(4)Every cylinder containing compressed gas shall have its valve securely closed so as to prevent leakage. Valves fitted to the cylinders containing Liquefied Petroleum Gas and highly toxic gases like Boron trifluoride, Carbon monoxide, Fluorine, Hydrogen chloride, Cyanogen chloride, Chlorine trifluoride, Hydrogen cyanide, Hydrogen fluoride, Hydrogen sulphide, Methyl bromide, Nitrogen tetraoxide, Chlorine, Ammonia or Sulphur dioxide shall be provided with security nut on the outlet to act as a secondary means of safeguard against leakage of gas.
