Maryland Code, Public Safety § 9-103

(a) This section applies only to new residential units constructed on or after July 1, 2013.

(b) At least one smoke alarm shall be installed in each sleeping room, in the hallway or common area outside of sleeping rooms, and in the hallway or common area on each level within a residential dwelling unit, including basements and excluding unoccupied attics, garages, and crawl spaces.

(c) If two or more smoke alarms are required within a residential unit, the smoke alarms shall be arranged so that activation of any one smoke alarm causes alarm activation of all other required smoke alarms within the residential unit.

(d) Each smoke alarm required by this section shall operate on an alternating current (AC) primary source of electric power with a battery backup or an approved alternate secondary power source.

(e) In one- and two-family dwellings, a smoke detector installed as a part of an approved household fire alarm system is an acceptable alternative to the AC powered-battery backup smoke alarm required by this section, if the smoke detector is installed and located as specified in subsection (b) of this section.

(f) A smoke detector installed as a part of an approved fire alarm system is an acceptable alternative to the AC powered-battery backup smoke alarm required by this section, if the smoke detector is installed and located as specified in subsection (b) of this section.