This type of carbon monoxide sensor, although effective in detecting elevated CO levels, will not be waking you up in the middle of the night.
Remember... Carbon monoxide is known as the silent killer. In its latter stages many succumb to confusion and cannot even make a decision to call for help. Thus an early warning device is extremely important.
Also the the recommended life of this carbon monoxide detector is less than 90 days.
If you own one of these CO detection devices the colored dot will become darker when carbon monoxide levels rise. When the CO detector is exposed to fresh air the dot will return to the original color and can be reset in the building.
UL Listed CO alarms are required to have manually operated alarm reset/silence button that will allow you to silence the alarm signal. So for just a few dollars more, why not get a UL Listed unit with an alarm that will alert the whole family in the middle of the night!