American Standard Safety System
The American Standard Safety System, or ASSS, is a connection system for gas cylinders with a volume exceeding 25 cubic feet. The connections differ in thread type and size, right and left handed threading, internal and external threading, and nipple-seat design. This variability reduces the risk of errors such as administering the wrong gas to a patient, or utilizing equipment calibrated for one gas with another. However, as there are only 26 connections for the 62 gases and mixtures recognized by the CGA, connections are not unique.[1]
Connection specifications will be listed in cylinder catalogs as a list of abbreviations and numbers, such as that for O2, CGA-540 0.903-14NGO-RH-Ext. This means that the Compressed Gas Association has classified this connection as number 540, the thread bore is 0.903 inches, with 14 threads per inch. The connection is right-handed (RH) and must be turned clock-wise to tighten. The threading is external, so the connections of the cylinder and the attached equipment must be fixed together using a nipple, which is signified by NGO. A nipple is a bolt which fits together two male connections. Internal (Int) threading allows for equipment to be screwed directly onto the cylinder outlet.[2]
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