The HSE have recently issued a safety alert about certain aluminium cylinders being subject to sustained load cracking (read: exploding under pressure):
The bulletin goes into how to identify the cylinders which are affected. A good rule of thumb however is any cylinder manufactured between 1963-1995 should be checked by an IDEST centre with visual eddy testing equipment.
If you are in possession of a cylinder which is made from the HE30/AA6082 or AA6351 alloys you should remove from service, release any contained gas in a controlled manner and quarantine it until it can be inspected.
Disclaimer: The information in this post is true and complete to the best of our knowledge. All recommendations are made without guarantee on the part of the author or Obsequio Ltd. The author and Obsequio Ltd. disclaim any liability in connection with the use of this information.