2009 Virginia Uniform Statewide Building Code (USBC; see pages 37 and 80):
The 2009 Virginia Uniform Statewide Building Code (USBC) requires the installation of CO alarms in new detached one- and two-family dwellings, townhouses, and Group-R occupancies (e.g., hotels, dormitories, apartment buildings). (Effective date = March 1, 2011)