Apparatus for concentrating a nebulant comprising a nebulant flow conduit anda counter-flow conduit, or preferably, a plurality of alternating nebulantflow conduits and corresponding counter-flow conduits eg in layered or coaxialarrangement, and wherein at least a portion of the nebulant flow conduit andsaid counter-flow conduits define respective opposed sides of a gas permeablemembrane. In use a nebuliser is in communication with the nebulant flowconduit and the nebulant flow and counter-flow are in the same or oppositedirections and act to concentrate the amount of active in a droplet eg from35wt% to 60wt% hydrogen peroxide in water to disinfect and/or sterilize anarticle.
