A method of cleaning stack gases comprising the steps of: (a) providing in a stack adapted to pass stack gases through a first catalytic flow-through bed of calcium zeolite comprising natural zeolite particles of a majority between 44 μm and 64 μm in size at a temperature above the dew point between 51.67 and 260°C (between 125 and 500 °F) and a pressure between 0.02 and 1.38 MPa (between 3 and 200 psi) adapted to reduce carbon oxides in the stack gases; (b) providing in the stack adapted to pass stack gases positioned adjacent the first catalytic flow-through bed, a second catalytic flow-through bed of a blend between 25 and 75% of sodium zeolite and calcium zeolite comprising natural sodium and calcium zeolite particles of a majority between 65 μm and 125 μm in size at a temperature above the dew point between 51.67 and 260°C (between 125 and 500 °F) and a pressure between 0.02 and 1.38 MPa (between 3 and 200 psi) adapted to reduce nitrogen oxides in the stack gases; (c) providing in the stack adapted to pass stack gases positioned adjacent the second catalytic flow-through bed, a third catalytic flow-through bed of calcium zeolite comprising natural zeolite particles of a majority between 78 μm and 204 μm in size at a temperature above the dew point between 51.67 and 260°C (between 125 and 500 °F) and a pressure between 0.02 and 1.38 MPa (between 3 and 200 psi) adapted to reduce sulfur oxides in the stack gases; and (d) passing stack gases selected from the group consisting of volatiles from combustion of coal or from combustion of natural gas or from a cement kiln sequential through the first catalytic bed, the second catalytic bed, and the third catalytic bed each collecting materials in the catalytic beds and providing gas exiting the third catalytic bed with at least 70% reduction in sulfur oxides, nitrogen oxides and carbon oxide. (a) providing in a stack adapted to pass stack gases through a first catalytic flow-through bed of calcium zeolite comprising natural zeolite particles of a majority between 44 μm and 64 μm in size at a temperature above the dew point between 51.67 and 260°C (between 125 and 500 °F) and a pressure between 0.02 and 1.38 MPa (between 3 and 200 psi) adapted to reduce carbon oxides in the stack gases; (b) providing in the stack adapted to pass stack gases positioned adjacent the first catalytic flow-through bed, a second catalytic flow-through bed of a blend between 25 and 75% of sodium zeolite and calcium zeolite comprising natural sodium and calcium zeolite particles of a majority between 65 μm and 125 μm in size at a temperature above the dew point between 51.67 and 260°C (between 125 and 500 °F) and a pressure between 0.02 and 1.38 MPa (between 3 and 200 psi) adapted to reduce nitrogen oxides in the stack gases; (c) providing in the stack adapted to pass stack gases positioned adjacent the second catalytic flow-through bed, a third catalytic flow-through bed of calcium zeolite comprising natural zeolite particles of a majority between 78 μm and 204 μm in size at a temperature above the dew point between 51.67 and 260°C (between 125 and 500 °F) and a pressure between 0.02 and 1.38 MPa (between 3 and 200 psi) adapted to reduce sulfur oxides in the stack gases; and (d) passing stack gases selected from the group consisting of volatiles from combustion of coal or from combustion of natural gas or from a cement kiln sequential through the first catalytic bed, the second catalytic bed, and the third catalytic bed each collecting materials in the catalytic beds and providing gas exiting the third catalytic bed with at least 70% reduction in sulfur oxides, nitrogen oxides and carbon oxide.