Replaceable paper vacuum bags do a better job of trapping the small particles which pas through cloth bags back into the room. High efficiency vacuum bags, also called microfiltration bags, are no available and trap even smaller microscopic particles such as mold and mildew spores and dust mite byproducts, often found to be a source of allergies. This type of bag is sold under several brand names. Verify that these bags trap particles smaller than two microns. All vacuum bags should be checked often and replaced when 1/2 to 2/3 full.