How Portable Air Purifiers Work

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Types of Portable Air Purifiers

There are hundreds of different models of air purifiers on the market that utilize the methods of air purification described above, either singly or in various combinations.

All air purifiers are designed to reduce particle pollution to varying degrees. And, because many particulates are biological pollutants, these air purifiers are also reducing biological contaminants at the same time.

Some air purifier designs add a very serious focus on the removal of a broad range of common gaseous pollutants and odors or very specific chemical contaminants. This is done by the addition of filters in the air purifier that are specific to the gaseous pollutants to be removed.

Still other designs stress the ability to not just remove (through mechanical filtration) but also to kill biological contaminants with UVC light or incineration. Incoming air is passed through UVC light in order to kill biological contaminants.

In incineration systems, the primary purpose is the destruction and ongoing reduction of biological contaminants with the additional benefit of a modest reduction in levels of harmful particles.

There are also designs that attempt to "do it all", removing particles, gases and biological pollutants with a combination of technologies.

One of the most important concerns in air purification is the removal of very small pollutants from indoor air. The primary industry specification for an air purifier's ability to remove very small particles is known as High Efficiency Particulate Air (HEPA) filtration.

Therefore, the best mechanical air purifiers offer true HEPA filtration for a very high level of retention of small, lung damaging particles. As mentioned above, the ability to filter very small particles is an important specification because of the health hazards of exposure to such particles.

This is also important for allergy sufferers as some of the most potent allergens, such as those found in dust mite feces, are quite small and are best captured by HEPA filtration.

To give you some idea of how small these fine particles are, a human hair is approximately 100 micrometers thick. HEPA filtration is designed to capture 99.97% of particles one-third of one micrometer in size.

Unfortunately, just because an air purifier states that it offers HEPA filtration, all such air purifiers are not created equal. There are a number of issues to take into consideration when selecting a HEPA air purifier. Click here for more information on HEPA filtration and air purifiers. Click here for more information on choosing an air purifier.

Any mechanical filtration air purifier can achieve HEPA filtration. The question is can it filter enough air in order to make a difference in the room. HEPA filtration without sufficient airflow will not make any meaningful improvement in room air because there will not be enough of the room air being filtered.

An excellent specification that combines both airflow through the air purifier and the level of filtration efficiency (the percentage of particles captured) and the particle size is known as Clean Air Delivery Rate (CADR). Find out all about CADR here.

Noise is also a significant factor in air purifiers. If a large, powerful fan is used to move air through dense HEPA filters to produce large volumes of filtered air, the noise can be objectionable.

There is no question that certified HEPA filtration at very good airflows can be accomplished using the basic principles of air movement and mechanical filtration. One manufacturer has accomplished this by incorporating extremely high standards into their air purifiers utilizing their expertise in medical and clean room air filtration systems.

Other manufacturers seek to meet the challenge of very high levels of filtration of large volumes of air by utilizing a variety of combinations of technologies that typically attempt to improve the capture of small particles at higher airflows.

These include charging particles in the incoming airflow just before it enters the filter, typically with a small negative ion generator. Because the particles are given an electrical charge, they "stick" much more easily to the filter.

Manufacturers that use this technique claim that because they are treating the incoming air instead of all the room air there is no need to create an intense field such as ion generators used for air purification do. Even if very small amounts of ozone are a by-product of this process, they react immediately with the filter and do not enter the ambient air, the manufacturer says.

There is no question that this is an effective method of improving filtration, even to HEPA levels, at very good airflows and in units that are also very quiet.

Another method of improving filtration ability is to release negative ions (sometimes negative and positive ions) into the ambient room air. The idea is that these ions will bond with dust and particulate pollutants and form clusters, which will make them easier to remove by the mechanical filter or by water in air washing systems when they are drawn into the air purifier.

Once again, the question concerning this technique is whether or not ozone is released into room air as a by-product of this process.

With an understanding of how air purifiers remove particulate, gaseous and biological pollutants from indoor air it is easier to make sense of the many and varied air purifier designs on the market.

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