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.
Coal is a combustible rock and along with oil and natural gas it is one of the three most important fossil fuels. Coal has a wide range of uses; the most important use is for the generation of electricity. Coal forms from the accumulation of plant debris, usually in a swamp environment.When plant debris dies and falls into the swamp the standing water of the swamp protects it from decay. Swamp waters are usually deficient in oxygen, which would react with the plant debris and cause it to decay.oal is also used as a power source for factories. There it is used to heat steam and the steam is used to drive mechanical devices. A few decades ago most coal was used for space heating. Some coal is still used that way but other fuels and coal-produced electricity are now used instead.