SARS Poses Concerns For HVAC Systems
Severe acute respiratory syndrome (SARS) has recently been reported in Asia, North America, and Europe, including some cases in the United States. According to the Centers for Disease Control and Prevention (CDC), symptoms may include a high fever, headache, an overall feeling of discomfort, and body aches. Some people also experience mild respiratory symptoms. After two to seven days, SARS patients may develop a dry cough and have trouble breathing. The results can be fatal.
The CDC noted that SARS appears to spread “by close person-to-person contact.” According to the CDC, most of the documented cases of SARS have involved people “who cared for or lived with someone with SARS, or had direct contact with infectious material (for example, respiratory secretions) from a person who has SARS.”
The CDC has identified SARS as a previously unidentified coronavirus, and this information could be critically important in the quest to develop diagnostic tests and possible vaccines.
While the CDC and other health organizations continue to look to find ways to combat the virus, the question for the HVACR trade is whether our industry can do anything to retard the spread of SARS.
The Industry Comments
William Coad of McClure Engineering Associates Inc., Atlanta, a board member of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), said, “I don’t believe we’ve figured out how [the virus] is spread yet. Actually, I believe that unattached viruses can be removed with particulate filtration, but I think that we’re a long way from being able to make any recommendations that wouldn’t appear self-serving for someone.”“According to the CDC Web site, the germ is spread similar to a cold, where the virus gets on the droplets of saliva that are misted out when a person coughs,” said Greg Burnett of Dust Free Inc., Royse City, Texas. “If that saliva would make it to the return air handler, then it could be transported through the air conditioning system.
“You get all of these ‘ifs’ stacking up — if this happens, etc. If the virus got up into the air handler and there is a germicidal-type product, it could potentially play a role in slowing the virus down. But it is tough to make a health claim without medical advice.”
Bob Baker of BBJ Environmental Solutions, Tampa, Fla., offered another cautious statement. “At this point in time, any statement or recommendation about SARS related to an EPA-regulated antimicrobial product would be considered ‘false and misleading’ in a legal sense. This is because the exact mode of transmission is currently unknown.”
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Robert Hein of International Environmental Corp., Oklahoma City, Okla., said, “We have not developed a formal position on SARS at this time. Of course, because we manufacture ultraviolet (UVC) lights, which kill microorganisms that might be present in an A/C and/or filtration unit, we will be evaluating the situation much more carefully as we gain more information on the virus itself.
“At this point, I am not sure how long it survives outside of a host. I also have seen differing reports as to the size, which obviously affects the effectiveness of different filtering media. I think it may be way too early be very positive about how A/C systems spread it, or how filtration units may be effective in capturing it.”
One industry expert said it is not too early to begin thinking about preventive measures. Dr. Robert Scheir of Steril-Aire, Ceritos, Calif., stated, “There has never been an identified bacteria or virus, or even mold, that cannot be killed with UVC lighting. The SARS virus is a little-known virus that is seldom seen and has not been specifically studied with respect to UVC. However, UVC is effective against all viruses, and the disease is considered to be airborne.
“Therefore, where you have air conditioning, whether it’s a commercial building with four to five air changes per hour or a hospital environment with 10 to 20 air changes per hour, the circulation of these organisms past the lights should result in better than a 90 percent ‘kill’ per pass.”
Air Filter Recommendations
Presently, standard infection control practices are being recommended for the environmental area in which SARS patients, or probable infected individuals, receive care. According to officials at Camfil Farr, Riverdale, N.J., the environment “should be controlled by using proven methodologies to reduce the probability of exposure. Some items of control include individual respiratory protection, direct source capture using local exhaust ventilation, controlling airflow direction to prevent cross-contamination, dilution, and removal of contaminated air via general ventilation, and air cleaning through air filtration and ultraviolet germicidal irradiation.”According to recommendations from ASHRAE, the United States Department of Health and Human Services (DHHS), the World Health Organization (WHO) and the CDC, the most important factor for infectious disease control is to isolate the patient. “The isolation room should be under negative pressure to prevent droplet nuclei from transferring to other areas of the facility (negative pressure is defined as 0.001 inches water gauge, or 100 feet per minute inward velocity),” noted Camfil Farr.
“The area should also include a ventilation system that reduces droplet nuclei (virus carrier resultant from coughs or sneezes) generated by the patients within the space. Additionally, we should follow procedures as defined by cognizant authorities (local, state, CDC, ASHRAE), ventilation air should meet guidelines as established by the EPA defining ‘clean air,’ and the absolute minimum air change rate of 6 air changes per hour should be used (although 12 is preferred). It is important to note that negative pressure can only be maintained when access is controlled (door closed). Doors should only be opened for entrance and exiting of attending personnel, and closed immediately thereafter.”
The company also notes that when exhausting air from an isolation room, the exhaust criteria defined by the ASHRAE Fundamentals Handbook, Chapter 14, or the ACGIH Industrial Ventilation Manual stipulate that air should never be exhausted less than within 30 feet of inhabitant areas. Air should not be exhausted in the vicinity of walkways or adjacent to windows or openings that may allow reentrance of contaminant.
When infectious isolation rooms cannot be 100 percent exhausted, HEPA filters should be used in duct systems discharging into general ventilation (recirculated air), in ducts for individual room recirculation, in exhaust ducts from booths and enclosures, or in exhaust ducts to remove droplet nuclei from being discharged to other facility areas of habitation, the company states.
According to Camfil Farr, “Air filtration serves an important function in the control of airborne droplet nuclei. A MERV-14 filter, as evaluated by ASHRAE Filter Testing Standard 52.2, will be more than 95 percent efficient on removing droplet nuclei as long as it is given the opportunity to clean the air by moving air through the filter.”
John Hall is business management editor. He can be reached at 248-244-1294, 248-362-0317 (fax), or johnhall@achrnews.com.
Publication date: 05/12/2003