In all Manufacturing Districts, the density of emission of smoke during normal operations shall not exceed Standard Smoke Chart number 2, and the quantity of smoke shall not exceed a maximum of 10 smoke units per hour per stack in M1 Districts, 20 such units in M2 Districts, and 30 such units in M3 Districts. The method of measurement, additional limitations on the emission of smoke of a density not exceeding Standard Smoke Chart number 2, and the maximum permitted density and quantity of smoke during special operations such as building new fires, banking, or cleaning fires, soot blowing, or process purging, shall be determined in accordance with rules and regulations adopted by the Department of Environmental Protection.