Methods for disinfecting or sterilizing an article are provided. One method includes vaporizing a solution comprising a biocide in a solvent having a first biocide:solvent ratio, directing a flow of the vapor to a first side of a membrane directing an alternate flow of a gas to a second side of the membrane to increase the first biocide:solvent ratio on the first side to a second biocide:solvent ratio greater than the first biocide:solvent ratio thereby producing a concentrated vapor on the first side of the membrane, and contacting the article with the concentrated vapor for a time sufficient to disinfect or sterilize it.
