Abstract: This invention relates to a method and apparatus for applying volatile substances, particularly microbicidal substances, to materials such as foods, pharmaceutical products and ingredients thereof for the purpose of achieving at least partial microbial decontamination and/or shelf-life extension. The volatile substance, which is preferably carbonic acid, acetic acid, hydrogen peroxide and mixtures thereof, are entrained in a carrier gas and preferably applied to the material at an over-pressure of up to 3 bar (2250 mm Hg) above atmospheric pressure.