Sterilisation kills germs and spores found on the surfaces of objects. Various methods for sterilising objects exist, such as the use of hot-air sterilisers or autoclaves. Hot-air sterilisers expose objects to a dry heat of 180°C or more for at least 30 minutes. However, this procedure may cause damage to the materials. Autoclaves, on the other hand, kill germs through moist heat, for example, 120°C – 135°C under vapour pressure. The materials remain unaffected. The medical sector in particular uses this method for sterilising instruments, surgical clothes, and other objects. Another sterilisation method is based on irradiation or fumigation using ethylene oxide or formaldehyde.