A spirometer is a precision instrument designed to record the precise volume of air that is exhaled in to them. A calibration check should be carried out as part of a daily routine using a calibration syringe. A calibration syringe injects a known volume of air through the spirometer which should record a reading within 3% of this known volume. We sell a 3.0 liter calibration syringe that provides an accurate check for you, if your spirometer does not record within the 3% tolerance it will require re-calibrating.