There is dust on the laser and it needs to be cleaned.
The material that is cut out with laser engraving is removed from the larger material as dust and very small fragments. The material is disintegrated into dust that goes into the air or on the floor in small quantities.
diamond dust laser other diamond
You can take a normal laser pointer and point it at smoke, dust, fog, steam, etc. and the laser will appear. The normal old laser is now safe to "touch".
You can see light rays with dust, flour, etc. If you turn on a flashlight, you can drop dust right where the light travels to actually see that beam of light. The same thing happens with red laser beams.
you can, it all depends on the type of laser.
Diamond dust is formed, which is collected, saved and then employed as an abrasive.
toner
The reason we can only see lasers through dust or cloudy water is because our eye can only see light that enters directly into them. When a laser travels across our plane of vision the laser beam is traveling in a straight line, but when it hits the small particles of dust that light is being reflected in an infinite number of directions. A portion of those reflected light rays enter our eyes resulting in what appears to be a laser beam.
Toner is used in laser printers and photocopiers.
usually dust of some kind, occasionally water vapor, reflecting the laser light. I am assuming, of course, the part of the beam outside the excitation tube.
If there is dust in the air you can see it as it hits these particles. By the way, you can't see any form of light, laser or otherwise, as it passes through clean air.