ATEX, explosion proof and working with flammable gases like Hydrogen

With knowledge of process parameters such as temperature or quantity of the flammable substance, the possibility of the formation of an explosive atmosphere can be assessed. For example, if the process temperature is well below the flash point of a flammable liquid or the amount of flammable substance does not allow the system to reach the lower flammability limit, an explosive atmosphere cannot form. Substance properties such as upper and lower flammability limits or flash point can be found in substance databases such as the GESTIS database of the Institute for Occupational Safety and Health of the German Social Accident Insurance. Various measures can be taken to prevent the formation of an explosive atmosphere. One general method is to ensure that the process allows the flammable substance to be replaced by a less harmful substance. Substitution is not always possible. For processes in a reactor system, replacement of oxygen and air with inert gases such as nitrogen, argon, or carbon dioxide is a sufficient means of preventing explosive atmospheres. When operating under conditions that are below the oxygen limit concentration, the system cannot form explosive atmospheres. These concentration limits can be achieved in reactor systems either by sufficient purging of the system or by multiple cycles of evacuation and refilling with inert gas.

To avoid explosive atmospheres in the vicinity of the reactor, adequate air circulation is recommended. This will ensure that the environment remains below the lower flammability limit. Prior to any experiment, it is strongly recommended to perform a leak test and ensure that the rupture disc is connected to the exhaust system via a gas hose. The permissible leakage rate of 0.5 bar/h is the most important source of flammable substances in the vicinity of the reactor. A fume hood with sufficient air flow can prevent the formation of an explosive atmosphere around the reactor and ensure safe working conditions. If the formation of an explosive atmosphere cannot be prevented, ATEX-certified equipment is used and an explosion protection document must be prepared. To improve occupational safety, the ATEX Directive (Atmosphères explosibles) 2014/34/EU came into force in April 2016. The ATEX Directive regulates the use of equipment and protective systems in potentially explosive atmospheres.