The liquid CO2 is stored in an ASME coded pressure vessel equipped with its own refrigeration system. The temperature within the vessel is kept at approximately 0 °F (-18 °C) by maintaining the internal pressure near 300 psi (20.7 bar). Valve control is electro-pneumatic or manual. Each master and selector valve assembly consists of either a ball or a butterfly valve, a spring-return pneumatic valve operator and a three-way electronically operated solenoid valve. Typical hazards protected by carbon dioxide systems include printing presses, transformer vaults/electrical cabinets, open pits, dip tanks, rolling mills, ovens, coating machines, process equipment, exhaust and fume handling systems, flammable gas or liquid storage areas, generators and inerting applications.