Cal. Code Regs. tit. 8 § 3306
Pressure vessels or other containers shall not be crushed, sheared, baled or otherwise processed for salvage until the employer has made certain that such vessels or containers do not contain hazardous substances or pressures in quantities which would render them unsafe for such salvaging operations. No attempt shall be made to open closed pressure vessels or containers of unknown contents until adequate precautionary measures have been taken to eliminate risk of injury to employees. Such precautionary measures may include rupture or perforation of the vessels while they are protected by barricades, enclosures or isolation.
NOTE: Certain cylinders and vessels, after passing their useful life, are destroyed by the owner of the vessel in such a manner that it can be resold for salvage purposes and can be crushed, sheared, melted or otherwise processed safely. (Some closed pressure vessels and containers may be safely disposed of by burying in the earth rather than by attempting to salvage them.)
Cal. Code Regs. Tit. 8, § 3306