During winter months when indoor heating can drive the humidity in your home down to 20 percent or less, an animal-shaped ultrasonic humidifier can go into overtime replacing moisture in the air in a child's room. If an ultrasonic humidifier breaks down, check for a blocked vibrating membrane, which is at the heart of every ultrasonic humidifier. Before tossing the humidifier, attempt a basic repair at home.
Learn how the humidifier works. The ultrasonic humidifier uses a membrane to create pressure waves in the water that are gradually released into the air. The pressure waves are strong enough that when they reach the surface of the water above the vibrating membrane they "kick out" individual surface molecules of water, creating the water vapor.
Examine the humidifier. Make sure the control light shines green, the water tank is full, and the reservoir below the main water tank is full. If everything is in order, but there is no water vapor or very little vapor, the membrane may be blocked by lime scales, minerals or a drowned insect.
Remove the main water tank. Don't touch anything inside, but turn the humidifier on. If you see little drops jumping out of the water and fog created above the water surface, the membrane and humidifier are OK and something is blocking the outlets for the vapor. Check the main water tank for obstructions.
Unplug the humidifier and look into the inside tank to identify the membrane, which may look different depending on the humidifier. Look for a round rubber plate in a circular frame. Examine the membrane and the sides of the tank for particulates from the water and lime scale. If the membrane collects enough debris, it cannot generate a pressure wave strong enough to create a vapor.
Clean the inner water tank to get all the particulates out of the membrane and the space between the membrane and the frame. Wash it out with a stream of water from the tap or water hose, avoiding the electrical parts inside the box. Put the parts of the freshly cleaned humidifier together and turn it on.