How Portable Air Purifiers Work

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How Portable Air Purifiers Remove Biological Contaminants from Indoor Air

A wide range of biological pollutants can be removed from indoor air by mechanical HEPA filtration. This includes fairly large biological contaminants such as pollens and pet dander as well as highly potent and very small allergens such as found in dust mite feces.

HEPA filtration also has the ability to capture bacteria and viruses that are 0.3 micrometers in size or larger. In medical applications, mechanical HEPA filtration air purifiers often employ a short wave UV light (UVC) to kill live bacteria and viruses trapped by the filter. This technology is also used in some portable air purifiers.

How Portable Air Purifiers Remove Biological Contaminants with Ultraviolet (UV) Light

Air purifiers that employ short wave UV light (UVC), typically in combination with mechanical or other air purification techniques, are able to kill bacteria, viruses, germs, mold, fungi and spores. There is some question as to how long biological contaminants must be exposed to the UV light in order to be effective. It is known that some viruses are inactivated almost instantly while spores and bacteria may be more resistant.

Nonetheless, UVC light has been successfully used for many decades in a wide variety of demanding applications where microbiological contamination is a concern. These include municipal water purification systems and industrial processes such as microchip manufacturing that require very high purity water.

UVC is also used to sterilize the air in hospitals, operating rooms, pharmaceutical plants, kitchens, meat storage and processing plants, bakeries, breweries, dairies, beverage production facilities, animal labs and so on.

In residential applications, UVC lights are often installed in the HVAC systems ductwork. When utilized in portable air purifiers, it is almost always in combination with mechanical filtration.

How Portable Air Purifiers Remove Biological Contaminants by Incineration

A relatively new technology is the reduction of biological contaminants by incineration. In this system, air is drawn into the air purifier by convection currents. Then, 99.99% of all microorganisms such as dust mite feces, pet dander, fungi, bacteria, viruses, mold spores, mildew, etc. are incinerated at temperatures around 400ºF.

This system does not add any significant heat to the ambient environment and is totally silent and produces no ozone. In fact, testing has shown that in homes where this type of air purifier is used, ozone levels are significantly reduced.

Incineration technology is highly effective on even the smallest microorganisms that are easily carried by air currents into the unit. It does not generate any new emissions and all classes of particles are reduced, with the exception of extremely small particles in the 0.04 micrometers range.

This is most likely the result of the incineration other very small particles. In other words, the overall volume of particles did not increase. Instead, already very small particles were simply broken down into even smaller ones. And given that particulates in the harmful range of 0.04 to 0.3 micrometers decreased overall, the increase in this sub-category is of questionable significance.

And, it should be noted that this overall decrease of very small particles was the result of using a machine that is not designed to remove particulates from indoor air. Particulate reduction is simply an additional benefit to incineration.

What is notable about incineration is that biological contaminants are dramatically reduced and these reductions maintained at extremely low levels in room air. The controlled contaminants are among the most potent allergens and asthma triggers such as dust mite feces, pet dander and pollens and other microbial pollutants that have significant potential for very serious and even life threatening illnesses such as Legionnaire's Disease, etc.

Another benefit to incineration technology is that the unit needs absolutely no maintenance and there are no filters to replace or plates to clean. And, because it draws room air into the unit through convection, there are no fans, making the units completely silent.

How Portable Air Purifiers Remove Biological Contaminants with Ozone

Despite the exuberant marketing claims made by vendors of ozone air purifiers, the U.S. EPA states, "If used at concentrations that do not exceed public health standards, ozone applied to indoor air does not effectively remove viruses, bacteria, mold, or other biological pollutants."

Once again, ozone generators are unsuitable for use as air purifiers.

Other Methods to Reduce Biological Contaminants

Many of the conditions that create biological contamination in indoor air can be eliminated or controlled simply by good housekeeping and maintenance practices.

Controlling excess water and moisture in the home by fixing leaks and seepage, using bathroom vent fans and paying attention to other areas of moisture intrusion and keeping humidity levels between 30% and 60% is especially important and will help control mold, dust mites and cockroaches and inhibit the conditions where microorganisms can flourish.

In addition to having adequate ventilation and good air distribution it is also important to properly maintain and clean all appliances that come into contact with water, as these may become breeding grounds for very serious microorganisms.

Keeping the home clean and controlling dust, especially with a HEPA filtration vacuum cleaner, also contributes to the reduction of biological contamination.

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