What is the most logical next event?

How to clean a humidifier filter
Unplug your humidifier.
Before you disassemble your humidifier unit, make sure it's turned off and disconnected from the wall outlet. You're going to be handling a lot of wet parts, so this will help you prevent any accidents or damage.
Choose a flat, water-resistant surface as your work area. A countertop near the sink is optimal.