Perchloroethylene/Trichloroethylene are the two special organochloro compounds. These products are often used for the dry cleaning solvents. Perchloroethylene is also known as Tetrachloroethylene (PCE or Perc), is a kind of sweet nonflammable colorless chemical with a stench that its odor threshold is 1 ppm. Trichloroethylene (TCE) is a volatile, nonflammable and colorless liquid. The product is widely used in industry as a solvent in dry-cleaning, as a degreasing agent for manufactured metal parts and as a precursor in the production of chlorofluorocarbons.