What is the function of a tank vent in a heating oil tank?

The function of a tank vent in a heating oil tank is primarily to allow air flow during the filling and emptying processes. When the tank is being filled with heating oil, the vent provides an outlet for the air that is displaced by the incoming oil. This is crucial because without proper venting, pressure could build up inside the tank, potentially leading to a dangerous situation or even causing damage to the tank itself.

Similarly, when oil is drawn from the tank for use, the vent allows air to enter the tank to replace the volume of oil being removed, ensuring that there is no vacuum created that could impede the flow of oil. This airflow mechanism is vital for the safe and efficient operation of the heating oil tank.

While other options mention various aspects of a heating oil tank's operation or structure, they do not address the specific role of the vent, which is central to maintaining appropriate air pressure within the tank during the fill and draw processes.