The answer to 'when to service humidifier' is that you should service your humidifier at least once per year, or more frequently if you notice any issues. Proper maintenance is important to ensure your humidifier is working efficiently and effectively.
You'll want to clean the humidifier's water tank, filters, and other components to remove any buildup of minerals or bacteria. This helps prevent the growth of mold and mildew, which can be harmful to your health. Following the manufacturer's recommended maintenance schedule is the best way to keep your humidifier in top shape.