Recognizing that the current generation of bio-aerosol detectors still gives off too many false alarms, which in turn can have a costly series of consequences, scientists at Sandia National Laboratories are developing technology that could be integrated with existing bio-sensing systems to provide a second look at air samples before an alarm is sounded.
“The way the Enhanced Bioaerosol Detection System (EBADS) program started was that the Department of Homeland Security and others at the lab said there are a lot of these laser induced fluorescence (LIF) sensors like Air Sentinel and Bioalert and other fluorescence ones that are pretty close in terms of their false alarm rate but they’re not there yet,” Tom Kulp, the principal investigator on the project at Sandia, tells TR2.
When a facility has to be closed down due to false alarms or what turns out to be a harmless security breach, which often means higher costs.
“When we looked at sensors we found that the impacts [from false alarms] could be pretty significant for the ones we looked at we looked at,” Kulp says.
Basically Sandia and its partners, including Lawrence Livermore, Oak Ridge and Pacific Northwest National Labs, are developing a capability that could be incorporated into existing sensor systems to help reduce the false alarm problem.
“It would be beneficial for industry in the sense that we’re keeping an eye on what industry can do and it would be best to solve the problem with something that’s available to them rather than them having to tool up and make up a whole bunch of exotic new widgets that they don’t normally make,” Kulp says.
As part of the research for EBADS, Sandia found through testing of air flows that are being collected by some existing sensors is that they have trouble distinguishing biological from non-biological particles. A common example is diesel soot, Kulp says. Certain sensors will fluoresce in a way that says this is a problem, and then will alarm.
Under EBADS Sandia has developed a method to look at the sample that has already been examined by the primary early warning sensor and is ready to provide a general alarm. This “adjunct” or “parallel” channel developed by Sandia would confirm if an alarm should be sounded, Kulp says. EBADS, like the early warning sensors it hopes to enhance, isn’t meant to identify a threat, just warn that there is a potential problem.
The second look channel developed by Sandia involves staining particles that become fluorescent in the presence of proteins and then running them through a flow cytometer to examine for an unusual amount of protein, Kulp says.
“And if we see an unusual amount of protein containing particles, we believe that would be a better indicator or a parallel indicator with some of these existing sensors,” he says.
The cytometers are already common technology that are becoming less and less expensive and could be adapted to existing bio-aerosol sensor systems, Kulp says. During the development of EBADS Sandia has strived to keep costs in mind for any product the backup sensor system could be adapted to, he says.
So in the first phase of the program Sandia was able to demonstrate what was causing false alarms with existing sensors. In a second phase Sandia and researchers from Oak Ridge National Laboratory used the newly developed EBADS method and tested blind samples provided by the Army’s Edgewood Chemical Biological Center, correctly determining with each whether there was cause for an alarm.
In February 2008 the program will move to a new phase involving DHS-specified real-world tests in an office building, a major U.S. subway station and airport. Those tests will last a combined three months. For the tests aerosol to liquid collectors will be deployed alongside existing sensor systems and take in samples with each alarm. The samples will be sent back to Sandia and run through EBADS to confirm if an alarm was valid.
If the next test phase is successful, Sandia hopes to begin working with industrial partners next summer who can tie their manufacturing and engineering skills to adapt EBADS to an existing sensor system, Kulp says.
In addition to the work Sandia and its partners are doing to reduce the false alarm rates in early warning bio-aerosol detectors, DHS is also funding similar projects among the partners. Lawrence Livermore is working on a charge detection-based technology under EBADS. The team is also investigating a third methodology that hopes to look at using multiple laser excitations of samples to reduce false alarm rates.