These very tiny particles can be dust, pollen, mold spores, lint, cooking grease and oils, and animal hair.
Some particles are too small to be trapped by filters such as vacuum cleaner bags.
Hypothesize that a vacuum cleaner does not trap all of the particles that it sucks up. If this proves to be true, then people should vacuum their home before they dust the furniture, because will actually take some particles from the rug and throw them into the air. Either upright or a round canister type vacuum can be used. Take one strip off. Examine it to see if any particles of paper from the vacuum bag came off.