A leak of hydrogen, methane and hydrogen sulphide from a pipe in a refinery

The leak occurred on a process pipe of a pressurized at 17 bar and located 3.5 m from the ground The gaseous mixture composed of hydrogen, methane and hydrogen sulphide (density: 0.6) was released to the atmosphere.
The operator evacuated a hundred employees, stopped production and put the establishment in the safe mode.
The emergency plan is triggered. Water curtains are put into action and measurements of toxicity and explosimetry are carried out.
After a hour the pressure in the pipe reduced 0.5 bar and the measurements of toxicity and explosimetry in the ambient air returned to satisfactory level. The emergency plan was terminated.
Public firefighters are on site but did not intervene.

pressurised gas process pipe (17 bar) located 3.5 m from the ground