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 ten smoke units per hour per stack. The method of measurement as well as the actual measurement of smoke emissions, 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 the rules and regulations established by the Ohio and U.S. Environmental Protection Agencies.