Sleeping gas

Marisa stopped when she heard hissing above her head. She looked up to see a vent pumping white smoke into the room.

She held her breath as she continued to pull the bars apart. She managed to make a big enough opening to get out of, but she was running out of air.

She went back for the painting, taking in one gulp of air. She grabbed it and headed back for the opening. Her vision swam but she had to take another gulp of air on the way...

Marisa passed out just as she reached the gate.