Neb. Rev. Stat. § 81-5,145

Sections 81-5,132 to 81-5,146 shall prohibit a political subdivision from adopting standards less stringent than those provided in sections 81-5,132 to 81-5,146 and rules and regulations adopted under sections 81-5,132 to 81-5,146 , except that, as to buildings constructed on or after January 1, 1982, such political subdivision shall require that smoke detectors be attached to a centralized electrical power source within the building which may be equipped with a battery as an alternate power source. No political subdivision shall require that a smoke detector be attached to a centralized power source within a building constructed prior to January 1, 1982.