Carbon monoxide detectors can be cheap insurance against the "silent killer".

To meet UL Standard 2034, detectors must sound an alarm. For higher concentrations the alarm sounds in less time, while lower concentrations can take longer to trigger the alarm.

Models currently on the market are powered either by 110 volt house current or batteries. Batteries have one problem: occupants may allow them to run down. Units powered by house current don't need new batteries. However, 110v models will not operate if power to the building is lost.

Until someone markets a detector that's hard wired with battery backup, you'll have to choose which power source makes you feel safer. Or, you could install two: a hard wired model near the combustion device and a battery-powered model near the bedrooms.

Search the Oikos Product Directory for a list of CO detector suppliers.