HVAC stands for heating, ventilation and air conditioning. Or alternatively, heating, ventilating, and air conditioning.
It refers to the different systems, machines and technologies used in indoor settings such as homes, offices and hallways, and transportation systems that need environmental regulation to improve comfort. For example, HVAC technicians would be hired to create the ideal environment in a subway or bus. They would also be hired to repair and install heating and air-conditioning systems in a new home that was being built, or to regulate the humidity level of an office.