1 1 gram of SO 2 for every million mL of air (parts per million by mass per volume). 2  Write ppm in terms of cubic meters. 3  There are a million cubic centimeters in a cubic meter (1 cm 3 = (10 -2) 3 m 3 = 10 -6 m 3) so one part per million of SO 2 by volume in air is actually 1 cm 3 SO 2 / 1 m 3 of air. 1 gram of SO 2 for every million grams of air (parts per million by mass); 2  1 mL of SO 2 for every million mL of air (parts per million by volume); 3  1 gram of SO 2 for every million mL of air (parts per million by mass per volume). 4  Write ppm in terms of cubic meters.
Mining is classified by the method needed to reach the coal seam. When the coal is found close to the Earth's crust and taking away the overlying layers of material is not too expensive, surface mining is used to remove the top layers of materials and expose the coal.If coal is found in layers far from the surface, underground mining is the preferred technique.Vertical or slanted holes (shafts) are cut down to the mining area underground for ventilation for the workers and for transporting the miners, equipment, and coal.ining is classified by the method needed to reach the coal seam. When the coal is found close to the Earth's crust and taking away the overlying layers of material is not too expensive, surface mining is used to remove the top layers of materials and expose the coal.
This type of coal contains 20-30% moisture and can be used for heating or generating electricity.- Bituminous coal. A soft, dense and black coal. Bituminous coal is the most common coal and has a moisture content of less than 20%. This type of coal is usually used for generating electricity and heating in the home. - Anthracite coal. Also known as hard coal, this type of coal is hard and black. Anthracite is high in carbon and low in sulphur, with a moisture content of less than 15%. Anthracite is a naturally occurring smokeless fuel and is used in solid fuel cookers and boilers.