Portable gas detectors are small devices clipped to a worker's clothing that warn of toxic gas around the worker. The better systems also include a cloud service that keeps track of every unit and every alarm.
Each detector has sensors that each react to one gas, such as hydrogen sulphide, carbon monoxide or a flammable gas. Hydrogen sulphide is the gas that smells of rotten eggs. It is dangerous because, at high levels, it dulls the sense of smell within minutes. So a worker cannot rely on the nose. The detector shows the reading and sounds an alarm when it passes a limit.
Imagine a worker who enters a storage tank at a chemical plant for cleaning. Before the shift, the detector is tested by exposing it to a known gas. This is called a bump test. In the tank, the low alarm is set at 10 parts per million of hydrogen sulphide and the high alarm at 15. When the reading reaches 10, the detector vibrates, flashes and sounds. The reading climbs to 12 as the worker leaves the tank.
Detectors are of two common kinds. A single-gas detector watches one gas, and it is cheap. A multi-gas detector watches four gases at once, usually hydrogen sulphide, carbon monoxide, oxygen and flammable gas. It also has a motion alarm that sounds if the worker stops moving for a set time, such as 20 or 30 seconds, which may mean that the worker has collapsed. Flammable gas is shown as a percentage of the lowest concentration at which the gas can explode. Workers carry a detector before entering any confined space, such as a tank, a sewer or a pit, where gas can collect and the air can lack oxygen.
The detector also sends the alarm to the cloud when it reaches a network, through the plant's wireless link. The safety team can then see which unit sounded, where and when. The same service reminds the team when a unit is due for a test. The data goes into EHS software, which records the plant's safety incidents.
A fixed system gives a plant-wide warning through fire alarm systems. The portable detector protects the one person who is in the danger. Its sensor is a kind of industrial sensor, and the cloud service is a small example of industrial IoT.