A leak occurred at a of a liquid withdrawal valve of a liquid hydrogen storage tank. The hydrogen escaped at the flange between the valve body and the upper part of the valve (flange with tongue and groove). 40 kg of hydrogen were lost.The accidental release was due to the use of bolts different from those prescribed. By using the wrong ones (old bolts), the bolt material was able to flow at the specified tighteningtorque. This meant that there was insufficient tightening torque, which led to a leak.

The event occurred at the hydrogenation unit of a pharamceutical company. 145 kg of hydrogen were released the atmosphere at the gas circulation pump, due to a maintenance error . A specialist company (third-party company), had replaced the cylinder head of pump, but during assembly they did not re-isntalled the prescribed temperature sleeve for the thermometer (the temperature sleeve is the pressure-bearing element).

The accidental hydrogen release occurred when testing the storage system connected to a PEM electrolyzer. The leak test consisted in filling the storage with hydrogen at step-wise increase of pressure. After the step at 3 bar (0.3 MPa), which did not reveal any leak, the storage was pressurised up to 5 bar (0.5 MPa). At that moment a hissing sound occurred from the storage at the outside of the building indicating a leak.

The incident involves a gas booster provided by a manufacturer. This device is used in the experimental platform of the project to raise the pressure in pipelines from 60 to 80 barg (from 6 to 8 MPa), allowing the gas to flow in a close loop. After 5 weeks of operation, a critical gas leakage through the vent port was detected.At the moment of the incident, the compressor was working with a mixture of hydrogen and methane (H2/CH4 blend 20/80 %v/%v). The booster was sent to the manufacturer for inspection and reparation. Severe damage in the seals of the vent port was found.

A fire broke out on a transformer transforming 225,000 V into 15,000 V in a metallurgical plant. This transformer supplies electrical power the site and to a neighbouring factory. In the following three hours, staff brought the fire under control with CO2 extinguishers, the internal emergency plan was activated, and the firefighters ventilated the premises and took readings of the flames using a thermal camera. Meanwhile, however, the shutdown of the electrical installation caused the stop of the operation of an electrolysis unit using zinc sulphate.

This near miss occurred at an airport's hydrogen refilling station. At 7:35, a hydrogen leak was detected by hearing whistles in the near of a pipe. The operators warned the airport firefighters ten minutes later. Upon their arrival, the firefighters set up a security perimeter of 150 m around the installation. The station is located on the border between the public space and the private space and was surrounded by a fence with a gate accessible only by a code unknown to the emergency services.

A cryogenic hydrogen laboratory had a power outage. The cryogenic hydrogen storage was no longer being cooled, therefore temperatures and pressures within the storage system started rising. There were several relief devices on the system, one with a set point of 150 psi (approximately 1 MPa) and a second at a set point of 165 psi (1.1 MPa). The system was monitored by site personnel so that when the hydrogen pressure increased to 120 psi (approximately 0.5 MPa), a manual vent was opened. However, the manual vent rate was not able to control the rising pressure.

A hydrogen safety sensor went into alarm at a hydrogen demonstration facility. The early morning temperature was near freezing and there was a trace of precipitation on exposed surfaces. Upon further inspection following the sensor alarm, a 3,500 psig (approximately 24 MPa) stationary storage vent was found to be releasing hydrogen through the PRD vent stack (PRD = Pressure Relief Device). The alarming sensor was at an adjacent building but responded to hydrogen 20 yards (18 m) downwind from the vent location. The vent release location is 10 feet (3 m) above ground level.

The accident occurred at a production, distribution and storage station for hydrogen city busses. After filling the hydrogen cylinders of a bus, the hydrogen detection system of the bus triggered an alarm. The site technician pushed the emergency button and the station was put in safety mode. The technician in charge of filling disconnected the hydrogen hose that connects the station to the bus. The maintenance manager of the bus manufacturer was alerted and arrived 20 minutes later and evacuated the personnel. They closed the valves of the on-board storage system.

During the shipments of incinerator bottom ash, flammable gasses including hydrogen generated and caused two explosions. The first explosion was in the forecastle store and the second in the cargo hold.The vessel was loaded with a cargo of 2333 tonnes of unprocessed incinerator bottom ash. The chief engineer, who was inside the forecastle store at the time, suffered second degree burns and was airlifted to a nearby hospital.