永久气体 meaning in Chinese

permanent gas

Rules for filling of permanent gas cylinders
永久气体气瓶充装规定
Safety specification for filling station of permanent gas cylinders
永久气体气瓶充装站安全技术条件
Transportable gas cylinders - battery vehicles for permanent and liquefied gases excluding acetylene - inspection at the time of filling ; german version en 13385 : 2002
可运输的储气瓶.永久气体和液化气体
Transportable gas cylinders - cylinder bundles for permanent and liquefied gases excluding acetylene - inspection at time of filling ; german version en 13365 : 2002 a1 : 2005
可运输的储气瓶.永久气体和液化气体