Monitoring pathogens with the air conditioner

Posted by () on Sep 01 2011
VERTIC Blog >> Arms Control and Disarmament

Isadora Blachman-Biatch, London

The United States Center for Infectious Disease Research and Policy (CIDRAP) recently conducted a study which highlights potential improvements in national methods of biological pathogen surveillance and detection. The paper is entitled ‘The NYC Native Air Sampling Pilot Project: Using HVAC Filter Data for Urban Biological Incident Characterization’. It shows that commercial heating, ventilation and air-conditioning (HVAC) systems, installed in many modern buildings, could be used to improve existing methods for monitoring the spread of airborne biological agents.
Recently published in the journal Biosecurity and Bioterrorism: Biodefense Strategy, Practice, and Science, CIDRAP argues that modern HVAC could house so-called Native Air Sampling (NAS) equipment. In the event of a dissemination of threatening biological agents, NAS could become a more effective way of measuring the threat than traditional methods. A pilot program conducted in New York found that many private companies were willing to help set up an NAS regime by allowing the use of their HVAC systems.
The United States relies chiefly on a Dedicated Air Sampling (DAS) system, known as BioWatch, to detect potential aerosol disseminations of biological agents. BioWatch conducts laboratory tests to identify biological pathogens found trapped in the filters of air samplers. Any potential biological threat detected by this process triggers a BioWatch Actionable Result (BAR). In such an event, federal guidelines specify that a further round of surface samples must be taken to assess the threat. According to the Congressional Research Service, BioWatch mainly relies on Environmental Protection Agency (EPA) aerosol samplers, mounted on existing EPA air quality monitoring stations.
While BioWatch is good at identifying threats, it is not always effective at determining their magnitude. The air sampling system suffers from several limitations which can produce false-negative results. Firstly, there must be a sufficient quantity of an agent present in a sample to allow correct identification. Wind and rain can act to dilute samples already restricted by uneven pathogen dispersion. Secondly, interference from other substances and errors produced by sampling frequencies can conceal the presence of dangerous substances. According to the Congressional Research Service, the U.S. government’s reliance on surface sampling has made it easy to underestimate the danger and associated risks of particular biohazards.
The benefits of commercial HVAC
Commercial HVAC systems are not so susceptible to these limitations. According to the paper they are ‘primarily used to trap particulate matter including, dust, natural organic debris, and allergens, [including] pollens, mold, spores [and] bacteria’. If a biological threat agent were mixed into the air, sufficient quantities would get stuck in HVAC filters. These quantities could then be used to confirm the potential range of a threat. Unlike equipment used by the EPA, HVAC are widely available, making them ideal for testing the air for contaminant dispersal. Hence, and this is the main benefit, commercial HVACs represent a pre-existing, low-cost network of high-volume air samplers. No further investment is required.
Moreover, HVAC air flow velocities are several orders of magnitude greater than those of passive surface deposition velocities involved in BioWatch surface sampling. Using HVACs would therefore be quicker, more accurate and more effective than DAS since they would collect 2,000 times as much material per cm2.
The CIDRAP study therefore proposed that commercial HVAC might supplement BioWatch equipment. Together, the systems could carry out accurate time-sensitive air sampling. Most importantly, they could help establish the magnitude of the threat.
The New York pilot programme
CIDRAP carried out a pilot project in New York to test the viability of adapting commercial HVAC for biological threat detection. They first conducted local assessments of commercial buildings with HVAC that could be used for NAS. They also met with building managers and property owners to discuss the measures that could be put in place.
On the one hand, the paper concluded that there are, at least in New York, many urban areas that have large numbers of buildings that could be used for NAS. And many of the owners and managers of these buildings were willing to work with officials in a potential emergency. On the other hand, the study identified some issues that needed to be addressed first. First, some of the building managers were a bit concerned about their potential legal liability, and they wanted reassurance that their HVAC would only be used for NAS in emergencies. Second, buildings with multiple tenants could pose a problem. Some tenants might not agree to the use of their HVAC. Building managers had restricted physical access to such areas. However, this problem is not insurmountable, as there are many other HVACs that could be used in their stead.
Prevailing winds, air pressures, and other environmental factors could spread biological agents over a wide area. Therefore, wide-reaching biosurveillance is an important tool when responding to the effects of a release. Governments would need to consider using all available resources to achieve this range. Mobilizing both the public and the private sector could fulfil this need. HVAC systems represent a strong opportunity to use private sector resources to deal with a problem more effectively than BioWatch. Commercial HVAC are more widely dispersed and capture larger air samples than the EPA’s air monitors. And, based on the pilot programme conducted in New York, building managers are willing to work with officials. Repurposing existing commercial HVAC does not rely on new technology to detect biothreats. Moreover, it encourages individuals from the private sector who might not otherwise be involved in the detection process to help out, making biosurveillance a joint private-public sector effort.
HVAC: a small part in the BWC implementation puzzle?
While it may sound far fetched, NAS through HVAC could fulfil a country’s obligations under the 1972 Biological Weapons Convention. According to Article IV, states must take any necessary measures to prohibit and prevent the development, production, stockpiling, acquisition or retention of biological weapons. While this is vague, the Additional Understandings and Agreements reached on this article by the sixth Review Conference, held in 2006, called on States Parties to increase the effectiveness of their surveillance and detection methods at the national level. The fourth Review Conference, held in 1996, had also recognized the need to exclude the use of bioweapons in terrorist or criminal activity. Using commercial HVAC could help State Parties achieve both of these measures, with little new investment.


Last changed: Sep 01 2011 at 8:46 PM




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