A method and apparatus is described for removing acid gases, air toxics and/or other contaminants from a flue gas stream formed during the combustion of fossil fuel, and/or waste materials. The flue gas stream is conditioned immediately downstream of the combustion source with a finely atomized liquid which is preferably water. The water spray decreases the volume of the flue gas and cools the flue gas to condense air toxics or heavy metals on the baghouse fabric filters. Advantageously, this may utilize the alkalinity inherent in the fly ash component of the particulate to assist in the removal of acid gases and/or other contaminants via adsorption. Also, the conditioned gas reduces the flue gas volumetric flow rate and hence the size of the particulate collection device, and the cost of the fabric filter media.