Idaho Administrative Code IDAPA 07.03.01(2012 IRC Adoption)::
Detached one- and two-family homes and townhomes (dwellings) of not more than three stories within which fuel-fired appliances are installed or which have an attached garage must install CO alarms in the general vicinity of each sleeping area. (Effective date: January 1, 2011)

Note: Although the Idaho Division of Building Safety has adopted the 2009 International Residential Code (IRC) requirements, each city or county is individually responsible for adopting and enforcing the building codes.