Ensure your cylinders and valves are tested regularly to prevent possible air leaks and ultimatley failure as in the case of this cylinder.
It was overdue a service. As you can see the oring is well past it’s best and has deteriorated to the point of it breaking into pieces. It is also worn to about 10% of it’s normal size and completely lost it’s ability to seal safely.
Diving cylinders should be tested every 30 months in the UK. Also every 15 months if used for Enriched air gases. Make sure your’s is safe to use for diving, have it inspected and tested on a regular basis.