Autoclaves are mainly used for steam pressure sterilization of culture media, medical instruments, surgical linen, swabs and the like. Autoclaving as a sterilization method is performed under moist heat. Moisture mainly makes the spores of bacteria swell, thus they are less resistant than in dry heat. The procedure is divided into four sections. The first section is the rising time, during which the interior of the autoclave is vented, i.e. the air is removed and replaced by saturated steam. Air removal is generally done by the gravitational process, which means hot steam rises and displaces the cold air. This process is checked by a thermometer inside the autoclaves. Once 100 °C has been exceeded at the coldest point in the working chamber, the venting process is complete, and a valve closes the working chamber in a pressure-tight manner. This allows the preset kill temperature (often 121 °C) to be reached. After this, the equilibration time begins, after which the goods to be sterilized also reach the required temperature at each point, and then the actual sterilization phase (sterilization time) begins. Which duration is chosen depends on the sterilization temperature, the type of autoclave and the microorganisms to be destroyed. For successful sterilization, the entire room air (atmosphere) must be replaced by steam.