How do the red and blue indicator lights in my Philips Humidifier work?

When the desired humidity level is reached, the colour of the humidity indicator light is blue. When the humidity level is not reached, the colour of the humidity indicator light turns to red.

There is a float (a floating ball) inside your Philips Humidifier's tank. When the water level gets low, the float activates a water level switch and this will activate the red indicator light.

Note: sometimes, this floating ball can get stuck and fail to activate the water level switch. When this happens, your humidifier will not display a low water indicator. You can solve this by moving this ball with your hand.