Washington State Uniform Building Code requires smoke detectors in each residential sleeping room. The code also requires one detector in the basement, in a hallway leading to bedrooms and on each floor of a multistory home. As of 2013 the State Building Code Council also requires that CO alarms be installed in non-owner occupied properties outside of each sleeping area in the immediate vicinity of the bedroom and on each level of the residence.
Chapter 51-51 WAC – 51-51-0314 – WASHINGTON STATE BUILDING CODE
Section R314 – Smoke alarms. Location.
Smoke alarms shall be installed in the following locations:
1. In each sleeping room.
2. Outside each separate sleeping area in the immediate vicinity of the bedrooms.
3. On each additional story of the dwelling, including basements and habitable attics but not including crawl spaces and uninhabitable attics. In dwellings or dwelling units with split levels and without an intervening door between the adjacent levels, a smoke alarm installed on the upper level shall suffice for the adjacent lower level provided that the lower level is less than one full story below the upper level.
4. In napping areas in a family home child care.