No person shall operate upon any street or alley or highway, any motor vehicle in such manner as to permit escape therefrom any unnecessary smoke, gas, steam, or offensive odor, or in such manner as to discharge any embers, oils, or residue from the fuel used in the operation thereof. Proof of the escape from the motor vehicle of any steam, smoke, gas, or offensive odors shall be prima facie evidence that the same is necessary.
(1972 Code, § 5-307) Penalty, see § 70.99