Abstract: This invention provides an apparatus and method for processing produce to reduce microorganisms thereon by treating the produce in a treatment chamber. The treatment chamber comprises a produce receiver disposed in the treatment chamber, a means for providing a gas stream comprising chlorine dioxide and a carrier gas into the treatment chamber, a chlorine dioxide sensor in communication with the treatment chamber, and a means for controlling the concentration of chlorine dioxide in the treatment chamber. The method comprises exposing the produce to an atmosphere comprising gaseous chlorine dioxide and a carrier gas in a treatment chamber and can comprise controlling the concentration of chlorine dioxide in the treatment chamber, moving the produce in the treatment chamber during exposure to the gaseous chlorine dioxide, spraying water to remove the gaseous chlorine dioxide, and purging the treatment chamber to remove any residual chlorine dioxide.