Carpe Diem

The first time I actually paid attention to this Latin phrase was when I saw the 1989 movie Dead Poets Society, staring Robin Williams. The term Carpe Diem means “Seize The Day.”  The movie was about boys coming of age in a prep school and their teacher was providing new ideas and ways to think differently about themselves and the world around them. Some of us look at the world through rose colored glasses while many of us look at the world in wonder.

It is in my nature to question everything. While it is easier to sit back and accept what we hear and read, questioning takes energy but also tasks the informer to explain their position. We seldom question information from sources we believe to be credible or from associates who seem to know more about certain issues than we do. We certainly don’ t want to be cynical all the time and yet we get trapped into accepting something based solely on a small amount of information.

Information on product performance is especially susceptible to this problem. Well-known companies with well establish product lines can come out with a new product or service and we immediately accept their “hyped” performance claims simply because of our product loyalty. We will purchase their product and deem it unacceptable only after we have determined over continued use that it just doesn’t meet the performance claims.

Pure Air Systems has been manufacturing commercial grade HEPA air filtration systems since 1985. The acceptance of true HEPA filters for best choice of removing respirable sized airborne contaminants has slowly progressed over the years. For years ASHRAE standards for pleated media filters ranging in efficiencies of 30% to 95% in particle reduction efficiencies were touted as best choice for airborne particle reduction. However, unlike the HEPA filters which actually have an efficiency rating based upon particle size, the ASHRAE standards were based on particle weight not on particle size reduction efficiency.

Over the years a new “MERV” rating system for filter efficiency came into use to even the playing field. These new MERV ratings established a particle size removal rating for each MERV grade of filter based upon the effectiveness of removing a percentage of particles at 0.3 microns in size. Which, by the way, is the particle size standard for HEPA fitlers. They have to have a minimum efficiency of 99.97% reduction of all particles 0.3 microns in size or lager to be considered a true HEPA filter.

Once the new MERV standards were adopted by the filter manufacturers it opened the eyes of the people and companies that use air filters. Like Robin Williams who stood on the desk in his classroom because he wanted to look at the world from a different point of view, the MERV ratings offered buyers a more objective way to evaluate air filters.

You can view the entire line of HEPA and Carbon based air filtration systems manufactured by Pure Air Systems on our website at: Or contact us by phone 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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I’m Positive You Are Negative!

Positive and Negative. Two words that are often used to indicate how someone feels about a certain issue or to describe the particular temperament of an individual as in “he is always so negative.” These two words are also used in the math world to indicate whether a particular number is positive or negative. But, for the purposes of this blog, we will use these two words to discuss the physical relationship of positive and negative pressures as they relate to heating/cooling systems and mechanical air filters .

When people think about air filters they normally associate them with the one they have in their heating/cooling ( HVAC) system. They need to be replaced about every 3 months or so as they get dirty and can create some air flow problems in the HVAC system. Most people are unaware of the fact that air flow through the HVAC system is affected by a number of variables.

In order to move air through an HVAC system requires a motor powered fan system. The size of the motor, in horsepower, is dependent upon the size of the system. For the most part, there are four sizes; 1/3,  1/2, 3/4 and 1 HP. The fan/motor assembly has to have enough power to move hot or cold air ( and cold air is heavier so it requires more power to move the same amount of air ) through a series of supply and return air ducts and grills as well as through the HVAC filter. Most motors are now multi-speed or ECM digitally controlled motors that automatically adjust speed to fit the air temperature and pre-determined comfort levels for the home.

The fan/motor assemblies have to both pull the air from the return air ductwork, pull the air through the air filter and push the air through the burner or condensing coil and supply side ductwork. The pressure to do this is measured in inches of water. For example, a 1200 CFM 3 ton HVAC system would use a 1/2 HP motor and the total system static, less the air filter, would be .5 ” to .7″ of water. This total pressure does not include the use of a standard, throw-away fiberglass furnace filter. The pressure drop or resistance across a minimum duty filter clean is about .2″. For some of the more dense media filters like the 3M Filtrete filters the clean pressure drop can be as high as .4″ to .5″. Even clean these filters already have almost as much negative pressure as the entire HVAC system.

Once these filters or any air filter gets dirty the pressure drop across some filters can reach 1.0″. This means the motor/fan assembly will not be able to pull and/or push enough air through the HVAC unit to adequately heat or cool the home. As the pressure drop increases, unless you add more horsepower, the motor/fan assembly will actually slow down. This is why it is so important to understand the relationship between pressure ( positive and negative ) as it relates to the overall effectiveness of the HVAC unit.

For more information on understanding the adverse affects of filters on air moving devices please go to the “Pure Air University” tab of the following web site.

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When You Renovate Don’t Forget To Ventilate!

Most homeowners will at some point do some remodeling or renovation in their homes. Sometimes it just means painting the walls or adding some shelving. But in many cases the renovations are more dramatic and including adding or tearing down walls and ceilings or adding a room or two.

Whenever you tear down something, paint a wall, cut some lumber, add tile or carpeting you are generating a lot of dust and particulate into the environment. This is inevitable especially when you are removing sheet rock or adding sheet rock and sanding the joints. Cutting wood or flooring also adds a lot of dust into the area. During this part of the renovation you need to be aware of a few things.

First, if you are cutting wood or flooring or sanding sheet rock it is advisable that you cover the return air grills in the affected area and also turn off the HVAC unit. The fine dust generated during the cutting and sanding procedures will find its way into every crevice of the room and if you HVAC unit is running the fine dust will be pulled into the HVAC unit.  Second, you need to open a window or door and place a fan in the opening blowing out the door or window so you are moving some of the fine dust outside, assuming it is not 20 degrees outside. Third, you need to put a new furnace filter in your HVAC unit prior to the renovation and then remove it once you are done. If you are using a HEPA filter system or high end media it is recommended that you remove the HEPA altogether and put a general duty filter in its place during the duration of the renovation.

If you allow the fine dust particles that are generated during the sanding and cutting to get into the supply side of your HVAC system you will have dust blowing out for months. These fine particles are very small and hard to see until they form a layer of dust on a dark surface.  This is why you want to cover the return air grills in your home.

Pure Air Systems has been making HEPA and Carbon based air filtration systems since 1985 and also offers a complete line of furnace and HVAC filters. For more information on the complete line of filters available from PAS as well as information on a wide variety of air pollution issues please go to our website at:

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Burn Candles At Both Ends…But Don’t Burn Them In The House

Candles have bee around for almost as long as man has been on this earth.  They were the very first form of man-made light and were used almost exclusively for many years as the main source of light for houses and buildings. The use of a burning wick and combustible fluid or fuel have improved over the years but the basic candle technology is alive and well in 2010.

Today candles are sold on-line, in candle shops, specialty shops and in most large retail stores. They are scented and many of them come in hand crafted jars with all types of accessories. They provide a nice accent to any room and the scented candles can even be therapeutic. However, they generate a lot of airborne particulate that can be health concern.

Most candles use a standard cotton/wax wick. As the wax burns you have the release of the scented wax used in the candle making process and unburned hydrocarbons or candle soot. You may not notice the carbon soot coming off of the burning candle, but if you hold a piece of clear glass about three inches above the flame  you will eventually see the deposition of carbon or soot on the underside of the glass. This soot is light and easily becomes airborne.

You may notice the candle soot when  you change out the furnace filter in your HVAC system. Ever wonder why the filter was black and not grey? Did you think this was just some really dark dirt? Think again. Much of the dark material on the filter is soot from the candles. The soot becomes airborne, is picked up in the return air grills in your home and then deposited on the filter media.

The unfortunate reality is that much of the carbon soot is extremely small and what you actually see is only about 40% of the soot. The other 60% is too small to see with the naked eye. Some of this sub-micron soot will pass through the furnace filter and end up being deposited on your walls, furniture, floors, etc. It can also be inhaled into your lungs.

Over time this can become a health issue especially if you have severe allergies or respiratory issues. For small children with developing lungs, keeping candles out of their rooms is a good idea. If you use multiple candles the amount of soot is increased. And, candles that are scented are made with special additives to the wax to create the scent. Some of these chemicals are released during the burning of the candle and may create some additional health issues.

Pure Air Systems has been making HEPA and Carbon based air filtration systems since 1985. HEPA filters are capable of removing all of the soot particles produced by the candles. The systems incorporated carbon as well as the HEPA filters and the carbon will remove the gaseous molecules produced from the scented candles. These systems easily attach to the return air side of your heating cooling system.

For more information on the complete line of air filter and filtration systems offered by PAS as well as more information on particulate removal, please go to our website at:

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Delta P Is Not A Fraternity

It is always interesting to see the amount of new technology being developed every day. New computing devices, new 3-D TV’s, new ways to generate energy and yet we understand so little about how these systems actually work. We just assume that when it says to push the red button the system will turn on or off or clicking on this URL will get us to internet nirvana.

This lack of interest in actually knowing “how things work” can be to our detriment. If we don’t know the how or why of a product or system we will make a buying decision based solely on looks and price. For some items this is appropriate. But in many cases some basic research on the product or system is warranted.

Take for example the term “Delta P” or sometimes it is written out using the pyramid symbol with the P following it. This term means pressure differential, pressure drop, resistance in air flow as measured in inches of water and has a lot to do with some products you buy. Specifically air filtration systems and their relationship to their performance and performance of systems they are attached to.

Air filters or any type, style or media make up all create a certain amount of resistance when placed in an enclosed device like a furnace filter in a filter frame or a filter in a fan powered air filtering (air purifying) device.

When the filter is placed on the air entering side of the fan or air moving device it will create some resistance or increase the amount of pressure the fan has to see in order for the air to move through the filtering device. This pressure drop or Delta P is important as it affects both the air flow performance of the heating/cooling system or the filtering device itself.

When you have an air moving device like the fan in the heating/cooling system, the fan/motor assembly is designed to move a certain amount of air ( measured in CFM) at a specific pressure drop or resistance ( measured in inches of water). Let’s say the fan is designed to move 1200 CFM at .5″ of water. This is with a general duty, Walmart fiberglass furnace filter( this filter has a rated pressure drop clean of  .1″).

If you want to install a better, more effective filter in the system, say a MERV 9 or 10 filter, this media has an initial resistance or Delta P of .4″ . This means the furnace fan will have to work harder to pull the air through this filter. If the motor/blower system is only designed to move 1200 CFM at .5″ or .6″ then something has to give. What happens is the furnace fan actually backs down due to the increase in pressure drop and the air flow is reduced. Depending upon the type of fan and motor being used in the HVAC unit the air flow can be reduced by as much as 100 CFM per additional .1″. So if you add .3″ of static that the fan system is not designed for, you can reduce the air flow by 300 CFM.

This air flow reduction is significant in that it now requires the system to run 30% longer to either heat or cool the house due to the additional resistance across the filter. When using filter media such as HEPA filters the initial resistance across these filters can be as high as 1.0″. So it is important to understand the relationship between air flow and Delta P.

For more information on this subject matter and information on the complete line of HEPA filtration systems offered by Pure Air Systems please go to our website at:

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Water: Your Friend – Your Enemy

Water, one of the essentials of life,  is necessary for life to exist; human and all other plant and animal life. We know water as a liquid and we also know water as a vapor as in water vapor or as humidity when the temperature and dew point get close to each other. We use water for everything. It is now being considered a more important product than oil in some parts of the world.

Yet, water can also be your enemy when it finds it’s destructive “dark side” , so to speak. This happens when we have water leaks in the roof; leaking water pipes, water in the basement, too much rain, flooding, etc, etc, etc.

Aside from the structural damage that water can do to any structure, the residual affects, like the development of mold and bacteria, can be significant. When any indoor surface gets wet; be it the walls, carpeting or floors, if all the water is not removed quickly and the surfaces and materials not completely dried, as sure as night follows day, mold will follow.

When water leaks behind a wall or onto a floor surface or into carpeting the sub-surface wood flooring or wood studs behind walls can become wet. Wood will absorb the water and wood takes a long time to dry out. Especially inside the home. Wood is a great food source for mold and the accompanying moisture keeps it growing. Add to the fact that these areas are dark, and you have the perfect breeding ground for mold.

Mold tends to spore once every 15 to 30 days during  its growth cycle and when this happens it releases millions of tiny mold spores which are very light and can become airborne. If the moldy wood source is exposed the mold will eventually get into the entire home and become dispersed through the HVAC system.

To minimize the amount of mold that is airborne in your home you need to make sure your air filters in the HVAC unit are capable of removing small, less than 10 micron in size particles. The filter should be a MERV 8 or higher rated filter and fit very tightly in the air filter frame locate on the return  air side of the HVAC air handler. In addition, you will need to make sure  the water or moisture problem is resolved otherwise the mold problem not go away.

Pure Air Systems has been dealing with mold spore removal since 1985 using its HEPA based air filtration systems that can either be attached to any forced air ducted heating/cooling system or as stand-alone unit. In addition, Pure Air Systems offers a complete line of dual layer polyester ring panel, MERV 8 commercial grade filters that will fit tightly in your HVAC filter frame and effectively reduce the level of airborne mold particles in your home environment.

For more information on our complete line of HEPA and particulate removal air filters go to our



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The Truth About Air Filter Efficiency

It is always interesting to see how companies that manufacture air filters, especially those for the residential market, use images of dust mites, dirt, dander and other graphic photos to illustrate the significance of using their filter if they really want to rid their home of these nasty airborne creatures.

Usually these companies compare the efficiency of their filter against the standard air filter that you use in your heating/cooling system and show how theirs is much more effective in removing these harmful airborne allergens.

For the most part, all of the air filters available from the retail stores are made from similar filter media and have similar efficiencies. Some are pleated, some aren’t, some are washable and reusable and many are not. Almost all of them have a cardboard frame and come is a wide variety of sizes.  And, their prices vary from less than $1.00 each up to $10.oo or more per filter.

When shopping for these filters you will notice that many or most of them now come with a MERV rating label to indicate their overall efficiency.  These MERV ratings (which are an extension of the old ASHRAE ratings) indicate their filtration efficiency in relationship to how well they remove various sizes of airborne particulate.

In truth, what you really want is a filter that removes as much of the less than 5 micron in size particulate but doesn’t have a high resistance so it won’t affect the performance of your HVAC unit. Typically a MERV 7 or 8 rated filter offers the best combination of particulate removal (small particles) with minimal adverse affect on your heating/cooling air flow.

While it may seem that using a filter with a higher MERV rating than 8 would be better, the truth is that as a filter starts to get dirty and gets a layer of dust on the filter surface, the efficiency of the filter actually gets better as the filter loads up.  And, as the filter gets dirtier the pressure drop or resistance across the filter goes up as well.

Therefore, if you start out with a MERV 9 or higher rated filter you will have  a slightly higher efficiency at first but also a higher initial pressure drop as well. And as the filter loads up the pressure drop will increase rapidly and the air flow across the air handler or HVAC system will drop quickly.  This is why using a MERV 9, 10, 11 or higher rated filter usually requires you to change the filter often, usually once a month verses once every three months for a MERV 8 or lower rated filter. And, these higher rated filters are more expensive.

Pure Air Systems offers a line of MERV 8 rated BioPanel dual-layer polyester ring panel filters that are less expensive than the higher rated media filters, fit more tightly in the filter frame, have zero leakage around the filter and have a much higher dust holding capacity with a lower pressure drop or resistance over the the life of the filter.  These commercial grade filters are not available in the retail market but can be purchased directly from the Pure Air Systems website.

For more information on filter efficiency and the BioPanel filters available from PAS go to our website at:



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Remove Dust Mites, Dust & Allergens

The problem of removing or capturing airborne allergens, dust, dust mite feces and other allergy producing particles has been an on-going challenge for homeowners and with good reason. The new housing construction designs are geared more and more toward the “green” building techniques which mean they are much tighter and more energy efficient. These new, tighter homes have little or no fresh air ventilation and, in essence, the home has become a terrarium.

The ability to capture general dust particles, or dust mite feces and other airborne allergens is normally accomplished by the air filter or furnace filter that is located in the HVAC system. Also, the use of portable, fan powered air filter or air purifying devices are often used and can also be helpful.

However, the use of these filtering devices is effective in removing dust and other particles only if they are airborne. Yes! The particles are not pulled off the floor or other surfaces to the filtering devices. They must be airborne.

The best way to ensure that you are removing these particles is to  always have your HVAC fan setting on your thermostat to the Fan On mode. This means the fan is running all the time even if the heating or cooling modes are not operating. Then, whenever you walk through the house or on the carpeting, or dust or vacuum the carpet, the small, sub-micron particles will become airborne and get picked up through the return air vents or drawn into the portable air filtration device.

The dust particles only become airborne for a short period of time; anywhere from 1 minute to 30 minutes depending upon the size of the particle. This is why constant air movement in the home is necessary to keep the environment as dust free as possible. Again, remember that even thought the dust particles are light and tiny, they will remain on any surface until moved or disturbed.

Once these tiny particles are airborne it is important to ensure that they are properly captured or removed. It is important that the furnace filters and portable filtering devices use a commercial grade filtering media or even HEPA filters for absolute capture.

Pure Air Systems offers a line of dual-layer, polyester ring panel filters that are a MERV 8 rated media. These commercial grade furnace filters fit very tightly into the filter frame and eliminate any bypass around the filter, unlike cardboard frame filters with little or no sealing capabilities.

The ability to seal tightly is important since the majority of the particles captured by the filter are less than 5 microns in size. In addition, the dual-layer media has the ability to hold a lot of dust without any appreciable increase in resistance or pressure drop. This means long life with fewer filter changes.

Pure Air Systems also offers a new, high capacity portable HEPA system that is small ( 13″ square by 21″ long) and powerful. This small HEPA unit can produce up to 500 CFM and offers four speeds, one to suit any room or application. This unit comes complete with a prefilter/carbon media filter and a true, certified 99.99% at 0.3 micron HEPA filter.

For more information on these and other air filtration products go to:



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Time To RE-Think Your Furnace Filter System

No matter what type of forced air heating/cooling system you use, all of them require an  air filter of some kind.  While many people believe the primary purpose of the filter is to remove airborne dirt and dust particles to keep the home or office environment cleaner, the fact is the filters  are used primarily to keep the heating/cooling system clean.

All split system HVAC units have a cooling coil for AC and sets of burners for heating located in the main air handler. It is necessary to keep the cooling coils and burners clean and free of dust and dirt or they will not operate properly and become very inefficient. In addition, the air filter is needed to keep the blower wheel ( the device that moves the air) from getting dirty and out of balance. Also the furnace fan and motor are designed to move the air through the system and compensate only for the static pressure or resistance for only these components. The filter can not add much static load to the fan.

It is for these parameters that most furnace air filters are designed and that is why the majority fall under one of two categories; “crappy” and “almost useless”. Yes, they can remove enough of the larger dust and dirt particles to keep the coil and burners clean but No, they are not dense enough to remove the smaller more harmful airborne particles. Making the filters too dense adds too much static load to the HVAC motor and significantly reduces the air flow and this means you heat or cool longer to obtain the desired room air temperature.

While there are a large number of expensive electronic, hybrid electronic or other media type filters available for use with you HVAC unit, for those of you who want to continue to use a simple, inexpensive, throw-away media filter for your furnace there is a better choice.

Pure Air Systems offers a dual-layer, polyester, ring panel filter that is commercial grade and fits tightly in the filter frame, holds a large amount of dust and dirt, collects particles as small as 3 microns and adds very little resistance or static pressure to the HVAC  blower/motor assembly.  These filters are easy to change and have an unlimited shelf life.

In addition, Pure Air Systems offers a line of filters using the same ring panel design with polyester media on one side and carbon media on the other side. These filters are great for both removing airborne particulate as well as odors and gases.

For more information on these filters and the other filter systems offered by Pure Air Systems go to our website at:

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