Detonation in a safety cabinet containing hydrogen cylinders

The safety cabinet with compressed hydrogen was located in a laboratory and used to supply hydrogen to an experimental facility. The safety cabinet was equipped with exhaust extraction. Due to a leak, technical assistance had been requested from the fire department. The head of laboratory shut off the electrical supply to the laboratory. Measurements showed that there was no potentially explosive atmosphere in the laboratory room.
The plan of the fire department personnel was to open the door of the safety cabinet and close the valves of the gas cylinders
While they were still putting on their protective equipment, the plant supervisor decided to purge the cabinet by blowing carbon dioxide into it from a fire extinguisher into the air intake aperture.
It followed and immediate detonation then which destroyed the safety cabinet.

[Note of HIAD event validator: date is also approximated because the source of this event, DECHEMA database, provides only the year of occurrence].

The INITIATING CAUSE of the hydrogen leak was a side connection on one of the gas cylinder valves, which had not been tightened sufficiently.
Its seal
had settled over the course of several days and was no more tight.
The hydrogen started leaking into the cabinet out, forming a potentially explosive atmosphere despite the exhaust extraction inside the safety cabinet.
The explosion was caused by the action of blowing into the cabinet carbon dioxide. It caused d an electrostatic charge which ignited the explosive atmosphere inside the cabinet.

safety cabinet; compressed hydrogen cylinders; laboratory;

The leak occurred because of the relaisation of an improper valve connection, days before the event.

The safety cabinet was destroyed.

The lesson learnt according to DECHEMA database [event no. 2007/01]:
(1) Prevention of leaks: gas supply installations are to be planned, assembled and checked by specialized personnel. Leaks checks must occur at regular intervals. Laboratory personnel must be instructed and provided with practical training in the handling of gas supply installations.
(2) Prevention of ignition hazards:
(2a) the laboratory personnel must also be instructed in handling extinguishing equipment. According to the German Professional Association Rules (BGR) 132, Section 3.3.2, fire extinguishers and fire extinguishing systems with extinguishing agents (e.g. carbon dioxide or extinguishing powder) which become electrically charged on dispensing should not be activated in the presence of a potentially explosive atmosphere.
(2b) If the fire department is called in, the required measures are to be directed exclusively by the head of the fire department team.