Md. Code Ann., Transp. § 23-206.1

Notwithstanding any rule or regulation to the contrary and unless otherwise prohibited by federal law, any fire or rescue apparatus or ambulance owned or leased by a political subdivision of the State, or by a volunteer fire company, rescue squad, or volunteer ambulance company, that is registered as an emergency vehicle as defined in § 11-118 of this article, is exempt from mandatory inspections under this subtitle.