The Emblaser is designed to supply a positive air pressure within the laser guard in an effort to force fumes away from the lens and cutting region.
Sometimes these fumes contain particles that a charged and attracted to the inside surface of the laser guard. Over time there may be a noticeable buildup.
If you do notice a buildup, simply remove the laser guard and rinse it under some warm water. This should remove the buildup. Fully dry the laser guard before reattaching it to the laser unit.