NASA will test an electronic nose to sniff for dangerous chemicals in the air on the International Space Station.

The "ENose" is designed to detect ammonia, mercury, methanol, formaldehyde, and other harmful chemicals aboard the space station. The station already contains alarms and other instruments to monitor the air quality, but they don't run continuously as the electronic, shoebox-sized ENose will.

The instrument uses 32 sensors to identify and measure organic and inorganic chemicals, including organic solvents and chemicals that signal the start of electrical fires. NASA explained that the sensors are polymer films that change their electrical conductivity in response to different chemicals. The sensors can detect quantities as small as 10,000 parts per million.

The third-generation ENose weighs less than 9 pounds and runs on 20 watts of power. It can send data to a computer at the ENose lab at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

The original ENose, tested aboard the STS-95 shuttle mission in 1998, could detect 10 compounds, but it could not analyze data immediately. The second-generation device could detect 21 chemicals. The latest version can be trained to identify 40 chemicals. It can quantify them within 40 minutes of detection.

"The ENose is a 'first responder' that will alert crew members of possible contaminants in the air and also analyze and quantify targeted changes in the cabin environment," Margaret A. Ryan, the principal investigator of the ENose project, said in a statement. Space station crew members begin the ENose tests on Dec. 9. If their experiments are successful, the ENose could become part of the space station's monitoring systems. It also could be used for environmental control and life-support system designs for a lunar outpost, said Carl Walz, an astronaut and director of NASA's Advanced Capabilities Division.

"This ENose is a very capable instrument that will increase crew awareness of the state of their air quality," Walz said in a statement. "Having experienced an air-quality issue during my Expedition 4 mission on the space station, I wish I had the information that this ENose will provide future crews."