The system is designed as a safety feature for the hydrogen-gas filling stations of the near future, which are expected to spring up as fuel-cell cars come into wider use.

The system uses tiny hydrogen sensors connected to wireless transmitters.

Each sensor-transmitter combination is called a node, and signals are radioed from each node to a server at a base station.

The sensors can detect hydrogen gas in amounts of as little as 100 parts per million. When a gas leak is detected, the communications circuitry gets activated and the transmitter sends a signal to the base station with information regading the extent of the leak. The server monitors the data and responds by sending commands back to the location of the node to turn on a fan to disperse the gas and to close the pipe valve.

The prototype sensor measures 7.5 x 3mm and the entire node including battery and transmission circuitry measures just 5cm square. Each node can run for six to 12 months on its battery.

Hitachi aims to make the nodes even smaller and have a practical version of the technology ready in around 2008 for hydrogen filling stations.