A method for decontaminating a biological safety cabinet with a falling film evaporator, the method comprising the steps of: providing a falling-film evaporator within a cavity of the biological safety cabinet, said evaporator having a housing defining a cavity, a lower end of the housing being formed to define a sump dimensioned to hold a predetermined quantity of liquid decontaminant and an evaporation element disposed in said cavity, conveying a carrier gas through said cavity of said housing wherein said carrier gas is conveyed along said outer surface of said evaporation element to evaporate said liquid decontaminant, thereby forming a mixture of said carrier gas and said vaporized decontaminant; and exhausting said mixture into said cavity of said biological safety cabinet to decontaminate articles and surfaces in said cavity of said biological safety cabinet; wherein any liquid decontaminant on the outer surface of the evaporation element that does not evaporate in the air flows downwardly to the lower end of the evaporation element and collects in the sump; conveying said liquid decontaminant from a source of liquid decontaminant to said evaporation element such that said liquid decontaminant flows along a surface of said evaporation element; the method comprising the characterizing steps of: the evaporation element having an open upper end and a closed lower end and defining an internal cavity, a conduit fluidly connecting said internal cavity to said sump, a sump pump being disposed in said conduit; activating said sump pump to convey metered amounts of a liquid decontaminant from the sump to the internal cavity of the evaporation element such that said liquid decontaminant overflows the open upper end of the evaporation element and flows downwardly along an outer surface of said evaporation element. providing a falling-film evaporator within a cavity of the biological safety cabinet, said evaporator having a housing defining a cavity, a lower end of the housing being formed to define a sump dimensioned to hold a predetermined quantity of liquid decontaminant and an evaporation element disposed in said cavity, conveying a carrier gas through said cavity of said housing wherein said carrier gas is conveyed along said outer surface of said evaporation element to evaporate said liquid decontaminant, thereby forming a mixture of said carrier gas and said vaporized decontaminant; and exhausting said mixture into said cavity of said biological safety cabinet to decontaminate articles and surfaces in said cavity of said biological safety cabinet; wherein any liquid decontaminant on the outer surface of the evaporation element that does not evaporate in the air flows downwardly to the lower end of the evaporation element and collects in the sump; conveying said liquid decontaminant from a source of liquid decontaminant to said evaporation element such that said liquid decontaminant flows along a surface of said evaporation element; the method comprising the characterizing steps of: the evaporation element having an open upper end and a closed lower end and defining an internal cavity, a conduit fluidly connecting said internal cavity to said sump, a sump pump being disposed in said conduit; activating said sump pump to convey metered amounts of a liquid decontaminant from the sump to the internal cavity of the evaporation element such that said liquid decontaminant overflows the open upper end of the evaporation element and flows downwardly along an outer surface of said evaporation element.