The Specter of Chemical Warfare
When a building or home is demolished by an act of terrorism, like the recent tragedies in New York City and Washington, DC, the destruction is almost immediate. While the human suffering is devastating, plans can begin for rebuilding or relocating almost immediately.
But what if a building is not attacked by armament such as bombs or missiles? What if the agent of destruction is harder to detect, yet just as deadly — like toxic chemicals or biological agents? The human suffering can be just as devastating, and the side effects can linger much longer.
Ironically, the systems that hvacr professionals design and build to maintain “quality-of-life” indoor air comfort also have the potential to be misused as vehicles to transport deadly organisms.
“If we assume the organisms are available in sufficient quantities and can be transported, the air delivery systems are one of the most effective ways to spread these deadly organisms,” said Robert Baker, ceo of BBJ Environmental Solutions, Tampa, FL. “We need to spend more money on research — to understand the movement of organisms in the system.
“The problem is, that research costs money. Bioterrorism is with us now, yet the medical community will not stick their necks out to make recommendations because there is not enough information out there. We need to work with Congress to get new wording [stressing research] for appropriations bills, like the Health and Human Services Bill.”
“The big threat is from Anthrax,” said Steve Schulte of Pace Mechanical Inc., Westland, MI. “But there are things the mechanical trade can do to circumvent the threat. Owners need to get involved in the design, construction, and commissioning phases. This should be something we keep in mind for all new construction.”
Protecting The BuildingBaker said that giving contractors access to building systems can be a two-edged sword. “There are numerous people involved in the indoor air quality business — from hvac contractors to maintenance and facility managers to environmental engineers and industrial hygienists,” he said. “Clearly this can lead to a security risk as to who has access and ultimate responsibility for these systems.”
The first line of defense is to restrict access to areas such as mechanical rooms and rooftop units. But that may be easier said than done. Jim Wheeler of Cortez Heating & A/C, Bradenton, FL, knows about that subject from experience.
“I went to a high-rise where I was inspecting a rooftop unit,” Wheeler said. “I asked an employee for the key to the roof and she gave it to me, no questions asked.
“When I got to the roof I noted that there were two large split systems with a penthouse for the air handlers. I went in, opened a metal door and stood there, all alone, between a wall of evaporator coils and a huge centrifugal fan, which supplies air conditioning for all floors of the building.
“If I were a terrorist who wanted to release bacteria, or if I had a drum of chlorine gas, or if I had a bucket of acid and a few sodium cyanide tablets…but I wasn’t.”
Baker stated, “Persons assigned to maintain these systems should be made known to the security personnel, and maintenance should be scheduled and documented.”
Protecting The SystemBeyond the obvious security problem, the question that many building owners and managers are asking is: How do we protect our air-handling systems from chemical warfare? The answer may come from people within the hvacr trade; professionals who test, balance, and maintain healthy airflow within businesses and residences.
The threat of chemical warfare has come at a time when the hvacr industry faces new demands on cleaner, fresher indoor air.
“One unfortunate turn of events is that this threat of biological and chemical terrorism has come at a time when national standards are requiring the introduction of more outdoor air into buildings to improve indoor air quality,” said Wheeler. “This, of course, increases the risks to those in the buildings, since introduction of foreign substances at the air intakes becomes much easier.
“However, even closing intake vents doesn’t eliminate all risks, since most buildings are in a negative pressure without outside-air intakes (because of vent fans), so open doors or windows can also be possible infiltration sources. In addition, anyone who is already inside the building can spread biological weapons by spraying them into any air conditioner air return.”
Schulte said there are solutions, which can come from the familiarity with smoke containment systems.
“Smoke evacuation is a mech-anical mode where automatic controls are triggered by smoke detectors, which start and stop certain fans and open or close dampers,” said Schulte. “The system is also used in concert with a smoke containment system, where smoke and fire are contained by alternating positive and negative pressures on each one of the floors.
“I don’t know why it couldn’t be used to isolate some biological warfare agent.”
ASHRAE’s InvolvementAs building owners and operators look for ways to safeguard occupants, apparently some are closing air intakes to prevent the introduction of hazardous materials into ventilating systems. But according to professionals skilled in indoor environmental control, these well-intentioned actions could also create extensive health problems.
“America’s buildings are amongst the safest in the world; constructed under the protection of a system of codes and standards to assure the utmost protection of safety, comfort, and health,” said William J. Coad, P.E., president of the American Society of Heating, Refrigerating, and Air-Condition-ing Engineers (ASHRAE). “Any steps that result in a reduction of outdoor air ventilation rates or a change in the manner of providing and treating the ventilation air could seriously change the engineered balance of the interior environment. Such changes can result in many of the manifestations of sick building syndrome, causing such maladies as discomfort; eye, nose, and throat irritation; headaches; fatigue; lethargy; loss of productivity; upper respiratory symptoms; skin irritation; or other sickness.”
Americans spend 90% of their time indoors, according to ASHRAE. The association said any deterioration of the indoor environment would create major health problems.
According to ASHRAE, it and other engineering organizations, including the United States Army Corp of Engineers, are currently reevaluating the safety aspects of buildings in light of the terrorist attacks of Sept. 11. Their goal is to provide guidance to building operators and designers for the design and operation of buildings that will make them safer, while not compromising environmental integrity. ASHRAE said the prevention of hazardous material entry into ventilation systems would be studied also. However, it did not state when final findings would be reported.
Wheeler listed some options to kill or trap biological and chemical contaminants inside air conditioning systems.
“Ultraviolet (UV) lights can be extremely effective in destroying bacteria,” he said. If enough of them are installed in air conditioners, they can theoretically destroy 100% of all airborne germs. UV lighting kills germs by destroying their nucleus. How-ever, it is also very hazardous to your eyes, so it should always be located inside the ductwork.
“The best location for disinfecting circulating air is in long, straight areas of return-air ductwork, where the rays can have maximum exposure to the air.”
Wheeler admitted that UV lighting has its drawbacks. For example, there must be enough of them to be effective, the bulbs must be cleaned quarterly, and UV lighting is an expensive solution.
He also made the following suggestions:
• “High-efficiency air filtration is another consideration. A reasonable combination of good filtration and UV lighting can be quite effective in removing most bacteria and viruses.
• “High-efficiency particulate arrestance (HEPA) filters can remove 80% of all bacteria and mold spores from the airstream. But they can only be applied in large a/c systems that are designed for high pressure losses.
• “Electronic air cleaners can also remove more than 80% of all bacteria and mold spores in the air when regularly maintained, and they can be installed in any type of air movement system.
• “Charcoal filters are the only device that I can think of which can remove toxic chemicals from the air, but deep beds of charcoal are required to be effective and they do restrict airflow.”
“Of course, the best protection would be to install a rapid detection system,” said Baker. “It is also important to routinely clean and maintain the hvac system to prevent buildup of organic material on the cooling coils and other moist areas of the system.
“If a small concentration of bacteria managed to reach this area, it can feed on the organic material and amplify to a greater concentration.”
Baker maintained that one of the easiest tasks that contractors can perform is also one of the most routine. “Checking for leakage is very important,” he said. “This is not only good for health and safety reasons, it is also good for energy efficiency.”
Schulte summed up what it will take to make a “terror-proof” system.
“It’s going to take designs involving all electrical, mechanical, fire alarm, and gas-sensing systems.”
It is also going to take educated building owners and educated employees. In other words, hvac customers will be needing a lot of advice and consultation in the coming days.
“Anyone may become a target in the future,”said Wheeler. “It is best for companies’ management to sit down and discuss the hazards and what steps should be adopted for the protection of employees and customers.”