FAQ What does the red indicator light on the water supply mean? The red indicator light on the water supply will come on when the water tank needs to be refilled.How does the dust monitor work? The dust monitor continuously monitors the air and changes color to indicate the purity of the air in the room.What does the blue indicator light on the Plasmacluster mean? The blue indicator light on the Plasmacluster indicates that the Plasmacluster is turned on.