drive circuits. Safety Ultrasonic cleaners can produce irritating, high-frequency noise and hearing protection may be needed in case of continuous exposure. It is recommended to avoid using flammable cleaning solutions because ultrasonic cleaners increase temperature even when not equipped with a heater. (Some industrial units are specifically certified as explosion proof.) When the unit is running, contact with the cleaning solution could cause thermal or chemical injury; the ultrasonic action is relatively benign to living tissue but can cause discomfort and skin irritation. Ultrasonic cleaners are electrically powered, meaning there is a risk of electric shock in case of malfunction, especially if cleaning solution comes into contact with electrified components. See also Parts cleaning Acoustic cleaning Washing machine Autoclave Macrosonics Sonication Tumble finishing Vibratory finishing References Ultrasound Cleaning methods