A pressure and vacuum relief valve is a pressure equalization valve for impermissible pressure and vacuum in a closed system.
A pressure or vacuum relief valve is installed in vent lines of vessels and equipment and enables the equalization of overpressure or underpressure. The function depends on which connection socket of the valve is connected to the tank. When connected to a bleed line, the valve compensates for overpressure; when connected to a vent line, it compensates for underpressure.
