The Disaster Response Unit is a unit of highly trained firefighters, demolitionists, engineers and rescue workers under the command of the Department of Energy. Their primary mission is to respond to a number of environmental man-made disasters involving energetics and dangerous chemicals. They operate on a "call" system, denominating the type of disaster which they are responding to.
- GREEN-CALL refers to emergencies involving large quantities of toxic chemicals, usually their spillage, but sometimes also their combustion.
- YELLOW-CALL refers to emergencies involving the spillage or leaking or large quantities of petroleum or natural gas, but which have not yet combusted.
- RED-CALL refers to emergencies involving the large-scale combustion of hydrocarbons such as petroleum or gas, which by their nature are extremely hard to extinguish.
- GREY-CALL refers to emergencies involving mine explosions, usually arising from pockets of methane or the proliferation of coal dust.
- VIOLET-CALL refers to emergencies involving radiological hazards, characterised by the fact no nuclear reactions have taken place, such as leaking medical equipment.
- BLACK-CALL refers to nuclear emergency incidents, of which there are two types; the dreaded nuclear meltdown and the far more destructive atomic bombing.