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Hydrogen explosions in sprinkler systems

This study analyzes the cause of two explosions that occurred during maintenance on a sprinkler system to examine the risk of such an explosion. In both incidences, the explosion occurred after the system was drained into the water‐collecting tank and shortly after the work began. Sprinkler systems in Korea generally use galvanized pipes to prevent corrosion and extend their lifetime. Zinc is the most common element used as a coating material. Although such a system is not usually perceived as dangerous, our study shows that it can contribute to a build‐up of hazardous factors, which ultimately can lead to accidents. As a common metal oxidation reaction, zinc produces hydrogen gas while oxidizing within the water‐filled pipes. Such hydrogen gas can become explosive when stagnating inside the water‐collecting tank as the sprinkler pipes are drained. In both explosion cases, the automatic water level control system of the water‐collecting tank is suspected to have acted as an ignition source for hydrogen gas explosion by electrical contact. By understanding these two cases, we can provide better safety standards for explosion protection for sprinkler systems that are already installed in buildings and those that will be installed in the future.