A new sensor aboard the International Space Station will check continuously for harmful chemicals in air breathed by station crew members, NASA announced. That sensor also can serve as a fire and smoke alarm.

Astronauts on the current Space Shuttle Endeavour STS-126 Mission will unpack the experimental sensor, called the ENose, Dec. 9.

Serving aboard spaceships and the space station necessarily poses risks to astronauts, and one danger is that hazardous chemicals aboard spacecraft can leak into the air in the confined space of the station or space shuttle orbiter.

ENose will check space station air for such dangerous substances as ammonia, mercury, methanol and formaldehyde.

That last substance may be used in many home building products such as plywood, particleboard floor joists, composition materials used in cabinets, and the like. Formaldehyde, which can off-gas from such materials, can cause lung problems up to and including cancer. But at least when such materials are used in home construction, outside air filters into a home, so its air changes every few hours.

Not so in space.

The ENose fills the long-standing gap between onboard alarms and complex analytical instruments. Once installed, the ENose, will run continuously and autonomously. It is the first instrument on the station that will detect and quantify chemical leaks or spills as they happen.

"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," said Margaret A. Ryan, principal investigator of the ENose project at the Jet Propulsion Laboratory, or JPL, in Pasadena, Calif. JPL built and manages the device.

Station crew members will unpack the ENose Dec. 9 to begin its six-month demonstration in the crew cabin. If the experiment is successful, the ENose might be used in future space missions as part of an automated system to monitor and control astronauts’ in-space environments.

"This ENose is a very capable instrument that will increase crew awareness of the state of their air quality," said Carl Walz, an astronaut and director of the NASA Advanced Capabilities Division, part of the Exploration System Mission Directorate, which funds ENose.

"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. This technology demonstration will provide important information for environmental control and life-support system designers for the future lunar outpost."

The shoebox-sized ENose contains an array of 32 sensors that can identify and quantify several organic and inorganic chemicals, including organic solvents and marker chemicals that signal the start of electrical fires.

Here’s how it works: The ENose sensors are polymer films that change their electrical conductivity in response to different chemicals. The pattern of the sensor array’s response depends on the particular chemical types present in the air.

It can analyze volatile aerosols and vapors, help monitor cleanup of chemical spills or leaks, and enable more intensive chemical analysis by collecting raw data and streaming it to a computer at the JPL ENose laboratory. The instrument has a wide range of chemical sensitivity, from fractional parts per million to 10,000 parts per million. For all of its capabilities, the ENose weighs less than nine pounds and requires only 20 watts of power.

The ENose is now in its third generation. The first ENose was tested during a six-day demonstration on the STS-95 shuttle mission in 1998.

That prototype could detect 10 compounds, but could not analyze data immediately. The second-generation ENose could detect, identify and quantify 21 different chemicals. It was extensively ground-tested.

This third-generation ENose includes data-analysis software to identify and quantify the release of chemicals within 40 minutes of detection. While it will look for 10 chemical types in this six-month experiment, the new ENose can be trained to detect many others.

Aside from airborne chemicals in the close confines of the station or a shuttle orbiter vehicle, astronauts also face myriad other dangers, some of which are unavoidable.

For example, space radiation bombards any craft in space, and the occupants of that craft. Occasionally an astronaut will see what he or she perceives as a flash of light, when in fact there is no flash. Rather, a bit of radiation has pierced the hull of the craft, entered the astronaut’s eye and struck the retina.

On months-long missions in space, the lack of gravity causes astronauts’ bones and muscle mass to atrophy. Perhaps 10 percent of an astronaut’s bone mass may disappear on an expedition to the space station.

Other problems may arise, such as persistent nausea in the absence of gravity.

And yet, knowing all this, astronauts vie for the chance to go to space.