Screw them and their tags..
All compressed gas cylinders are considered dangerous because they contain gas under pressure. The cylinder’s valve can easily be damaged by falling or striking another object; something that could create a rocket out of an ordinary cylinder. The TDG Regulations [Section 5.4] say only that the cylinders/containers shall be loaded safely and securely stowed during transport. There is no direction as to how it should be done. In addition, CSA Standard B340 [referred to in Section 5.10(1)(a)(i)] requires that any gas with a liquid phase (for example, propane which is liquefied, or acetylene, which is dissolved in acetone), must be transported upright so that the safety valves are in contact with the vapour space and not the liquid.
"a welder must have banged his wife"