No. Propane is an approved, clean fuel listed in the 1990 Clean Air Act and the Energy Policy Act of 1992. Propane is one of the cleanest burning of all fossil fuels. Tests conducted by the U.S. Environmental Protection Agency show that propane-fueled vehicles produce 30 to 90 percent less carbon monoxide and about 50 percent fewer toxins and other smog-producing emissions than gasoline engines. Propane is also nontoxic, so it's not harmful to soil or water.