Sensing Danger Within

April 2006
By Maryann Lawlor
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The Sensors for Immune Building (SIB) Program underway at the Defense Advanced Research Projects Agency (DARPA) has been developing point and standoff sensors to detect biological and chemical agents within facilities. It is part of the larger Immune Building Program that also is developing the supporting systems to protect personnel during an attack involving hazardous materials.
Programs develop capabilities to protect personnel in military facilities.

Electronic bloodhounds that quickly and reliably detect dangerous substances in a closed environment will begin replacing current sensors in military facilities in the near future. The final elements of a program borne out of the need to defend warfighters against biological and chemical agents will enter the transition stage later this year. The goal is to expand protection to the rest of the military work force. This added security is part of a two-year effort to develop extremely fast and accurate sensors that are so cost-effective that they can be used on a large scale.

A heightened concern about threats of chemical and biological attacks within buildings is the impetus for the work. Although technologies are available to protect military personnel on the battlefield, many are unsuitable for use inside facilities. Working with industry and a national laboratory, the Defense Advanced Research Projects Agency (DARPA), Arlington, Virginia, tackled this shortcoming by studying how to exploit architectural infrastructures to protect building inhabitants.

The overarching project is called the Immune Building Program, established under the auspices of DARPA’s Special Projects Office. The initiative’s ultimate goal is to make military buildings, such as barracks, offices and command and control centers, less attractive targets for chemical or biological attacks by reducing the effectiveness such strikes would have. To accomplish this, researchers set out to improve the ability to protect personnel, restore operations quickly after an attack and preserve forensic evidence for treatment and retaliation.

However, in their quest to accomplish these tasks, DARPA researchers discovered that the sensors required to alert warfighters about an attack were inadequate because they were neither fast nor accurate enough. As a result, the agency created the Sensors for Immune Building (SIB) Program, which has been examining sensors and the associated systems necessary to detect rapidly and to verify accurately biological and chemical agents.

Dr. Wayne Bryden, program manager, Immune Building and Sensors for Immune Building programs, Special Projects Office, DARPA, explains why speed and precision are two very important requirements for sensor systems used within buildings. “If you’re going to try to be proactive about protecting people, the faster your sensor response, the better your system will work. But you don’t want it to false alarm. You don’t want to be emptying people out of a building every time a sensor goes off because [then] people start ignoring the alarms,” Bryden says.

These requirements distinguish sensors used in buildings from those deployed in the battlespace, he explains. Battlefield sensors are designed to signal an attack so warfighters can respond, and some false alarms can be tolerated. The sensors being designed in the SIB Program are not meant to replace tactical sensors that have the size, weight, power and sufficient performance for their mission. “The mission here is much more challenging. It [the sensor] has to run all the time and never false alarm,” he notes. Bryden adds, however, that some could enter the tactical environment once they have been ruggedized and hardened.

The SIB Program is developing both point and standoff sensors. Point sensors come into physical contact with an agent of interest then sound an alert. A smoke detector is a type of point sensor. Standoff sensors, on the other hand, are devices such as lasers that send out a beam of light that changes when it encounters a dangerous biological or chemical substance. Standoff chemical sensors reduce filtration and operating costs by allowing an on-demand filtration of external threats.

Determining how many sensors must be installed in buildings to ensure adequate protection is another issue the DARPA team has addressed. Bryden explains that while there is always a trade-off between sensor costs and number installed, according to systems studies conducted as part of the Immune Building Program, only a few devices are needed for effective coverage. And a building’s heating, ventilation and air conditioning (HVAC) system is the key. A 30,000- to 40,000-square-foot building, for example, typically has less than five HVAC zones. The number of sensor sets required to monitor a building of this size is only around a dozen, Bryden says.

“We trade off the cost of the sensor with the cost of getting the sample to the sensor. You can use a sensor and share it among many locations by putting a sampling system together that pulls air from different rooms and allows you to sequence that through a sensor rather than putting a sensor in every location. That works pretty well. The studies have shown that this approach is practically as effective as having sensors everywhere, but much cheaper,” he notes.

One advantage the SIB Program enjoys over programs developing tactical sensors is in power requirements. Battlefield sensors must be small, lightweight and power efficient. Because sensing devices installed in buildings can be powered by the existing electrical system, their design is not dictated by power supplies.

But detection through the use of trigger sensors is just part of the protection equation. The program also is developing biological and chemical sensors that quickly confirm the presence of an agent. One of the biological confirmatory sensors, called the Rapid Detection of Virions in Air, uses video imaging to detect binding.

To describe the process, Bryden uses the analogy of a human body being attacked by a flu virus. “If the virus is roughly the same as last year’s strain, the body has already built up antibodies to respond. If you do that same sort of process in an animal first and make antibodies against all sorts of different agents, you can have a lock-and-key mechanism. This antibody binds with that particular agent reasonably specifically. That’s what one version of that fast biological confirming sensor is. If you take that antibody that some animal made and put a label on it such that it lights up while binding, then you could put them under a microscope, and when the binding happens, you can see it by video. It’s a microscopic view of that binding event. That’s how you get it fast—by having this look at it when it’s first created,” he explains. “This technique is very fast and takes advantage of video, cameras and microscopes to get the speed and specificity that we need to protect people.”

Confirming samples has been one of the drivers for the SIB Program, Bryden allows. Existing processes can take 15 minutes to 30 minutes. “We’d like it to be a minute or less—reduce the time element by at least a factor of 10,” he says.

The military services carry out force protection exercises to practice how to respond to a chemical or biological attack. In the U.S. Navy, sailors test a substance that represents anthrax that was thrown aboard a guided missile cruiser.
Sample analysis has been another driving factor for the project. One sensor the DARPA team is working on is the Rapid Autonomous Integrated DNA Detection System, or RAIDDS. The system is basically a multiplex preliminary chain reaction (PCR) machine that looks at the genetic code of an organism and identifies it.

Bryden relates that the gold standard for organism viability tests in all biodetection laboratory analysis is still several hours to overnight for some samples and up to a week for others. “That’s a long time. The faster you know something is going on, the faster you can give people antibiotics or other treatments. So you really want to know if that organism is viable,” he says. To address this issue, the DARPA team has launched a viability assay to determine whether it can hasten that process. The work combines microbiological growth and molecular tools such as PCR. The tests can indicate that a sample is viable much sooner than visual cues.

The final step in safeguarding personnel working inside buildings is the ability to take action once a dangerous agent has been detected. Because a building’s HVAC system is the source of air circulation, it is once again a key component. As part of the Immune Building Program, researchers have been developing the algorithms and demonstrating the ability to shut down an HVAC system automatically and keep the air flow stable to stop an agent from spreading. Simultaneously, the process of assessing the agent begins, so a decision can be made about whether evacuation is necessary or even more drastic steps must be taken. “That’s how this layered approach of sensing, countermeasure, sensing again and another countermeasure works, all built into algorithms for protecting buildings,” Bryden says. The entire process would take place in a matter of minutes or less, he adds.

Work on the Immune Building and SIB programs has been a collaborative effort. Several small and large companies are under contract with DARPA, and researchers at Lawrence Livermore National Laboratory are working on the project. DARPA also is funding the Edgewood Chemical Biological Center, a U.S. Army Research, Development and Engineering Command laboratory at Aberdeen Proving Ground, Maryland.

Some of the systems within the Immune Building Program have developed prototype hardware, several of which are in the process of government testing. From there, the technologies have been or will be transitioned to a variety of partners, including the military and homeland security agencies.

“We’ve been very cognizant in this whole set of programs of making the cost affordable so we can put these systems in. We can make this incredibly expensive, but we’re trying to demonstrate at small scale first and get it out there on a large scale eventually,” Bryden explains.

Several of the sensors from the SIB Program already have entered the transition phase; more are scheduled for transition by the end of fiscal year 2006. But Bryden and DARPA’s leadership recognizes that the conclusion of projects does not mean the end of discovery. “Bring me your great ideas,” Bryden advises. “Go to the DARPA Web site. Each office has an officewide Broad Agency Announcement that talks about our interests around the office and gives specific points of contact. Program managers like myself love talking to people about their ideas. That gets me jazzed.”


Web Resources
Sensors for Immune Building Program:
Immune Building Program:
Edgewood Chemical Biological Center:

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