Electronic 'rescue dog' can sniff out people trapped in debris

Scientists have developed a measuring device with small and extremely sensitive gas sensors that can find people trapped under debris, just like trained rescue dogs.

The sensors developed by researchers at ETH Zurich in Switzerland can detect acetone, ammonia, and isoprene - all metabolic products that we emit in low concentrations via our breath or skin.

These were combined with two commercial sensors for CO2 and moisture, to create a device useful when searching for entrapped people.

To test the device, researchers used a test chamber at the University of Innsbruck in the UK as an entrapment simulator. Volunteers each remained in this chamber for two hours.

"The combination of sensors for various chemical compounds is important, because the individual substances could come from sources other than humans. CO2, for example, could come from either a buried person or a fire source," said Andreas Guntner, lead author of the study published in the journal Analytical Chemistry.

The combination of sensors provides the scientists with reliable indicators of the presence of people.

Researchers also showed that there are differences between the compounds emitted via our breath and skin.

"Acetone and isoprene are typical substances that we mostly breathe out. Ammonia, however, is usually emitted through the skin," said Sotiris Pratsinis, professor at ETH Zurich who led the study.

In the experiments in the entrapment simulator, the participants wore a breathing mask. In the first part of the experiment, the exhaled air was channelled directly out of the chamber; in the second part, it remained inside. This allowed the scientists to create separate breath and skin emission profiles.

The gas sensors are the size of a small computer chip.

"Our easy-to-handle sensor combination is by far the smallest and cheapest device that is sufficiently sensitive to detect entrapped people. In a next step, we would like to test it during real conditions, to see whether it is suited for use in searches after earthquakes or avalanches," he said.

While electronic devices are already in use during searches after earthquakes, these work with microphones and cameras. These only help to locate entrapped people who are capable of making themselves heard or are visible beneath ruins.

The ETH scientists' idea is to complement these resources with the chemical sensors. They are currently looking for industry partners or investors to support the construction of a prototype.

Drones and robots could also be equipped with the gas sensors, allowing difficult-to-reach or inaccessible areas to also be searched. Further potential applications could include detecting stowaways and exposing human trafficking.