released by trinitrotoluene (TNT) ranged from 900 to 1100 calories per gram. In order to standardise the use of the term TNT as a unit of energy, an arbitrary value was assigned based on 1,000 calories () per gram. Thus there is no longer a direct connection to the chemical TNT itself. It is now merely a unit of energy that happens to be expressed using words normally associated with mass (e.g., kilogram, tonne, pound). The definition applies for both spellings: ton of TNT and tonne of TNT. Measurements in tons of TNT have been used primarily to express nuclear weapon yields, though they have also been used since in seismology as well. Tonne of oil equivalent A tonne of oil equivalent (toe), sometimes ton of oil equivalent, is a conventional value, based on the amount of energy released by burning one tonne of crude oil. The unit is used, for example, by the International Energy Agency (IEA), for the reported world energy consumption as TPES in millions of toe (Mtoe). Other sources convert 1 toe into 1.28 tonne of coal equivalent (tce). 1 toe is also standardized as 7.33 barrel of oil equivalent (boe). Tonne of coal equivalent A tonne of coal equivalent (tce), sometimes ton of coal equivalent, is a conventional value, based on the amount of energy released by burning one tonne of coal. Plural name is tonnes of coal equivalent. Per the World Coal Association: 1 tonne of coal equivalent (tce) corresponds to 0.697 tonne of oil equivalent (toe) Per the International Energy Agency 1 tonne of coal equivalent (tce) corresponds to 0.700 tonne of oil equivalent (toe) Refrigeration The unit ton is used in refrigeration and air conditioning to measure the rate of heat absorption. Prior to the introduction of mechanical refrigeration, cooling was accomplished by delivering ice. Installing one ton of mechanical refrigeration capacity replaced the daily delivery of one ton of ice. In North America, a standard ton of refrigeration is . "The heat absorption per day is approximately the heat of fusion of 1 ton of ice at ." This is approximately the power required to melt one short ton () of ice at in 24 hours, thus representing the delivery of of ice per day. A less common usage is the power required to cool 1 long ton ( = ) of water by every 10 minutes = . The refrigeration