A sensor unit comprising a heat resistant shell, the shell having a plurality of viewing windows spaced around the shell exterior to define a 360° view around the unit, each viewing window being optically coupled to an infrared pyroelectric sensor and an infrared thermopile sensor, the interior of the shell defining a chamber containing at least two different smoke detectors, the shell having ventilation holes communicating with the chamber and temperature sensors mounted on the unit, the shell housing at least one printed circuit board coupled to the sensors and detectors and supporting a computer and radio transmitter, and a rechargeable power source powering the printed circuit board.