Breather or direct-acting vacuum pressure relief valves protect enclosed containers against rupture or damage. Available in various types, including vacuum-only, pressure-only, and combination valves. Pressure relief valves are available with flanged outlets or outlets vented to the atmosphere. Tank valves are used in bulk-enclosed containers and tanks to minimise evaporation loss and prevent excessive vacuum or pressure build-up.

Vacuum relief valves release trapped air pockets and prevent permanent physical damage or deformation of large-capacity storage containers. By installing valves within the tanks, system unbalances, and container damage can be avoided. These valves have springs or weight pallets to regulate vacuum and pressure levels. Most valves combine spring and pallet systems, where the spring section is used for pressure settings, and the pallet is used for adjusting vacuum settings.