Hydrogen release from a gas bottled in a R&D laboratory

A 50-litre standard hydrogen gas cylinder was temporarily placed and used in a laboratory. The hydrogen gas was used for a flame ionization detector (FID) in gas chromatography (GC) instrument.
The safety relief valve on the pressure regulator blew open and released of about 340 g of hydrogen into a laboratory. The gas cloud did not ignite so there was no injury or damage.

In Henriksen et al (see references) a full investigation is presented to verify the cause of leakage and estimate the gas concentration of the dispersion and gas cloud, including the modelling of a likely explosion. If the gas cloud had ignited, the explosion pressure would most likely cause significant structural damage.

The INITIATING CAUSE was the degradation and leaking of a pressure regulator.
The temporary safety setting of the lab functioned as designed, and the detector activated on hydrogen presence before further escalation.
However, due a misunderstanding within the organisation, a bigger hydrogen cylinder was installed than the one agreed during risk assessment. Moreover, the regulator had never been the object of an inspection and maintenance plan. All this suggests a ROOT CAUSE in shortcoming of operative and safety procedures.

hydrogen pressure regulator, 200 bar compressed hydrogen bottle,

The condition were abnormal because of the temporary decision to isntal compressed gas in a lab.

According to Henriksen et al. (see references), the were:
1. Under the abnormal condition of operation of the lab, the planned reduction of the total hydrogen quantity to a small 10 l bottle would have reduced the released hydrogen by 55% even in the case of complete depleted.

2. The presence of a hydrogen detector and alarm may have saved the laboratory from a severe accidental explosion. Without it, the whole hydrogen gas cylinder would probably have been released into the room, creating a 1.2 meters high gas cloud with 15 % stoichiometric hydrogen.

3. The age of the hydrogen gas regulator used was difficult to determine by reading the numbers printing on the back. The age was first established after contacting a supplier. This is an important information to determine the end of life of lab instrumentation.

4. Related to point 3., there is a need for regular maintenance/check of the gas regulators . Following the incident, a service has been established.

5. A pressure safety valve on the gas regulator is not a safety feature when the safety valve releases the gas into an environment that contains several ignition sources. To work as a safety feature the gas needs to be routed to a safe ventilation point. A similar event happened at a commercial facility in 05/03/2013, where a failure of the pressure safety valve occurred. One of the conclusions from the investigation was that if the safety valve shall function as a safety feature the gas needs to be released in a safe location.