DETECTION THE AIR T
he building’s ventilation system will circulate the deadly air from the release fl oor to the rest of the building in minutes before anyone
knows that anything is happening. Building occupants are basically trapped inside the building envelope. Imagine the news footage on television and across the web. What impact would such an event have on commercial real estate as a whole? Would you go to work in your offi ce building aſt er such a catastrophe? This scenario is not so farfetched. It
has been highlighted by all main US and UK government departments. We have been lucky to date. However, experts defer that this type of event is no longer an “if”, but is now a “when”.
Early protection Immediately following 9/11 a myriad approaches were introduced to protect the air within critical buildings. The National Institute for Occupational Safety and Health (NIOSH), Federal Emergency Management Agency (FEMA), US Army Corps of Engineers and Lawrence Livermore National Laboratory all recommended passive solutions, including covering, disguising or relocating vulnerable fresh air intakes on or near ground level. Unfortunately, these passive responses provide no protection to an internal release or an external plume scenario, and are also cost-prohibitive from a construction perspective. The agencies went for fi ne high-
effi ciency HEPA (High-Effi ciency Particulate Air)-level particulate air
THAT I BREATHE
Mike Welden presents the latest developments in CBRN sensors inside buildings
As a CBRN professional, you know the vulnerability of buildings to an airborne toxic release. Think about it. All a terrorist or disgruntled employee would need to do is to buy or steal some chlorine gas from a pool supply house, cyanide from a jewellery supplier, arsine from a manufacturing plant or grab another toxic industrial chemical – all easily accessible – and discharge the toxic chemical either into a fresh-air intake or go to any fl oor inside the building and release the toxic gas.
amount of time required to react and proactively save lives.
Central business district plume release scenario. Building HVAC systems will ingest the toxic air and circulate it throughout the building potentially poisoning hundreds of innocent people. Image property of BPSI, used with permission
fi ltration that can be put in place to capture organic particles or particles from a radiological dispersal device. However, these fi lter systems do little to protect against a toxic chemical gas. Ultraviolet lighting installed in ductwork and electrostatic fi ltering was also recommended, but these passive alternatives have extreme limitations and oſt en prove too costly to maintain. Enter the age of access control,
cameras and the EPO (emergency power off ) switch. These systems improve security, but can provide an illusion of safety. Cameras can provide forensic evidence. EPO switches, push button HVAC (heating, ventilation, air condition- ing) shutdown, but are dependent on the decision-making speed, location and capability of a user who may in fact be exposed and unable to act. All these solutions provide traditional protections, but prove limited under the scenario of an airborne toxic release due to the short
First-generation dumb sensors Given the shortcomings of passive and traditional building protection to an airborne release, technologists took IMS (Ion Mobility Spectrometry), SAW (Surface Acoustic Wave), and other detection technologies such as GC (Gas Chromatography) and worked to ruggedize such laboratory-based core technologies for placement into critical commercial or government buildings. The concept of continuously monitoring the air for toxics was born. These early sensors might light up
upon detection or send a go/no go signal to a security control room. While they were the best available at the time, their limitations were extraordinary. They proved unreliable with a high false- positive rate and were unable to operate in everyday commercial environments – with multiple interferents such as cigarette smoke, diesel exhaust or cleaning solutions. Additionally, with the various consumables needed to keep the detectors operating coupled with regular calibration and other preventative maintenance, the sensors proved to be very expensive to own and run. As a result, few users of this early fi rst- generation technology integrated them into their Building Automation Systems (BAS) due to the lack of reliability.
Next-generation autonomous system In 2008, sensor systems took a leap forward. The approach of placing reliable
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