Abstract: A dispersal unit for use in treating perishable goods in a storage volume to control microbial growth, the dispersal unit comprising: a housing; an airflow passage in the housing; an impeller for driving a flow of air through the airflow passage; a support for supporting at least one replaceable cartridge in communication with the airflow passage; and a vapouriser for promoting vapourisation of a volatile antimicrobial active material in a cartridge supported by the support to release an antimicrobial vapour from the cartridge into the airflow passage to be entrained in the flow of air and expelled from the airflow passage into the storage volume.