The fire took place during maintenance works in one out of the three gas extractors of the coke process line. Main cause was displacement of a flange which allowed the entrance of flammable mixture gas (methane, carbon monoxide hydrogen and benzene) which ignited probably due to electrostatic spark. According to the ARIA report (see references) total quantity of gas released was 62 400 m, consisting of 11,7 t CH4, 0,98 t C6H6, 5,1 t CO and 3,4 t H2.During maintenance works, gas extractors were usually isolated and kept under continuous flow of N2.

Hydrogen fire at a chlorine chemical production plant (Seveso-classified)Hydrogen ignited in a chlorine electrolyzer unit. The facility was shutdown. The staff of the unit, present on site, triggered the fire alarm and put the installations in a safe state. The fire was extinguished after the start of the intervention of the internal fire brigade.According to the ARIA report (see reference), a variation in electrolyzer pressure was caused by the shutdown of a tank due to the malfunction of its level detection gauge.

Hydrogen explosion at a chlorine chemical production plant (Seveso-classified) The plant had been shut down for two weeks, and maintenance works were ongoing. Two subcontractor employees were cutting a purge pipe on a hydrogen manifold in the chlorine electrolysis room while a manufacturing operator was purging the brine circuit (brine is used as a raw material in chlorine production).

Release from a compressed storage of an optics component plant The leak was observed on the hydrogen storage consisting of 19 racks of 16 cylinders each. Rescue teams set up a security perimeter and a specialized company inspected the leak.The activity of the establishment were interrupted during the night and resumed the next morning.

During maintenance work on a gas pipeline carrying hydrogen , a worker hears a leak at about at a bridge. The operator measures an concentration of 3% of the low flammability limit at few centimetres from the leak, and no detection beyond 25 cm. The area was highly ventilated. The technicians secured the area, isolated the section five hours later and started the controlled gas release. after two additional hours the pressure had reduced to zero and they started the nitrogen inerting. The pipe was repaired the next day.

A leak of 700 l of gaseous hydrogen was detected around on a connection of a rack of cylinders on a trailer truck, in aircraft plant (classified Seveso, lower tier).

Fire in chemical plant (Seveso-classified)The fire developed at the top of the flare stack of a during a violent thunderstorm.The flare stack is used to discharge hydrogen produced by the restarting of chlorine electrolysis cells. The fire was ignited despite steam and nitrogen had specifically were injected to prevent it from occurring. The sites firefighters cooled the flare stack while the technicians turned off the electrolysis cells to cut off the hydrogen feeding the flames.

A leak occurred on a rack containing 12 cylinders of hydrogen (50 l at 200 bar each) delivered by a lorry inside the fenced storage area of a bulb manufacturing plant. The plants safety manager closed access to the area, had the other lorry drivers on the site cut off their ignitions, and made them evacuate. The firefighters tested the air with an explosimeter and stopped the leak by closing the gate valve located on the outside of the rack. The valve was used to transfer hydrogen from the cylinders to their points of use. The rack had been delivered by a crane lorry.

Explosion in a fine organic chemical plant (Seveso classified )The event occurred during the cleaning of a reactor. At the completion of a batch manufacturing of a soft reducing agent, an operator was rinsing the 3000-litre reactor first with a solvent and then with a water jet . Noticing a smoke release, they informed their team leader, who opened the manhole of the reactor. This action caused a flash type explosion at the reactor entrance. According to the ARIA report (see references), the rinsing water reacted with sodium hydride (NaH) residues on the reactor walls to form hydrogen.

The event occurred in an atmospheric pressure tank storing effluents. The plant was in the production phase. The head of the overfill prevention valve located at the top of the tank was thrown a distance of 77 m. The tanks shell was deformed (curved downward) but not leaking. Employees noted a noise similar to the opening of a valve, and a low-pressure alarm in the tank appeared in the control room, despite the fact that the level and temperature were normal.