Portable gas detector. This device is used to detect gas leaks in an industrial setting. Such detectors are used to check for gases and volatile organic compounds (VOCs), as well as the potentially fatal gas carbon monoxide (CO). Such equipment is also used when investigating and monitoring environmental incidents, such as industrial leaks, hazardous material spills, and emergency responses. This is a MultiRAE infrared (IR) gas photoionization detector (PID). Photographed as part of work carried out by the UK's Health and Safety Laboratory (HSL).