Md. Code, Public Safety § 12–1103

A carbon monoxide alarm may be combined with a smoke alarm if the combined device complies with:

(1) this subtitle;

(2) Title 9 of this article; and

(3) American National Standards Institute (ANSI)/Underwriters Laboratories (UL) standards 217 and 2034 or ANSI/UL 268 and 2075.