N.Y.C. Admin. Code § 27-2043: § 27-2043 Locks in dwelling unit doors.

a. The owner of a dwelling shall provide a key lock in the entrance door to each dwelling unit and at least one key. In a class A multiple dwelling such door shall be equipped with a heavy duty latch set and a heavy duty dead bolt operable by a key from the outside and a thumb-turn from the inside.

b. Each dwelling unit entrance door in a class A multiple dwelling shall also be equipped with a chain door guard so as to permit partial opening of the door.