How do I clean the ultrasonic membrane when the clean indicator light turns red?

Unplug the unit first, then remove the tank cover and water tank. Pour out remaining water, fill with 13oz/385mL of water and swish it around, then pour it out. Clean the transducer/ultrasonic membrane with a 50/50 mix of white vinegar and water on a cotton swab, then wipe with a damp cotton swab. Never touch the membrane with your fingers or submerge the base in water.