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Covering the Bases

It's peanuts, Cracker Jack and sensors, as government researchers test their all-in-one chemical defense system at a California ballpark.
By Andrew Price
Forty Ways of Sniffing Trouble
RDCDS features remote sensors that are capable of detecting more than 40 chemicals, including airborne warfare agents. "Things like mustard gas and sarin fall into this category," says Wu. The sensors can also pick up common toxic commercial chemicals.

While RDCDS is highly effective at sniffing out dangerous substances, the system must be fine-tuned to differentiate between scents that are common to a particular environment and odors that may indicate trouble. "The detectors are extremely sensitive," says Wu. "We need to be able to provide early-warning detection and, as such, they're going to pick up very minute quantities of just about everything."

The RDCDS detectors can sniff the air for a variety of hazardous substances.
An early RDCDS prototype consisted of a single box featuring a pair of detectors. The enhanced system tested at the baseball stadium features eight networked boxes with some 64 detectors. Each of the boxes measures approximately 4 by 3 by 2 feet, plus a 10-foot mast that accommodates video cameras.

RDCDS's detectors combine a variety of different technologies and capabilities, and are sourced from an array of vendors. The approach is designed to counter any attempts by terrorists or other troublemakers to tamper with or otherwise defeat the system. "Rather than just picking the best, we actually picked detectors that detect the same chemicals in different ways," says Replogle.

Redundancy is built into RDCDS's wireless network. "There are three different communications modes."—Ben Wu
Most of the detectors analyze chemicals on the molecular level. One sensor, for instance, might examine a molecule's size while another simultaneously examines its polarity. "They're primarily commercial detectors," he says. "We may have done a thing or two to them, but it's a number of commercial detectors selected through a careful survey of the available technology."

This redundancy also allows more accurate detection. "The idea is that you're detecting the same chemical in two completely different ways," says Replogle. An alarm generated by a single detector immediately attracts attention. "But when both go off," he says, "your confidence level that there's really something to be concerned about goes much higher."
Redundancy is also built into RDCDS's wireless network. "There are three different communications modes; it's a system that was developed here at Sandia," says Wu. "If one channel were to be jammed, the system would automatically switch to the second or even the third mode."

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