Deflagrations of H2–air and CH4–air lean mixtures in a vented multi-compartment environment

The use of hydrogen as an energy carrier for the future is conditioned by its safety. Hydrogen is commonly and incorrectly perceived as being a more dangerous gas than methane, since the latter is widely used and thus considered to be acceptable. The paper analyses deflagrations of H2/air and CH4/air mixtures at low concentrations (close to the lower flammability limits) and, in particular, focuses on the phenomenology and dangerous aspects of this kind of combustion. The related possible accidents involve closed environments (garages, laboratories, service rooms, internal volumes of buses and cars, etc.) where ignition sources are present. In these cases, combustion probably takes place as soon as the fuel concentration reaches the lower flammability limit.