The answer to 'humidifier freezing up' is that a frozen humidifier is a common issue caused by low water flow, low humidity levels, or cold air blowing directly on the unit. Symptoms include visible ice buildup, reduced humidity output, and the unit shutting off. Solutions include adjusting the water flow, increasing the humidity setting, and ensuring proper airflow around the humidifier.
If the issue persists or you're unsure of the cause, it's best to call an HVAC technician to diagnose and repair the problem. Attempting DIY repairs on a frozen humidifier can potentially damage the unit or create safety issues, so it's generally recommended to have a professional service it.