"Bulk medical gas containers are a familiar sight at hospitals, large convalescent centers, and other health care facilities. Generally, oxygen and nitrogen are stored as cryogenic liquids, and nitrous oxide and carbon dioxide are stored as refrigerated liquids. Medical gases often are delivered to patient care rooms and surgery suites through a network of pipes supplied from the bulk storage tanks. Liquefied bulk storage often is the preferred method because of the volume of gases that are used on a regular basis."
Coffee Break Training - Fire Protection Series No. FP-2014-8
United States Fire Administration: http://www.usfa.fema.gov/