It is difficult to judge a device that is silent: when everything goes well he said nothing! but it is an essential safety as smoke sensors that we already have. We put at the door of our room and he analyzed pe, da, t all winter air emanating from our POELLE wood. No warning, but we slept with the spirit avos safe! If we judge by the battery life on smoke sensors, we will not replace them before a year on this carbon monoxide sensor.
