It is often necessary for trained personnel to provide a variety of gases of medical quality in a medical facility. Examples of such gases include medical air, oxygen, nitrogen, nitrous oxide, and carbon dioxide. Systems are also often installed in medical facilities which provide vacuum or gas evacuation. Gas service may be provided through a system which delivers the gas throughout a facility or portions or zones thereof. A number of primary supply sources of gas are used to deliver gas through outlet ports positioned at locations within the medical facility. The delivery system for each type of gas commonly includes manifolds with appropriate shut-off valves and pressure gauges. The delivery system also commonly includes at least one pressure regulator, check valve, and piping supply lines connecting the elements of the system. The primary supply source for each gas may be located in a secure area in the interior of the medical facility. Alternatively a primary supply source may be located at the exterior of the facility for maintenance by outside vendors providing the various gases.
It is critically important that the correct gas at the proper pressure be supplied when required from a medical gas supply system. Great effort is taken to assure that the various gases supplied are clearly marked at all locations. The possibility for delivery of the wrong gas at an incorrect location should be minimized. The pressure of each gas delivered may also be appropriately monitored throughout the system.
There are occasions which may require a secondary gas source to be connected to the gas delivery system of a medical facility. These instances might involve an emergency, a need for maintenance, a requirement of inspection, certification testing or service. One method of connecting the secondary gas source involves connecting the secondary gas source to the system through a hose to a conduit in the facility which normally serves as an outlet. Such an arrangement, known as backfeeding in the industry, is unacceptable according to the National Fire Protection Association (NFPA), the regulatory agency responsible for medical gas piping standards. Such a connection, according to NFPA, puts the system and possibly users thereof at risk of injury or damage.
Gases delivered by medical gas systems are generally at relatively low pressures. Typical desired pressure levels are 50 psi for oxygen, nitrous oxide, carbon dioxide and medical air, 180 psi for nitrogen, and 15 in/Hg to 25 in/Hg for vacuum or gas evacuation. Bottled gases by comparison have considerably higher pressures, commonly about 2000 psi. If the wrong gas were delivered to the wrong supply line through backfeeding, incorrect pressure or flows in portions of the system may occur. Such incorrect pressures and flows may place equipment and personnel at risk.
The medical system for each gas type is designed to provide gas flow from the primary source toward the various outlets and devices which utilize the gas within the medical facility. Gas should not be allowed to flow in a direction opposite to that for which the equipment was designed. Reverse operation requires a user to thoroughly understand every component of the system and what is necessary to safely accomplish reverse flow. It is often difficult to conduct such an analysis when many types of devices may be connected to the system.
For these reasons NFPA has disapproved of the practice of backfeeding of gas supply lines. Despite the NFPA position, personnel in medical facilities when faced with the necessity of keeping gas systems in operation are forced to use such backfeeding connections. In 1996 NFPA took the position that emergency service of an oxygen supply could be provided by a low pressure inlet located in the main supply line. This inlet is required to be located at the exterior of the medical facility. The use of such an inlet is authorized only for use to achieve an emergency supply of oxygen and is not to be used in the case of inspection/certification. Since this emergency inlet port is not required to be retrofit into existing "grandfathered" systems, most medical facilities are not equipped with this capability. Such an arrangement is of no help when the problem in the system is something other than the main supply, such as a system break inside the medical facility. In addition, gas delivery systems are normally divided into zones. This port does not allow gas service to be selectively supported or inspection/certification activities to be performed by selected zones. As a result, even in oxygen systems which have such a port the practice of backfeeding is sometimes necessary.
Thus there exists a need for an apparatus and method for connecting a secondary supply of a medical gas to a medical gas supply system. There further exists a need for an apparatus and method of connecting such a secondary supply of medical gas in a quick and reliable manner, which can be connected to selected zones of the supply system and which does not require backfeeding of any portion of the gas supply system.