The emission, from all sources within a commercial or manufacturing zoning lot, of particulate matter containing more than 5% by weight or particles having a particle diameter larger than 44 microns is prohibited. The rate of emission of particulate matter from all sources within the boundaries of any lot shall not exceed a net figure of 1/2 pound per acre of lot size during any one hour. Dust and other types of air pollution borne by the wind from such sources as storage areas, yards and roads within the boundaries of any lot shall be kept to a minimum by appropriate landscaping, paving, oiling, wetting or other acceptable means. The emission of smoke or particulate matter of a density greater than No. 1 on the Ringelmann Chart as published by the U.S. Bureau of Mines is prohibited, except that Ringelmann No. 2 or No. 3 will be permitted for five minutes during any eight-hour period for the purpose of building fires or soot blowing.