Detection of deposits in steam humidifiers

A method for determining whether a tank heater humidifier requires cleaning, the method comprising:

• (i) providing a tank having a fill valve for filling the tank with water, a drain valve for draining water from the tank, and a heater for heating water in the tank to produce steam;
• (ii) providing one or more sensors configured to detect the level of water in the tank, the one or more sensors being configured to detect water at a first level and a second level, where the first level is lower than the second level;
• (iii) determining whether water is at the second level in the tank of the humidifier, and if not, opening a fill valve until water is at the second level;
• (iv) opening the drain valve;
• (v) starting a timer measurement when the water falls below the second level in the tank and stopping the timer measurement when the water falls below the first level in the tank;
• and
• (vi) determining whether the humidifier requires cleaning based on the timer measurement.