A generator cell includes a high voltage assembly having a high voltage electrode, a low voltage assembly having a low voltage electrode, a barrier dielectric between the electrodes defining a discharge region for producing a reactive gas, and a welded seal joining the assemblies to create a permanently sealed chamber between the assemblies including the discharge region. The generator cell may have a gap in the discharge region of 0.005 inch or less. The cells may be modularly combined to form a reactive gas generator system.