Intermittent, low level warning at 55 parts-per-million and continuous warning if it reaches 100 PPM. Piercing, 85 dB alarm is sure to wake you up! For optimum safety, install one on every floor of your home. (CO poisoning can lull its victims into a deep sleep.) Advanced semi conductor sensing technology with self-diagnosing circuitry prevents false alarms. No batteries or expensive sensor to replace and nothing to install - just plug it in. Special rotating plug lets you plug it in vertically or horizontally. Power-on, warning indicator lights, five year warranty, UL listed, 115V, Canadian made.