How China's Pollution Sniffers Work

by Josh Clark
Artificial Olfaction

We saw earlier that China's human sniffers have an advantage over sensitive electronic instrument: as humans, we have physical reactions that corroborate the existence of pollutants. But using electronic instruments eliminates the need to expose humans to harmful pollutants. To this end, science is seeking new ways of using technology to find pollution and determine its concentration.

The ENose detects harmful chemicals in the atmosphere.
Courtesy of NASA/JPL-Caltech

NASA has developed its third-generation Electronic Nose (ENose) device. The space agency's Jet Propulsion Lab (JPL) created the device to help detect ammonia leaks aboard the space shuttle. NASA uses ammonia as a heat conductor in the plumbing of the shuttles. Ammonia can be fatal if one is exposed to it in a gaseous state, and if it leaks, it would mean doom for the astronauts. To fend off a disaster like this, the ENose is being developed for use in space to detect leaks like this early on, before the gas's concentration reaches a deadly level.

The ENose is based on the structure of the human olfactory system. The device uses polymer films to detect and react to molecules, much like the tiny, hair-like receptors on the ends of our olfactory nerves. These reactions are then interpreted by the machine.

An article on the ENose featured on NASA's Web site reports that the device is so sensitive that it can smell an electrical fire before it breaks out and can differentiate between Coca-Cola and Pepsi [Source:NASA]. Even the Chinese sniffers would have trouble doing that.

Robotic dogs are finding new purpose as pollutant detectors.
Courtesy of Natalie Jeremijenko,
Jeffrey Warren and Mike Kai ­
Robotic dogs are finding new purpose
as pollutant detectors. The dogs’
microchips are being retrofitted to
sense volatile compounds in the air.

Back on Earth, slightly less sophisticated technology than the space shuttle is being used for a device similar to NASA's ENose. Robotic dogs, the once-popular kids' toys that can walk, sit, stay and bark, are being retrofitted with new chips that allow the canines to sense volatile compounds in traces as little as 100 parts per million in a project called the Feral Dog Project.

The brainchild of Natalie Jeremijenko, a San Diego State University professor, the project began as a way not only to sniff out pollutants safely, but also to raise awareness of the environmental hazards that these pollutants pose. The project has taken off, with retrofitting labs cropping up around the country in Idaho, New York and Florida.

But the sensors used in the Feral Dog Project have a long way to go before they catch up to the ENose. While the robotic dogs' sensors can pick up compounds in 100 parts per million, ENose sensors are capable of detecting as little as one part -- that's just one molecule -- per million.

For more information on the Feral Dogs Project and a video featuring a robot dog release, check out the links on the following page.