Effect of Air Cleaners

As people have become more concerned about indoor air quality, there has been a significant increase in the use of air cleaners to reduce particulate levels.  This has especially been the case with an exponential increase of asthma in children.  The increased use of air cleaners has allowed PGL researchers to look at the impact this has on radon decay products exposures that account for the primary risk associated with elevated radon gas concentrations in a home. 

The good news is that, when properly designed, installed and maintained
 they can significantly reduce radon decay products.

The even better news is that devices now exist that can economically measure radon decay products
to be able to determine the beneficial impact of these devices.

It is important to note that air filters do not reduce radon, but they do reduce radon decay products.  To find a PGL professional who can assist you in determining the efficiency of your air filter in reducing the health risk associated with radon click the button below.  Since this is an emerging field, you may also wish to contact any individual who utilizes E-Perm technology who can arrange to obtain a device for your individual measurement by contacting a PGL professional.

The following pictures and graphs provide information on how well air filtration works in reducing radon decay product risks.  Click on a thumbnail image to enlarge it. 

Air Filter Concept Air circulation created by filter increases plate-out of Radon Decay Products as well as particles to which they are attached.	Stand-Alone Whole House Filters Separate fans and ductwork operate separately from forced air unit or where no forced air system exists.	High Efficiency Filters for Forced Air Units Low pressure drop filters allow them to be added into the return ductwork.
Impact of Whole House Filter System (1) Radon is not affected, but decay products are significnatly reduced.	Impact of Filter System (2)	Impact of Filter System (3) A follow-up measurement in this house indicated radon decay products continued to be controlled.
Effect of Extreme HEPA This is in a laboratory setting where very high circulation rates existed and a very tight HEPA filter was used. This building was slotted for mitigation and interior vacuums were so high (-0.150 in H2O) that several ASD systems would have been needed.	Effect of Air Circulation Much of the radon decay product reduction comes from simple air circulation. Filters enhance reduction and beneficially remove other particulates.	Effect on Unattached Fraction Analogy Although the percentage of the total radon decay products in the small particle range can increase, the overal exposure is reduced. See comment below from the National Academy of Sciences.

During the mid 1990's much of EPA's research budget into new mitigation strategies was reduced.  This occurred at a point in time that air filtration techniques were beginning to be studied, but not completely.  Consequently, some unanswered questions regarding the potential increased dose from the use of air filters in increasing the unattached fraction was placed in some documents and cast doubts on their use.  However, subsequent to this and with better instrumentation, researchers have shown that although the unattached fraction goes up, so does the dose per unit exposure increase, the overall exposure goes down sufficiently to compensate for this. 

This follow-up research was included in the US EPA driven research into risk assessment of waterborne radon and within the section where alternative mitigation techniques were reviewed and updated.

Risk Assessment of Radon in Drinking Water NATIONAL ACADEMY PRESS, Washington, D.C. 1999, Pages 149-151

“From the more recent studies on air cleaners and their effects on exposure to and dose from airborne radon decay products, several important conclusions can be drawn. With the new dosimetric models that more accurately reflect nasal and oral deposition of ultrafine particles, it is extremely unlikely that an air cleaner can reduce exposure and increase dose as suggested by Maher and others (1987), Sextro and others (1986), and Rudnick and others (1983). Thus, there is no reasonable likelihood that the use of an air cleaner will increase the hazards posed by indoor radon.”

 

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Last modified: 06/05/08