are typically sold as small screw-on accessories that fit inline with the hoses used to connect an RV to the water supply, which are almost always screw-thread-compatible with the common garden hose. Breathing gas supply Pressure regulators are used with Diving cylinders for Scuba diving. The tank may contain pressures in excess of , which could cause a fatal barotrauma injury to a person breathing it directly. A demand controlled regulator provides a flow of breathing gas at the ambient pressure (which varies by depth in the water). Pressure reducing regulators are also use to supply breathing gas to surface-supplied divers, and people who use self-contained breathing apparatus for rescue and hazmat work on land. Supplementary oxygen for high altitude flight in unpressurised aircraft and medical gases are also dispensed through pressure reducing regulators from high-pressure storage. Mining Industry As the pressure builds rapidly in relation to depth, underground mining operations require a fairly complex water system with pressure reducing valves. These devices must be installed at a certain distance interval, usually . Without such valves, pipes would easily burst and pressure would be too great for equipment operation. Natural Gas Industry Pressure regulators are used extensively within the natural gas industry. Natural gas is compressed to high pressures in order to be distributed throughout the country through large transmission pipelines. The transmission pressure can be over and must be reduced through various stages to a usable pressure for industrial, commercial, and residential applications. There are three main pressure reduction locations in this distribution system. The first reduction is located at the city gate, whereas the transmission pressure is dropped to a distribution pressure to feed throughout the city. This is also the location where the odorless natural gas is odorized with mercaptan. The distribution pressure is further reduced at a district regulator station, located at various points in the city, to below 60 psig. The final cut would occur at the end users location. Generally, the end user reduction is taken to low pressures ranging from 0.25 psig to 5 psig. Some industrial applications can require a higher pressure. Back-pressure regulators Maintain upstream pressure control in analytical or process systems Protect sensitive equipment from overpressure damage Reduce the pressure difference over a component which is not tolerant of large pressure differences. Gas sales lines Production vessels (e.g., Separators, heater treaters or free water knockouts) Vent or flare lines Hyperbaric