Md. Code, Environment § 7–229

A person who is called on for assistance in an emergency has the immunity from civil liability or penalty described under § 5-617 of the Courts and Judicial Proceedings Article as a result of assistance or advice rendered in:

(1) Mitigating the effects of an actual or threatened discharge of a hazardous substance or material;

(2) Preventing a discharge of a hazardous substance or material;

(3) Cleaning up a discharge of a hazardous substance or material; or

(4) Attempting any of the acts in this subsection.