You can check with an attorney to be sure, but I would expect there to not be an expectation of privacy in a common hallway.
According to the internet---
"Video surveillance is a bit different than audio surveillance under Maryland law. It is legal in Maryland to use surveillance video in your home, including on your porch or lawn, without consent from the parties being recorded.
"However, it is illegal to use hidden surveillance cameras in places where people expect privacy—these places include bathrooms or dressing rooms. Deliberately using video to record people in their respective private residences or in a private place without their consent is considered unlawful in the state of Maryland."
It cites the Greater Baltimore Board of Realtors blog post from 3/27/19 entitled "Is it Legal to Record Audio or Video In Maryland without Consent?" --137.118.xx.xxx