The worry over Andrew Speaker's air travel across the Atlantic in May while infected with a drug-resistant strain of tuberculosis has died down. But it has given researchers added incentive to complete work developing sensors that could be used to immediately detect and locate not only sick airline passengers but those with more nefarious goals such as contaminating the air with hazardous biological or chemical materials.

Researchers with the Air Transportation Center of Excellence for Airline Cabin Environment Research are testing a system that uses mathematical models and sensors designed to pinpoint problem passengers down to their seat number and alert flight and ground crews of an emergency.

The key to successfully tracing the source of an airline cabin threat is inverse computational fluid dynamics modeling, which analyzes how a material disperses throughout the cabin and then runs the dispersion in reverse to find its origin, says Qingyan (pronounced Chin-Yan) Chen, a Purdue University professor of mechanical engineering and principal director of the center, which was formed and is funded by the U.S. Federal Aviation Administration (FAA). Sensors track the airflow pattern and collect data related to factors such as temperature, velocity and concentration of gases and particles in the air.

To test their sensor technology in the most realistic environment possible (without endangering unwitting vacationers or business travelers on actual flights), Chen and his team are working in a mock airline cabin at Purdue's Ray W. Herrick Laboratories. This passenger cabin, realistic down to its rows of uncomfortable seats (although, sadly, sans the stale peanuts or pretzels) is equipped with three sensors and recreates passenger exhalation and body heat as well as an airliner's environmental control system, which supplies fresh and recirculated air. Using this setup, researchers say they've been able to track an airborne substance to within about two feet of its origin in an airline cabin.

At this stage, researchers are developing mathematical models that could be written into the software needed to operate such a tracking system and are learning where to place sensors within a cabin to accurately trace hazardous airborne materials back to their source.

In the case of Speaker—the American lawyer who traveled abroad despite being warned not to because of tuberculosis—if a sensor programmed to identify the TB virus detects its presence "then our model will give you real-time information about when, where, and how much of the TB virus was released into the cabin," Chen says, adding that airlines could even install a special filter to help remove the TB virus from the cabin air supply.

Technology challenges abound in the quest to build a working sensor that has the computational speed required to alert airlines quickly in case of an emergency, but is also cheap enough for financially strapped carriers to use. "Our model is very complicated and needs massive computing power," Chen says. "If you were to use your desktop computer, it would take days to complete these computations." Chen and his team are investigating not only faster CPUs but explosively fast graphics cards that video gamers rely on for more realistic images.

The center's long-term goal is to influence aircraft design to improve air quality. "You need to know where contaminants are in the cabin," says William Gale, a professor at Auburn University and the center's executive director. "If someone starts coughing, who would be affected by the aerosol?"

The Federal Aviation Administration established the center in 2004 under a Congressional directive to study air quality problems in airline cabins in the wake of the previous year's severe acute respiratory syndrome (SARS) outbreak in Asia, which later spread to more than two dozen countries in North America, South America and Europe. So far, Congress has forked over more than $10 million to the effort; Chen estimates that his team's work so far has cost about $500,000. The center works with more than 20 companies, including airplane manufacturer Boeing, Delta Airlines and GE Aviation.

Science and technology aside, perhaps the greatest hurdle to implementing safety measures is the airlines' recent financial struggles. "Since so many airlines are coming out of Chapter 11," Chen says, "we're hoping that Congress will fund it."

Speaking of financial troubles, nine people yesterday filed a $1.3 million lawsuit against the globe-hopping TB patient, charging that he may have exposed them to the disease.