The gases temperature supplied to a patient when the patient is undergoing treatment such as oxygen therapy or positive pressure treatment for conditions such as Obstructive Sleep Apnea (OSA) or Chronic Obstructive Pulmonary Disease (COPD) is often measured for safety and to enable controlling of the humidity delivered to the patient. The invention disclosed is related to measurement of properties, particularly temperature (thermister 23), of gases flowing through a heated tube (3), supplying gases to a patient, which utilises the heating wire (21, 28) within the tube.