Kilns used for firing ceramic ware, heated exclusively by natural gas, liquid petroleum gas, electricity, or any combination thereof are permitted by rule where the conditions of this section are met:(1) the total heat input is ten million British thermal units per hour or less; and(2) there are no emissions of lead, beryllium, or fluorides, and emissions of sulfur dioxide and particulate matter from both the material being fired and fuel burned do not exceed 25 tons per year of either air contaminant.