A new requirement for carbon monoxide detectors in Washington homes takes effect on Jan. 1.

State law has required the alarms in new construction beginning in 2011. But the 2013 law requires the detectors in all existing residences, including apartments, condos, hotels, dormitories and residential institutions.

Owners of single-family homes will be required to have the detectors when their home is sold or when they apply for a remodeling permit.

The carbon monoxide alarms look similar to smoke alarms. They can be hard-wired or battery powered. They are sold where smoke alarms are sold, and some models are combined with a smoke alarm.

Prices range from $25 to $40.

Follow installation directions, but generally alarms should be located outside bedrooms, with one alarm on each level of a home.

To learn more, visit the State Department of Enterprises Services website at fortress.wa.gov.