<p>- 19 The present invention provides for an improved method of determining a water out condition in a humidified gases supply apparatus. The method includes a two step process including a primary determination of a water out condition and a secondary determination of a 5 water out condition. This primary determination is made during observation of the normal operation of the apparatus. During the secondary determination the method takes temporary control over the humidifying part of the apparatus. The secondary determination confirms or contradicts the primary determination. Monitor System Conditions 1050--- 1010 Do system conditions indicate N possible water out condition? Take control of heater power supply Monitor heater plate Temperature 1100 Does heater plateN temperature indicate aN water out condition? Provide output of a water out condition F G R Reduce or remove power to heater I</p>
