An apparatus for generating a flow of reactive gas for decontaminating a material, surface or area, comprises a first electrode member comprising a first plurality of conductive surfaces and a second electrode member comprising a second plurality of conductive surfaces. The second electrode member is arranged in spaced relationship with the first electrode member to define a reactor channel. The conductive surfaces are exposed to the reactor channel so as to form air gaps between the first plurality of conductive surfaces and the second plurality of conductive surfaces. An air blower generates a flow of air through the reactor channel. An electric pulse generator repetitively generates voltage pulses between the first and second electrode members so as to produce glow discharges in the air gaps between the conductive surfaces of the first plurality and the conductive surfaces of the second plurality, the voltage pulses being generated at time intervals less than 1 millisecond and voltage pulse duration less than about 500 ns, the glow discharges being adapted to transform part of the flow of air into reactive gas. An output section delivers the reactive gas from the reactor channel to a sample or region to be decontaminated or treated.