The dusters have a sq. footage rating for each model you can check. They work well in a specific area to recirc the air and reduce smell, but if you have solvent printers or prints in the area, you will be replacing the cleaned air with new smelly air, so well it makes a difference, it does not eliminate smell all together. A "source air capture" system that mounts directly on a machine seems to do more for eliminating odors, but does nothing for the odors off of prints sitting in your shop outgassing. Island air sells both, PAT Technologies sells the source capture only.
The best of both worlds? A source capture at the printer and a smaller island air around you work table/print finishing area.
In a nutshell, they do make a difference. As many people have switched to ecosolvent or Latex inks, they are often available used as well.
Remember to switch your charcoal out occasionally.
Craig