  Crushed stone, for example, has a density of 100 pounds per cubic foot (lb/ft3), which is 1600 kilograms per cubic meter (kg/m3), which is 1.6 metric tons per cubic meter. Packed earth is about 95 lb/ft3, or 1520 kg/m3.
Harvard Business Review. Harvard Business Review. The Harvard Business Review (HBR) is a general management magazine published by Harvard Business Publishing, a wholly owned subsidiary of Harvard University. It is published 6 times a year and is headquartered in Brighton, Massachusetts.
Sour gas. Sour gas is natural gas or any other gas containing significant amounts of hydrogen sulfide (H2S). Natural gas is usually considered sour if there are more than 5.7 milligrams of H2S per cubic meter of natural gas, which is equivalent to approximately 4 ppm by volume under standard temperature and pressure. However, this threshold varies by country, state, or even agency or application.