Abstract: The disposal of material containing infective microorganisms such as bacteria, fungi and viruses and more especially for the disposal of waste from medical facilities such as clinics and medical practices or the like may be performed in a simple and economic reliable fashion to provide satisfactory area coverage if the substrate is introduced into a container (1) able to be charged with ozone and exposed therein to the action of the ozone until the microorganisms are killed, after this the ozone is discharged from the container (1) and is converted to a lower valence level and the container (1) is then evacuated.