CGH2 cylinder releasing full content in a laboratory

Two employees were changing hydrogen gas cylinders in an analytical laboratory. When removing the cap from the new cylinder, they heard a hissing noise and realised that the tank was leaking. After a quick attempt to shut off the tank, which was not possible because the cap was still mounted, they left the lab and notified the supervisor, who ordered the area evacuation and called the local fire department.
It was decided to allow the tank to vent until it was empty. After a time assessed enough for the cylinder to have released it content, the room was accessed with gas detectors, which did not revealed any presence of hydrogen.

The INITIATING CAUSE was the accidental opening of the cylinder valve during the installation in the laboratory. This was a mix of an improper manual action and the instructions not specifically prohibiting it.
The ROOT CAUSE was the absence of working tool to open the cylinder caps, which are infamously known to be difficult to unscrew. Moreover, the execution of the emergency actions revealed the need to improvement certain aspects of safety operative control and emergency management.

valve, wrench

This is the detailed emergency sequence:
(1) After checking that everyone was out of the lab, the supervisor paged all staff in the vicinity to immediately evacuate to the staging area.
(2) Facility management and ES&H management were notified about the situation, and they contacted the local fire department to respond to the site in case the venting gas was ignited.
(3) On their arrival, the first responders agreed with the facility management and the site safety officer to allow the tank to vent until emptying.
(4) The hydrogen gas supplier was called, but a specialist was unavailable at that time. Based on information from the hydrogen supplier's website and some basic estimates of the hydrogen release rate, facility staff determined when the contents of the tank would have been completely vented.
(5) It was decided that first responders would approach the lab in full bunker gear with Self-Contained Breathing Apparatus and a gas detector, to assess any gas present.
(6) Two first responders entered the lab and two were stationed as back-up. No hissing was heard and the detector confirmed that the cylinder had vented and the lab was clear of flammable H2-air mixture.
(7) The hydrogen cylinder was moved outside and secured and later returned to the supplier.

Compressed gas cylinder caps can be very difficult to open, due to rust developed in the threads. The employees were using the wench specifically designed to remove compressed gas cylinder caps. However, this tool often does not provide enough leverage to easily open the cylinder caps.
Therefore, all over the world, staff often reverse the wrench, pushing it through one of the cylinder cap openings to gain additional leverage on cylinder cap lids. In this case, this operation interfered with the cylinder valve.

The training program of the company and the written instruction of how to safely handle compressed gas cylinders did not prohibit using the valve cap wrench in the manner it was used.

Another lesson emerged from the evaluation of the emergency was that all controls, such as gas detection and ventilation speed were inside the laboratory and could not be assessed and/or activated from outside. This is a situation common to many analytical laboratories. Remote control and/or automatic interlocks should be considered during the initial safety design and regularly during operation, based on operative experiences of employees.

H2TOOLS reported the following corrective actions:
1. Obtain different wrench providing adequate torque on cylinder cap but not interfering with valve.
2. Train staff on how to use new wrench.
3. Loosening cylinder caps outside of the building before bringing the cylinders into the lab [Note of HIAD event validator: this measure should be accompanied with ensuring a safe transport, the fall of a cylinder without cap could damage its valve].
4. Move the hydrogen supply station outside of the building [Note of HIAD event validator: a no-compressed-gas-cylinders-inside is a policy often prescribed by companies safety rules and countries regulations].
5. Update job safety analysis sheet to reflect new cylinder handling procedures.
6. Improve evacuation [Note of HIAD event validator: in case of flammable gas releases, evacuation should be automatically triggered by visual and sound alarms reaching all staff, which should already know what to do].
7. Share lessons learned with other facilities.
8. Reinforce with staff the need to check offices, conference rooms, and rest rooms as they are evacuating to ensure that all staff are aware of the emergency.
9. Reinforce with incident commanders the need to ensure that formal written accountability is taken during an emergency.
10. Investigate the feasibility of relocating critical building controls outside of the analytical lab.