Lessons Learned: HVAC and Quarantine
At its 2006 annual meeting, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) held a few different sessions on how to prepare for the next potential pandemic. They also took a look at what was learned from dealing with diseases such as severe acute respiratory syndrome (SARS) and multi-drug-resistant tuberculosis (MDR TB), the latter of which is still a major concern.
CONTROLLING TRANSMISSIONAn audience of HVAC and health care professionals listened intently to Qian Hua, University of Hong Kong, as he described the speed with which SARS traveled in Asia. His presentation, "Airborne/Droplet Transmission of Infectious Diseases," was given during the seminar "Preparing for the Next Pandemic: Controlling Transmission of Infectious Diseases in Hospitals."
How quickly did SARS move? Hua said the first known case was reported in Hong Kong Feb. 21, 2003. By June 1,700 people had become infected. "It is mostly in buildings that these viruses can spread easily among us," Hua said.
Some disease microorganisms are transmitted through the air after they leave a source person, he said. This type of transmission can be controlled through air dilution, at least to some extent, but they can affect larger areas. Droplet-borne transmission is shorter range; think of colds that spread when someone sneezes.
Hua explained how SARS spread from one person in a multi-building, high-rise apartment complex, to several people in other buildings of the complex. The microorganisms from the infected person came from one of his windows and were re-entrained in the outdoor air. The airflow between the buildings, which were constructed in a ring, allowed the infectious air to be carried up by the wind and into the other buildings.
Another outbreak occurred at the Prince of Wales Hospital in Hong Kong - ward 8A to be specific. "Thirteen out of 20 inpatients were infected with SARS in the same ward, and 11 out of 21 patients in an adjoining ward were infected."
Hua noted that suspended ceiling air tightness is critical for infection containment, in addition to general room air tightness. "There is an air leakage problem in the suspended ceiling," he said. Future work needs to link engineering and medicine. "We must work together to solve medical-engineering problems."
THE TB LINKSession Chair Michael Keen, P. Eng., of St. Michael's Hospital, Toronto, commented, "The integrity of our buildings and HVAC can play a big role in controlling transmission. What helped us was the re-emergence of TB in the 1990s," when the industry became more involved with the design of isolation rooms.
He was introducing Sidney Parsons, of CSIR Building and Construction Technology, Silverlakes, Gauteng, South Africa. Parsons presented "A Study of Resistant TB; Full-Scale Experimental Apparatus to Study MDR-TB Transmission."
"This all started in 1996," Parsons said. There was a global drug-resistant TB crisis, and the heaviest concentration of the outbreak was based in South Africa. "One person became infected every second," he said. "There were four million infections annually. Graves had to be dug in trenches," instead of individual plots.
He cited these major challenges:
The main problem in controlling TB transmission is that it isn't measurable until someone actually becomes infected. "It was not possible to determine appropriate infection control intervention unless infectiousness could be measured," Parsons said. "TB organisms cannot be cultured from the air."
REAL GUINEA PIGSParsons said the design team wound up creating a biological model using guinea pigs. The animals, whose response to MDR TB is similar to the human response, were kept in a separate room from noninfected researchers in a special facility.
"The Airborne Infection Research (AIR) facility used state-of-the-art technology to ensure various envelope interventions," to keep the animals' air separate from noninfected humans.
The AIR facility was opened in January 2005, at the HJE Schultz Santa Centre in Witbank, Mpumalanga. The facility involves extraction of infectious air from patient wards, to exposure chambers housing the guinea pigs, "which serve as living quantitative samplers of human-generated TB," according to the South African Medical Research Council. "Fundamental questions about the infectiousness of MDR-TB can be answered by measuring the number of guinea pigs infected over time." Of course, it was necessary to protect the researchers.
According to Parsons, an isolation design was necessary to protect the researchers. It had to include:
"Patients could spend no more than four hours a day outside, in bright sunlight," said Parsons. Location tracking was used for infectious patients to ensure that they were following these rules. Their air was transferred to the guinea pigs.
The team learned something important about the operations and maintenance: "We totally underestimated the operational cost," Parsons said. And when it came to testing and balancing the systems, "We needed to test from the wards to the animal rooms," which they did with good results. "We were able to achieve what we set out to do regarding the HVAC systems.
"MDR TB is highly infectious," Parsons stated. "The efficacy and efficiency of the systems in this facility are now to be evaluated."
QUARANTINE NEEDSAt a forum titled "Quarantine Stations - What is Needed," a participant pointed out that ASHRAE and the HVAC community at-large need to intensify their involvement in finding solutions for a pandemic. "It is real," he said.
"Bird flu and other pandemics will be here."
It was mentioned that quarantine stations themselves offer several opportunities for HVAC professionals.
The first is the ability to ensure correct HVAC operation. Verify that controls are operating as designed. Also, mechanical systems have to be updated regularly, and those updates must be confirmed. "Policies need to be updated every 90 days," a participant said.
Opportunity two is to incorporate ventilation control. "Automatic control systems must work," said an engineer. "You need someone responsible just for temperature and specialty systems."
Finally, opportunity three is providing proper systems maintenance.
Publication date: 07/24/2006