Electronic Nose. At 3mm square, several chemical sensors could fit inside a filter. (Images courtesy of Carnegie Mellon)

In research with narrow purpose but broad potential, scientists from Carnegie Mellon University have teamed with the National Institute of Occupational Safety and Health to develop a chemical sensor to fit inside respirator filters that tells users when filters need replacing.

Today, filter life is estimated, based on federal work-safety models. But when wearers are exposed to a stew of unknown hazards in emergency situations, disquieting guesswork comes into play. That’s what drove scientists at NIOSH’s National Personal Protective Technology Laboratory in South Park, Pa., to commission the university in Pittsburgh to help devise a solution.

The specifications are daunting. The sensors must not interfere with filter function. Their readings must be wirelessly communicated. They also have to test for an array of toxins and know when accumulated exposure to any one of them is too much. And it has to work very fast.

Now, researchers from the disciplines of chemistry, electronics, micromechanical engineering and nanotechnology think they have cracked the case. They have developed a class of polymers that can give discrete electrical responses to an array of chemicals within seconds of exposure. They have a technique for applying polymer dots about 1Ú10 the size of a period on this page to a bed of electrodes, and then suspending that on a vibrating pad, whose changes in frequency will help calculate accumulating exposure and then transmit the data outside.

Three years into the $1-million-a-year project, Gary Fedder, co-director of the university’s Microelectromechanical Systems Laboratory, says they are about half way to a commercial device for respirators. He sees broader security potential, however, and says the project could be accelerated. m "It’s not lost on us," he says.