Maryland Code, Tax-General § 11-235

(a) The sales and use tax does not apply to the cleaning of a commercial or industrial building if the building is owned by a common ownership community or retirement community and used for:

(b) The exemption under subsection (a) of this section does not apply to the cleaning of a commercial or industrial building or the proportionate share of the building that is used for a purpose that requires the collection of the sales and use tax under this title.