Government Code § 66337

(a) For purposes of any fire or life protection ordinance or regulation, a junior accessory dwelling unit shall not be considered a separate or new dwelling unit.

(b) This article shall not be construed to prohibit a city, county, city and county, or other local public entity from adopting an ordinance or regulation relating to fire and life protection requirements within a single-family residence that contains a junior accessory dwelling unit so long as the ordinance or regulation applies uniformly to all single-family residences within the zone regardless of whether the single-family residence includes a junior accessory dwelling unit or not.