Cal. Civ. Code § 146

  § 146. Egress from apartments. 1. There shall be at least two means of
egress from every apartment or suite. Such means shall be remote from
each other. Except where it opens into a stair as permitted in
subdivision three, one means shall be to a public hall connecting with a
stair, fire-stair or fire-tower, not more than fifty feet distant from
such means. In dwellings erected under plans filed in the department
after September first, nineteen hundred fifty-one, such stair,
fire-stair or fire-tower shall be enclosed. The other required means of
egress shall open either directly upon a fire-escape or directly on a
fire-tower balcony or a public vestibule or other public hall connecting
with a stair, fire-stair or fire-tower balcony.
  2. Except as hereinafter provided for dwellings two stories or less in
height such balcony, vestibule, hall or stair shall be separated from
the public hall or stair on which the first means of egress opens by a
fireproof wall, unpierced unless by an opening equipped with a fireproof
door and assembly with the door self-closing. Such door shall not be
held open by any device whatever. In a dwelling two stories or less in
height, the separating wall may be fire-retarded on both sides in lieu
of being fireproof.
  3. In a dwelling three stories or less in height and occupied by four
families or less on each story, and in any section of a class A dwelling
which is two stories or less in height and occupied by four families or
less on each story, a means of egress from an apartment may open
directly into a stair without the intervention of a public hall.