Safety Relief Valves / Blow-Off Valves WITT safety relief valves (blow-off valves) protect against overpressure by venting excess gases from pipelines, gas receivers and other equipment. The spring-loaded, direct-acting safety relief valves (blow-off valves) are suitable for individual opening pressures from 5 mbar to 45 bar (approx. 0.07 to 1 435 psi). The compact size allows easy installation in any orientation. A dust cap protects the safety relief valves (blow-off valves) against dirt. WITT safety relief valves (blow-off valves) are available in brass or stainless steel, as a ventable version, and with or without condensation outlet.