAE 62.2-2007 standard.


The use of natural ventilation in occupied areas has been around since people lived in caves. It is somewhat interesting to note that the method of ventilation for reduction of indoor air pollutants has not changed much since then.

The use of either natural ventilation ( such as opening up windows, doors or use of gravity vents) or mechanical ventilation such as fans, ducted vents with fans and mechanical HVAC equipment with the ability to introduce outside air have been primary methods of ventilation for years. This method was used for natural conditioning of the air temperature, reduction of stale air (removal of CO2) or reduction and/or removal of airborne pollutants.

There are a number of challenges with using outside air for ventilation. First, if you introduce outside air that is significantly above (hot) or below (cold) the inside ambient temperature you will increase or reduce the temperature and humidity levels in the occupied area and the energy requirements (and equipment costs) to maintain a comfortable temperature and humidity range become excessive. Second, outside air is not really fresh air. In today’s world no matter where you live the amount of contaminants and pollutants in the outside air preclude you from introducing any air from the outside unless it is properly filtered.


Since its inception in 1985, Pure Air Systems HEPA based air filtration units were designed to be used to both filter the air and offer the option of introducing small amounts of outside, filtered fresh air for ventilation and reduction of CO2 and other airborne pollutants. The PAS systems can be used in conjunction with any type of forced air ducted heating/cooling system in the partial by-pass configuration or as stand alone units.

Page 2. Ventilation In Low-Rise Buildings:

The Pure Air Systems filtration units are all fan powered and range in air filtration volume from 350 CFM to 2000 CFM. These units incorporate an ECM energy efficient motor, forward curved blower, prefilter, carbon and certified 99.99% at 0.3 micron HEPA filter. The system is attached to the return air side of the HVAC system and a portion of the return air is brought in through the HEPA system (see image below) and continuously filtered.

A small amount of outside air (usually 50 to 100 CFM) is introduced directly ahead of the PAS unit. This small amount of air is naturally mixed with the ambient air from the return. Since the amount of outside air is much smaller (by percentage) than the amount of ambient air, even with extremely hot or cold outside air, the resultant mixed air temperature that is achieved through the natural mixing process delivered back to the HVAC system has a temperature differential of no more than 5 to 8 degrees F. from ambient. This means the amount of energy required to heat or cool this air back to the required temperature is minimal.


With the new tighter, energy efficient building techniques used today the need for some type of ventilation in occupied areas is necessary. However, with the need to reduce energy costs and meet some of the new LEED building certifications it is more important then ever that alternate methods of introducing outside air for ventilation be considered. The ventilation method utilized by Pure Air Systems is not only more energy efficient but provides a much greater reduction of airborne pollutants and better indoor air quality.

Pure Air Systems
6115 Guion Road
Indianapolis, IN 46254

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