Smokers must be greater than 20 feet from a public building's entrances or operable windows while in the act of smoking. This is governed by California Government Code, 7597.

7597. (a) No public employee or member of the public shall smoke any tobacco product including e-cigarettes or vape pen inside a public building, or in an outdoor area within 20 feet of a main exit, entrance, or operable window of a public building, or in a passenger vehicle, as defined by Section 465 of the Vehicle Code, owned by the state.