These single-gas, multi-gas, PID monitors, controllers, and wireless alarm bar can be installed to provide continuous, always-on monitoring for toxic gases and gamma radiation. Mostly toxic gases are monitored and measured in parts per million (ppm) range while Oxygen is measured in percent volume. Combustible gases are generally measured as 0-100% of the lower explosive limit (LEL). Portable gas detectors are classed as a type of Personal Protective Equipment (PPE), designed to keep personnel safe from gas hazards and allow mobile testing of locations before they are entered. These small devices are essential in many areas where gas hazards could occur, because they are the only means of monitoring an operator’s breathing zone continuously, whilst stationary and moving.