The Hygiena units self-calibrate each time they are turned on. It exceedingly rare that a unit goes out of calibration.
However, if a unit has been sitting idle for an extended period, or potentially miss-treated, or should you need to prove the Hygiena unit is in spec for audit purposes the calibration control kits can be purchased. They have an unrefrigerated shelf life of 5 years with unlimited uses.
Comprised of a negative and positive rod, these guarantee that the Ensure touch is producing the most accurate results possible.