ISO 27895:2009 specifies methods for the leak testing of vacuum valves used for control of gas flow or vacuum pressure in a vacuum system.It is applicable to vacuum valves that can be closed to leak rates less than 1 x 10^-5 Pa m³/s for trace gas. The methods employ a sealing arrangement for the valve body, which is also specified in ISO 27895:2009. The methods are suitable for the verification of valve specifications.

A valve leak rate less than the nominal leak rate specified by the manufacturer during and after the operation enables the specification of such valve operating conditions as operating pressure range, permissible pressure difference between ports, bake-out temperature or operating temperature, and life cycle.