... , if the temperature on the high side, such as tail gas/fume/dust from metallurgical plant, carbon black plant, iron works ... (blast furnace gas), cement plant (tail gas from vertical kiln), petroleum fumes from mixing round the beton and asphaltum, coal fired boiler, etc, the ... there may contain some material such as sulfur in the gas/fume, the acid dew will exist. Aramid needle felt, besides ...