Allergies, Asthma, And The Role Of Hvac

December 6, 2001
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SAN FRANCISCO, CA — The week before the ASHRAE IAQ Conference was held here in early November, a warning was issued of possible terrorist threats against California’s bridges, including San Francisco’s Golden Gate. That warning did not prevent hvac and IAQ professionals from attending the conference. It was a standing-room-only event.

This in itself testifies to the importance of the topic. With public concerns running high over anthrax and other types of biological terrorism, IAQ is a very hot topic.

The conference, however, focused on a more insidious and growing public health problem — asthma — and the role of moisture, mold, fungus, and hvac.

According to the American Lung Association, about 17 million Americans suffer from asthma. It is the leading serious chronic illness of children. “Medical professionals continue to be alarmed and mystified by the dramatic increase in numbers of asthma sufferers over the last decade, during which asthma prevalence has almost doubled,” according to the ALA. “Asthma now kills more than 5,000 Americans each year.”



Why Is It Growing?

According to plenary session speaker Thomas Platts-Mills (University of Virginia), the asthma immune response is triggered by a variety of biological materials, such as grass pollen, animal dander, fungi, cockroach feces, and dust mites. Asthma is preceded by allergic responses; that is, trigger an allergy long enough and a person is more prone to developing the immune-mediated lung inflammation known as asthma.

Platts-Mills theorized that people exposed to cats from an early age have a lower risk of developing asthma. The theory generated debate, including whether people who don’t like cats may have that dislike for a physical reason (they just can’t tolerate cats), and vice versa for people who do like cats.

The reason for the increase in asthma in developed countries, however, seems to be directly related to the increased amount of time people, especially children, spend indoors; and by a decrease in overall lung capacity due to more sedentary lifestyles, again especially in children.

The associations between moisture, allergens, building envelopes, and hvac are too complicated to address here. Hvac itself enters the picture in two ways:

1. Hvac systems need to be designed and maintained so as to decrease the amount of uncontrolled moisture (which allows mold, fungi, and dust mites to breed) they allow to enter occupied spaces.

2. Hvac systems can be designed to trap allergens by means of filtration and other cleaning methods, such as ultraviolet (UV) light.

However, applying more innovative designs isn’t necessarily the best approach, especially when the operation/maintenance of such systems isn’t well understood by the owners/operators. Sometimes it’s hard just to get maintenance performed on standard systems.

IAQ IN SCHOOLS: Best-laid plans

Just as adults spend most of their time in the workplace, children spend many of their hours in school. That’s why “Active Humidity Control and Continuous Ventilation for Improved Air Quality in Schools” was presented at IAQ 2001.

According to presenter Charlene W. Bayer (Georgia Tech Research Institute), the study examined the impact of active humidity control and ventilation on school IAQ.

One particular case had a desiccant system designed to control humidity. Humidity soared when the desiccant system’s fan didn’t run; the system was shut down every weekend to save energy costs, and because that was what the system operators had done with the old (traditional) hvac system.

The researchers also heard complaints that when the desiccant system was on, some classrooms felt hot. When it was shut off, the temperature dropped but humidity rose. Upon examination, the researchers found that a valve was installed incorrectly.

“Training is a huge issue,” she continued. “We could not convince them [the operators] that weekend shutoff is bad for a desiccant system.”

Still, the desiccant system outperformed the existing conventional systems, which operated with lower outdoor air and worse IAQ.

IAQ IN THE HOME: HUMIDITY AND MITES

“A Combined Transient Hygro-thermal and Population Model of House Dust Mites in Beds” focused participants’ attention on the less-than-comforting thought of dust mites in bedding.

Temperature and relative humidity play a critical role in house dust mite (HDM) populations, according to presenter Stephen Pretlove (South Bank University, London, UK). How-ever, they are more affected by humidity than temperature (the lower the humidity, the lower the dust mite movement).

Pretlove and others pointed out that temperature and humidity conditions within bedding or carpeting — prime breeding grounds for dust mites — are different from the ambient air. The top surface of the mattress responds quickly to human occupancy. Relative humidity drops quickly, Pretlove said.

“Preliminary results show that mites tend to move towards areas of high humidity and low temperature.”

There are mattress and pillow covers that help keep dust mite numbers in bedding relatively low. Carpeting is a bigger problem. The ideal solution, according to some, is not to have any wall-to-wall carpeting. However, today’s new homebuyers want carpeting.

That’s why researchers studied “Preventing House Dust Mite Allergens in New Housing.” The paper does not address existing infested homes, said presenter Subrato Chandra (Florida Solar Energy Center, University of Central Florida). “If we’re going to have carpets, let’s see if we can prevent dust mite allergens in these homes.”

According to Chandra, 58% rh is required for dust mite survival; 2 micro grams (mg) of dust is the “magic number” for human allergic response. Humidity levels in the carpeting were key to dust mite survival.

“With central dehumidification, sample homes stayed within acceptable humidity levels,” said Chandra. It climbed sometimes, but was generally well controlled.

“The results of this study show that thorough vacuuming (at least twice weekly with an upright vacuum cleaner with an allergen-trapping dust bag, or once weekly with a central vacuum cleaning system exhausting to outside of the conditioned living area) and a central dehumidification system installed in conjunction with central cooling and heating can maintain dust mite allergens below clinically significant levels in new homes with wall-to-wall carpeting, even in humid climates,” states the paper.

More reports from the IAQ conference will appear in upcoming issues of The News. For more information on ordering proceedings from the conference, contact the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), 1791 Tullie Circle N.E., Atlanta, GA 30329; 404-636-8400; 404-321-5478 (fax); www.ashrae.org (website).

Sidebar: New Staff Hired For ISH NA; Exhibitor List Tops 120

Bob Jarvie has been hired by Messe Frankfurt to assist in the launch of the ISH (International Sanitary and Heating) North America Trade Show and Conference in Toronto, ON, Canada, Oct. 31 to Nov. 1, 2002. ISH NA is an international trade show for air conditioning, heating, plumbing, kitchen and bath, and related industries.

Jarvie will be responsible for booth sales in the hvacr and plumbing segments, as well as provide consulting on the conference sessions. He recently concluded a 14-year stint with the American Supply Association (ASA), including running its ASA Exposition. Jarvie can be reached at 222 Merchandise Mart, Suite 1400, Chicago, IL 60654; 312-464-0090; 312-464-0091 (fax); bjarvie@asa.net (e-mail).

Also, Business News Publishing (BNP) has hired Christin Schrei as special projects advertising manager. Schrei is responsible for advertising sales for the ISH NA show directory, show dailies, and conference brochures. She has 11 years of experience in advertising sales, including the Chicago Tribune and several industry trade magazines. Schrei can be reached at 3150 River Rd., Suite 101, Des Plaines, IL 60018; 847-544-0443; 847-297-3540 (fax); cschrei12@aol.com (e-mail).

According to Messe Frankfurt’s Dirk Ebener, the number of ISH NA exhibitors now exceeds 120. Hydronic heating manufacturer Viessmann Manufacturing is among the recent exhibitor additions. The company has participated in a number of ISH shows in Frankfurt, Germany, and supports the concept in North America, Ebener said.

Several countries have indicated they will participate in ISH NA with a booth or pavilion, added Ebener. To date, they include China, Czech Republic, Germany, Japan, Italy, Spain, Taiwan, and Turkey. Argentina, Australia, Brazil, and Switzerland also have indicated interest.

The Plumbing Contractors of America (PCA) and the Mechanical Contractors Association of America (MCAA) announced they will sponsor ISH NA and encourage their members’ participation. They join the Association of Industry Manufacturers Representatives (AIM/R) as event sponsors. PCA also agreed to hold its annual convention in conjunction with the inaugural show.

ISH NA partners include the ASA, Plumbing-Heating-Cooling Contractors — National Association (PHCC), and Canadian Institute of Plumbing and Heating (CIPH). Each of those associations has agreed to hold their annual conventions in conjunction with ISH NA. The Royal York Hotel has been selected as the ASA headquarters hotel, while the Toronto Sheraton has been selected as the PHCC-NA headquarters hotel.

For more information, contact Dirk Ebener, Messe Frankfurt, Inc., 1600 Parkwood Circle, Suite 515, Atlanta, GA 30339; 770-984-8016; 770-984-8023 (fax); dirk.ebener@usa.messefrankfurt.com (e-mail).

Publication date: 12/10/2001

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