Sunpentown manufactures household appliances such as humidifiers and air conditioners. Humidistats are used in a number of devices including dehumidifiers, humidifiers, and microwave ovens. Some evaporative coolers may also serve as humidifiers in the heating season. Medical ventilators often include humidifiers for increased patient comfort. Ultrasonic humidifiers are frequently used in aeroponics, where they are generally referred to as foggers. Examples include microwave ovens, toasters, humidifiers, food processors and coffeemakers. Some CPAP machines have other features as well, such as heated humidifiers. Electronic humidifiers are also available, although usually reserved for very large humidors. This way electronic humidifiers can maintain a much more stable humidity level than passive humidifiers. The mill would have had humidifiers and a sprinkler system. Passive respiratory gas humidifiers are independent from any external energy source or external water supply. These types of humidifiers are usually noisier than others. In such cases, the application of active respiratory gas humidifiers is recommended. Printers and paper manufacturers use humidifiers to prevent shrinkage and paper curl. Further applications include&colon; humidifiers, sonar, medical ultrasonography, burglar alarms, non-destructive testing and wireless charging.