Which Scuba Tank has the MOST air in it? | High Pressure VS Low Pressure cylinders explained 🤿

Many scuba divers are confused as to the meaning of "High Pressure" tanks or "Low Pressure" tanks. A common misconception is that "High Pressure" tanks give you more air, when in fact the opposite is often the case. Divers want to know how much air is ACTUALLY in a tank, so they can better plan their dives, and know what the pressure readings mean in terms of volume. When we buy or rent scuba tanks, they will have two marking on them that explain their size: The Volume and the Service Pressure. The volume refers to how much air (or gas) is actually in the tank, when filled to its rated service pressure. So when filled to the given service pressure, it would have the volume of air stated if you were to let it all out. For example, an aluminum 80, when filled to 3000psi, would have 80 cu ft in it. If you were to open it up, connect it to a giant balloon, it would blow up a balloon that would displace 80 cu ft in our actual atmosphere (it would be the size of a small compact car!). So if that tank was half empty (or half full), at 1500 psi, it would have about 40 cu ft in it, instead of 80 when filled to 3000, and so on. So a "High Pressure" tank actually requires a higher pressure to reach its stated volume, and a "Low Pressure" tank would not require as much pressure to reach its given volume. A High Pressure (HP) 80 tank might require it to be filled all the way up to 3442 psi to achieve its volume of 80 cu ft. A Low Pressure (LP) 80 might requires anything from 2250-2650 psi to achieve its stated volume of 80. So the low pressure does not have to be filled as high to reach its advertised volume. One advantage to a High Pressure (HP) tank, is that it is smaller, and less cumbersome in places like trunks, closets, and above all, a dive boat. Here are a few manufacturers websites with exacts specs on their tanks: *Tanks are formally called CYLINDERS. Commercial Divers often refer to them as BOTTLES. I call them tanks for simplicity, and to avoid confusion with non-divers. Dive Gear Express: https://www.divegearexpress.com/library/product-tips/aluminum-cylinders-at-dive-gear-express Catalina Cylinders: https://www.catalinacylinders.com/markets/scuba/ Xs Scuba hosts the specs for Luxfer, Worthington, and Metal Impact cylinders. For an even deeper dive or to learn the fine details of cylinders, inspections, and ratings, I suggest PSI - PCI: https://www.psicylinders.us/index.php/about Big thank you to Kris Shannon and Mark Gresham for always being available as reliable sources. Kenny Dyal Sweetwater Scuba