Delivered air should have a dew point lower than the operational temperature of the cylinder, which is generally above 0°C when immersed, but can be colder during transport. Air temperature is also decreased during expansion through the regulator when in use, and when this temperature is low enough for the condensate to freeze, it can lock up the moving parts of the regulator and cause a free flow, known as internal icing. Correct back-pressure also provides relatively even loading of the compressor stages, which reduces vibration caused by imbalance, and extends the compressor service life.