A U.S. Army ranger is on a battlefield in a country known to be making chemical weapons. Through his binoculars, he spots a cloud of smoke a mile away. Does it contain lethal gas? At the moment, there is no easy way to know. But researchers at Sandia National Laboratories and MIT are working on a dime-sized sensor that could be built into binoculars or telescopes to spot toxic gases before they do any damage.

The sensor identifies the infrared absorption spectrum of a gas. When a toxic gas is picked out, the system alerts the user. The researchers, who include MIT’s Steve Senturia and Sandia’s Mike Butler and Mike Sinclair, expect to test an experimental device this fall; they hope to build a lab prototype within two years. Although the device is being developed for the military, it carries obvious peacetime uses-fighting chemical fires being one.