30 CFR § 56.4603
Closure of valves
July 29, 2020
To prevent accidental release of gases from hoses and torches attached to oxygen and acetylene cylinders or to manifold systems, cylinder or manifold system valves shall be closed when—
(a) The cylinders are moved;
(b) The torch and hoses are left unattended; or
(c) The task or series of tasks is completed.