In this section the following words have the meanings indicated. “Confined space” means a space that, by design: has limited openings for entry and exit; and is subject to: the accumulation of a combustible agent; an accumulation of a toxic agent; or a deficiency of oxygen. “Confined space” includes: a basin; a bin; a degreaser; a duct; a pipeline; a pit; a sewer; a silo; a tank that is enclosed or has an open top; a tub; a tunnel; a vat; a process vessel; or a reaction vessel. “Maintenance work” means cleaning, inspection, maintenance, painting, repair, servicing, or other similar work. A person described in § 5–101(d)(2)(ii) or (iii) of this title may not allow or cause an individual described in § 5–101(c)(2)(iii) or (iv) of this title to do maintenance work in a confined space, unless the Commissioner: grants written authorization based on a satisfactory showing that work practices in effect will protect the health and safety of the individual; or in accordance with Subtitle 3 of this title, passes an order for a variance. This subsection applies only to an employer who is a subcontractor. Each subcontractor who, under an original contract or subcontract, is to do maintenance work in a confined space shall give the Commissioner: at the commencement of the maintenance work, oral notice of the maintenance work to be performed; and within 24 hours after the oral notice, written notice of the maintenance work.