LED Bargraph changes color as ozone levels increase: green indicates a safe level, yellow is CAUTION level, and red is the DANGER level. Features a heated metal oxide semiconductor (hmos) sensor for excellent sensitivity and quick response time. Also features an audio alarm and relay output that are triggered at 0.1 ppm (DANGER level) and a 0 to 3 VAC recorder output. Order optional Calibrator to verify that your ozone Detectors are conforming to their original calibration. Fixed system alerts workers to hazardous ozone levels easy-to-read, multicolor graphical display. Hmos sensor for superior sensitivity.