Abstract: Apparatus is provided for reducing contaminants in gases containing products of combustion. The apparatus is particularly advantageous for reducing airborne sulfur in smoke from burning coal. This enables more use of coal, including high sulfur coal, without the concomitant problem of acid rain. The apparatus includes a duct or stack forming a first passage for directing the gases away from the source of combustion. A second duct forms a second, horizontal passage through which the gases flow from the first passage. A spray head is located at an upper portion of the second passage to direct a spray of water across the passage and into contact with the gases. A drain is located in a lower portion of the second passage to collect the water and contaminants trapped therein from the gases. The water can be cleaned and reused. The apparatus can also be employed with an internal combustion engine to reduce contaminants in the exhaust gases.