At the start of production on filling line B of an aerosol and bulk chemicals formulation and conditioning plant, there was a blast at around 12.20 pm in a gas transfer pipe containing nitrous oxide (N2O) and pentane. In the filling unit, a primary overpressure effect caused this pipe to rupture, upstream of the last transfer valve and at the top of the gas filter. The blast and the rupture caused a secondary overpressure effect in the filling unit, causing part of the suspended ceiling to fall (rock wool slabs) and the unit’s access doors to open. The employee present was not injured. A fire with a very pale coloured flame started where the filter door located on the pipe ruptured. The amount of materials involved was low. The automatic dual detection of flames and smoke in the second following the pipe rupture activated the controls on line B (shutdown of the unit’s filling machine, automatic closure of the compressed air supply valves, cutoff of the unit’s ventilation system, shutdown of all of the line’s equipment, activation of the siren and evacuation warning light, etc.), shutdown of all conditioning lines (identical controls with the exception of maintenance of the ventilation system) and transfers from the LPG park (shutdown of all transfer pumps, closure of automatic valves at the bottom of the tank and on the transfer pipes). The sprinkler system was activated automatically after 20 s: the fire was extinguished within a few seconds. At around 12.30 pm, the production staff were evacuated. 900 l of fire extinguishing water was recovered for destruction, and the filling unit and conditioning workshop were cleaned. The unit’s equipments were inspected before the resumption of safety systems (explosimetric detection, etc.)

The outbreak of fire in the piping was linked to the presence of the pentane/N2O mixture. Measures were considered such as, the banning of combustible/oxidising mixtures, creation of a specific N2O line equipped with a foolproof device, staff training, updating of the work instructions, and carrying out automatic safety fallback interventions on production tools easier (installation of automatic valves to isolate the pipe during activation of the safety controls).