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Dr. Harriet Burge: Air Cleaners and Other Appliances To Keep Air Clean

I hope you are enjoying the holiday season. The topic of air cleaners and other appliances for keeping air clean in the last issue of the Environmental Reporter has generated quite a bit of interest and discussion. We appreciate the feedback, questions, and additional information that has been provided. Since it is our goal with the Environmental Reporter to try to provide technical information and opinions, we thought we'd share some of these thoughts and opinions with the community in a simple question and answer format as shown below.

Comments from Dr. Harriet Burge

Thanks for taking the time to comment on the Environmental Reporter article. I agree that there are many different modalities for air cleaning. My focus is generally to make indoor environments sufficiently clean and well ventilated, either naturally or using central systems, that separate air cleaning is not necessary. Where this cannot be accomplished or where specific problems exist that mandate their use, room air cleaners can be very useful.

Can air cleaners be used in place of fixing the water problem, normal forms of remediation, or removing the sources of fungal spores?

No. In my opinion, it is clear that water problems must be fixed and any mold growth must be physically removed from the building. Air cleaners serve other purposes and are not a surrogate for fixing the root cause and physically removing areas of mold growth.

Were you aware of the poor performance results for the Ionic Breeze as reported by Consumer Reports?

Yes. Consumer Reports did a Clean Air Delivery Rate Test (CADR). This test measures how fast particles are removed from the air. The Ionic Breeze is not as fast as fan-driven HEPA units and, therefore, will not keep particle levels really low if there is a continuously emitting source. If continuous sources are present, operating the Ionic Breeze will decrease bacterial and fungal particles by about 40%. The units do efficiently remove bacteria (and kill them if you use the UV feature) and fungal spores from the air that passes through them. The air emitted from the units is clean, and they cut the time at least in half for concentrations to reach the 1% level. If somebody needs, or would like 'really clean' air throughout a room, they should use a device with a fan that moves a large volue of air and a filter that is at least equivalent to ASHRAE dust spot 85%. It should be noted that these units must remain on all the time, and they do make noise. I feel it is worth reiterating that there are good data available documenting that people turn off air cleaners because of the noise, even in occupational spaces where the airborne particles are clearly hazardous (e.g., radioactive). One client noted that there are also very quiet HEPA (and near HEPA) filters. They cited Austin Air, and Aerox as good quality HEPA filtration devices that remove VOCs with activated carbon beds from which they have heard good feedback.

Where did the data come from for the efficiency of air cleaners that use electrostatic precipitation?

The data referred to in the article was gathered from research personally performed by me. This research was paid for by Sharper Image (SI) and, no, I do not own any SI stock, nor do I benefit from increased sales of the Ionic Breeze. SI had no input in the protocol, data analysis, or interpretation of the data, which is now being prepared for publication. It is likely that there are many other electrostatic precipitators on the market that function equally well, or even better. The Ionic Breeze was mentioned by name simply because I had first hand knowledge of its efficiency. I am not implying that it is the only device that will work. It is also important to note that the reduction in bioaerosol concentration also depends upon factors such as the size of the room, air currents, activity levels, and whether there are continuing sources of spores. Also note that gravity alone causes a reduction in airborne spore concentrations, subject to constraints such as no continuing sources.

What about ozone?

There were actually several comments related to ozone. The comments ranged from people who had clients who believed that their electrostatic precipitator was creating ozone, to discussions and a few articles assessing its use in cleaning air. For instance the ozone output of the Ionic Breeze has been intensively studied, and should not be high enough to produce odors. If you do use an Ionic Breeze (we can only speak about the device from which we have first hand knowledge), you shouldn't be able to smell the ozone. If you can, something is wrong. If the blades get really dirty, ozone emissions might go up. Otherwise, take the unit back and get a new one or, if you've decided you don't like it, just return it. To the larger question of the general use of ozone in fungal investigations, this is a broad topic and we will address this in a future issue of the Environmental Reporter.

On a personal note, I really appreciate all the comments we have received from this short article. It is this kind of discussion that stimulates all of us to keep on the cutting edge. Please continue to respond to the information we generate. I personally guarantee that we take all comments seriously, and we as a company, have learned a great deal from my contacts with you.

Final comments

Clearly, we all realize that this is a complex topic with a wide variety of opinions. The data continues to be difficult to summarize or to accurately account for the multitude of possible applications. Our hope is that this has at least catalyzed some thought and perhaps even provided some new data for consideration. As always, we welcome your comments and recognize the many thousands of years experience represented by our clients. It is truly the case that we often learn from you.

With best wishes,
Dave Gallup


This article was originally published on December 2004.