Carbon dioxide systems are of two general types, high pressure and low pressure. In high pressure systems, carbon dioxide is stored at room temperature in cylinders; in low pressure systems, at 0°F (-18°C) in refrigerated tanks. Carbon dioxide discharge falls into two broad categories, total flooding and local application. Total flooding systems are intended to protect enclosed special hazards such as rooms or spaces involving flammable liquids or containing electrical equipment, records, furs, or other storage where a fire would be extinguished by inert gas. Local application systems are intended to protect flammable liquids in unenclosed special hazards such as dip tanks and drain boards by discharging carbon dioxide directly on the burning material. When liquid carbon dioxide under pressure is released to the atmosphere through a nozzle, it changes into the solid and gaseous states, producing a white cloud of dry ice particles and condensed water vapor from entrained air. The dangers of carbon dioxide in fire-extinguishing concentrations are those of suffocation and of reduced visibility to persons exposed. When total flooding systems are used, a predischarge alarm and time delay should be provided to permit evacuation of personnel before the actual discharge. When local application systems are used, the gas is not confined and there is little hazard, except in low spaces where the gas may collect. System design depends on many factors, including the nature of the hazard and the characteristics of the equipment used in the carbon dioxide system.