Belmont, Cal., Code of Ordinances ch. 20.5 § 20.5-3

(a) Smoking is prohibited in the following indoor and outdoor places within the City of Belmont, except in places listed in subsection (b) below:
(1) Public places;
(2) Places of employment; and
(3) Multi-unit residence common areas; except that a landlord or common interest development may designate a portion of the outdoor area a smoking area. A designated smoking area:
(A) must be located at least twenty (20) feet from any operable window or door used by the public of an indoor area of a multi-unit residence where smoking is prohibited;
(B) must not include, and must be at least twenty (20) feet from, outdoor areas primarily used by children including, but not limited to, areas improved or designated for play or swimming;
(C) must be no more than twenty-five (25) percent of the total outdoor area of the premises for which it is designated;
(D) must have a clearly marked perimeter;
(E) must be identified by conspicuous signs; and
(F) must not overlap with any area in which smoking is otherwise prohibited by this chapter or other provisions of this Code, state law, or federal law.
(4) Individual units of multi-unit residences, if such units share at least one common floor or ceiling with another such unit.
(5) Service areas;
(b) Unless otherwise prohibited by law, smoking is not restricted by this chapter in the following places:
(1) By performers during theatrical productions, if smoking is an integral part of the story in the theatrical production;
(2) Detached single-family homes and the lots they are sited on, except those used as a child care or health care facility subject to licensing requirements;
(3) Up to ten (10) percent of hotel and motel guest rooms, if the hotel or motel permanently designates particular guest rooms as nonsmoking rooms such that ninety (90) percent or more of its guest rooms are nonsmoking and ashtrays and matches are permanently removed from such nonsmoking rooms. Permanent "no smoking" signage shall be posted in nonsmoking rooms;
(4) Significant tobacco retailers, if at all times minors are prohibited from entering the store;
(5) Individual units of multi-unit residences which do not share any common floors or ceilings with any other such unit;
(6) Any city-designated outdoor smoking areas;
(7) Automobiles;
(8) On streets and sidewalks, unless being used as outdoor workplaces or at city-sponsored events such as parades and fairs.
(c) Nothing in this chapter shall be construed to prohibit smoking in any area in which such smoking is already prohibited by state or federal law unless the applicable state or federal law does not preempt additional local regulation.