Once a year a select group of scientists and engineers gathers at Dugway Proving Ground, a salt flat in the Utah desert 65 km from the nearest traffic light. They are there by invitation of the U.S. Defense Department's Joint Program Office for Biological Defense to compete in an unusual showdown: to field-test their systems for detecting biological warfare agents.

This is no idle contest; this is serious business, critical to national security. As the recent contentious negotiations over the 29-year-old Biological and Toxins Weapons Convention have shown, concern over the possibility of a biological attack is mounting worldwide.

Shortly before the trial gets under way, the competitors make final adjustments to their devices and then retire to trailers nearly a kilometer away. Moments later, an aerosol cloud containing spores of Bacillus globigii is released into the air about 90 meters from the devices. This harmless bacterium simulates a real bioagent such as Bacillus anthracis, the germ that causes anthrax.

As the aerosol cloud passes, the devices collect and prepare air samples, and then feed them through diagnostic tests, looking for the bioagents by using highly specific molecular interactions [see photo]. High-tech versions of the proverbial coalminer's canary, these devices are designed to determine the type and concentration of the agent within minutes, enough time to let soldiers on the battlefield don protective gear. Data are sent to a remote sensing post by wireless modem.

Douglas C. Pizac/AP

A model aircraft plays the role of delivering a biological or chemical weapon [reddye on ground] at Dugway Proving Ground in Utah's Great Salt Lake Desert [above]. After a surrogate bioagent is released, various detectors try to identify it within a matter of minutes.

At the trial's conclusion, the biodetectors are rated on how well and how quickly they identified the surrogate agent, as well as on their ruggedness, power consumption, weight, size, reliability, and safety.

The ultimate goal of the Dugway trials, and of more controlled experiments in the laboratory, is to develop portable, fully automatic, remote sensing systems that can detect a variety of known and novel biological agents before troops on the battlefield are exposed. The dream solution, though still many years off, is a wristwatch-sized biodetector capable of rapid detection, rapid diagnostics, and, potentially, rapid treatment.