30 C.F.R. § 250.206
A barrier or barrier system is any engineered equipment, material, component, or assembly that is installed to contain a hydrocarbon pressure source(s) to prevent harm to people or the environment. BSEE only recognizes barriers that are either permanently or temporarily installed, pressure controlling, and/or pressure containing. You must be able to activate pressure controlling barriers on demand (i.e., closed by an operator or automated safety system). You must function test and pressure test any pressure controlling barriers or barrier systems to defined acceptance criteria that can be repeated. You must pressure test any pressure containing barrier or barrier system to defined acceptance criteria that can be repeated.
30 C.F.R. §250.206