Beginning January 1, 2014, these alarms are now required in all homes and condos when they are purchased. Carbon Monoxide alarms have been required in all new homes since 2011 in the State of Washington.
Placement of these alarms is key to preventing health issues. They are to be placed outside each separate sleeping area on each level of a residence. Be sure to change the batteries annually, even if your alarm is wired to the electrical supply, it will need those back up batteries in case of a power outage.
Like smoke detectors, this is an easy but very important safety issue. Carbon monoxide is an odorless, invisible gas that can cause death when breathed in a matter of minutes.
For this reason, Keith Schenk with Certified Home & Commercial Inspections always checks for carbon monoxide alarms as well as smoke detectors and includes this information in his inspection reports.
This diagram illustrates proper placement of carbon monoxide alarms in a home as well as sources of Carbon Monoxide commonly found in homes.