These valves are designed to be attached to tanks in order to prevent the buildup of pressure or vacuum. Adjustable models have opening pressure rated for 8-40 psi depending on size. As for vacuum, the Tassalini brand fixed at 0.01 bar (.145 psi, 0.29 in/hg) and generic brand ranges 0.3-0.9 bar (4-13psi, 8-26 in/hg), depending on size. Valves are not factory set to a value below the vessel max operating pressure, set point must be confirmed prior to use. Temperature Range: -10°C (-15°F) to +95°C (205°F).