CHAPTER 7 — Scuba Air Diving Operations Change A 7-5 7-2.2.2.1 Sizes of Approved Scuba Cylinders.  Approved  scuba  cylinders  are  available  in several sizes and one or two cylinders may be worn to provide the required quan- tity of air for the dive. The volume of a cylinder, expressed in actual cubic feet or cubic  inches,  is  a  measurement  of  the  internal  volume  of  the  cylinder.  The capacity of a cylinder, expressed in standard cubic feet or liters, is the amount of gas (measured at surface conditions) that the cylinder holds when charged to its rated pressure. Table 7-1 lists the sizes of some standard scuba cylinders. Refer to the NAVSEA/00C ANU list for a list of approved scuba cylinders. Figure 7-3.  Typical Gas Cylinder Identification Markings.   Table 7-1.  Sample Scuba Cylinder Data. Open-Circuit Cylinder Description (Note 1) Rated Working Pressure (PSIG) Floodable Volume (Cu.Ft.) Absolute Air Capacity at Rated Pressure (Cu.Ft.) Reserve Pressure Steel 72 2,250 0.420 64.7 500 Steel 100 3,500 0.445 106.4 500 Steel 120 3,500 0.526 125.7 500 Aluminum 50 3,000 0.281 48.5 500 Aluminum 63 3,000 0.319 65.5 500 Aluminum 80 3,000 0.399 81.85 500 Aluminum 100 3,300 0.470 105.9 500 Note 1:   Fifty cubic feet is the minimum size scuba cylinder authorized. SEAL teams are au- thorized smaller cylinders for special operations. DOT3AA2250 Z45015 PST AB 7-90 + 1.  DOT material specification, DOT3AA service working pressure 2,250 PSIG. 2.  Serial number assigned by manufacturer, Z45015. 3.  Identification mark of manufacturer or owner, PST. 4.  Inspector’s stamp, AB. 5.  Month and year of qualification test, 7-90. 6.  Plus sign (+) indicates air allowable 10% over service pressure. DOTSP6498/3000 OR DOT3AL/3000 Z45015 AB 7-90 1.  DOT material specification, DOTSP6498 or DOT3AL service working pressure 3,000 PSIG. 2.  Serial number assigned by manufacturer, Z45015. 3.  Inspector’s stamp, AB. 4.  Month and year of initial qualification test, 7-90. STEEL CYLINDERS ALUMINUM CYLINDERS