Starbuck_II
Explorer
I see it as this.If they generate light (and so outline someone in a pitch-black room with glowing traces), then when the creature turns invisible, the dust particles will also turn invisible, but the light they generate will not... and so there will still be a man-shaped cluster of glowing pinpricks of light, which will exactly pinpoint the creature's location, rendering the concealment of the invisibility ineffective.
-Hyp.