A local exhaust system consists of a hood to capture the contaminants, ducts to transport them to the outside, an exhaust fan to move the air, and sometimes air cleaners to remove particulates from the air. Particular types of hoods are used for particular operations. OSHA requires local exhaust ventilation for abrasive blasting, grinding, polishing and buffing, spray finishing, and open surface tanks (23 CFR 1910.94). Exhaust ventilation is essential when solvents are used in confined spaces even in moderate amounts. Local exhaust ventilation which capture solvent vapors at the source may be needed. Local exhaust ventilation is usually needed indoors when highly toxic solvents are used or when large amounts of less toxic solvent vapors are generated.