Warning-even if the vac has a clean air system-it is abuse to expect it to pick up hard items.Even though the stuff picked up won't go thru the fan-you can crack or break the floor nozzle housing-then you have an EXPENSIVE repair.I have seen many clean air vacuums waiting in vac shops waiting for repairs becuase someone tried it and broke the nozzle housing.The repairs were going to be at least half that of a new machine-I guess go ahead and do it to a machine you are going to junk.