Non-condensible gases result from the water from which the steam is generated. These gases will usually be air, though carbon dioxide may be present, caused by certain water treatment processes, typically water softeners. This is exacerbated by excessive aeration that can exist in many pharmaceutical water treatment plants where water is constantly recirculated and sprayed into the top of storage vessels. The effect of such gases being present in the steam supply to a sterilizer can be the same as air, none sterilization of the volume they occupy.
