Humidification measurement is now feasible, but it is cumbersome and costly for routine use. The user therefore may rely on data supplied with the humidification device and obtained according to ISO standards. For comparison purposes it would be extremely helpful if both standards used to describe humidification properties quoted performance values in the same manner, preferably as moisture loss measured as milligrams of water per liter at the maximum tidal volume. The acceptable water loss should be between 0 and 7 mg/L water depending on the specific situation of the patient.