"Heating vents" refers to the openings or passageways in a building that allow warm air from a heating system to flow into different rooms, effectively distributing heat throughout the space. Full definition
As well as having to strip off lining paper, there were ugly, exposed pipes to box in and defunct central heating vents in the walls and ceilings to cover and plaster over. (idealhome.co.uk)
Two sets of heat vents protect your hands and keep the noise levels down. (geekwrapped.com)
Many of these images depict paintings hanging over heat vents, chair rails, or in poor lighting conditions. (clyffordstillmuseum.org)