The number of semester credit hours required for an associate degree depends on the college and degree program. In general, an associate degree takes two years full time and represents half the work required for a bachelor's degree.
A dekatherm (dth) is a unit of energy used primarily to measure natural gas, developed in about 1972 by the Texas Eastern Transmission Corporation, a natural gas pipeline company. It is equal to 10 therms or 1,000,000 British thermal units (MMBtu).
Natural gas is a mixture of flammable gases, mainly the hydrocarbons methane and ethane, that occurs beneath the surface of the Earth. Helium is also found in relatively high concentrations in natural gas. Manufactured gas is derived principally from coal and petroleum.