Heavily soiled areas require the application of manual spotting, pretreatments, preconditioners, and/or "traffic-lane cleaners", (commonly sprayed onto carpet prior to the primary use of the dry-cleaning system) which are detergents or emulsifiers which break the binding of different soils to carpet fibers over a short period of time. For example, one chemical may dissolve the greasy films that bind soils to the carpet, and thus prevent effective soil removal through vacuuming. The solution may add a solvent like d-limonene, petroleum byproducts, glycol ethers, or butyl agents. The amount of time the pretreatment dwells in the carpet should be less than 15 minutes, due to the thorough carpet brushing common to these "very low moisture" systems, which provides added agitation to ensure the pretreatment works fully through the carpet. The benefit of dry carpet cleaning, over wet solutions, is that dry chemical compounds do not attract dirt, like dried shampoo. While dry carpet cleaning is more expensive and more time consuming to clean than bonnet or extraction, dry cleaning formulas put less stress on the carpets themselves.