![]() ![]() If both sets of cylinders are filled to 3600 psi and we use 1200 psi as penetration that means we have 86.4 cf in the LP95s. The LP95s are the limiting cylinder because they are smaller. This time we have divers with LP95s and LP108s doing a dive together. So the diver in LP95s should not breathe any more than 1067 psi if the diver in LP85s breathes 1200 psi. Take the 76.8 cf and divide by the tank factor of 7.2 and multiply by 100 (76.8/7.2 x 100). What we need to do is find out how much pressure that equates to in the LP95s. With a penetration pressure of 1200 psi that gives 76.8 cf. However, if the diver in LP95s were to adjust his turn pressure to volume match with his buddy then this wouldn’t be an issue.īecause LP85s are the smaller of the cylinders they are the limiting factor. ![]() What are the chances of having a catastrophic gas loss at maximum penetration? Yes, they are pretty slim, but most divers will experience an increase in gas consumption rate when any kind of incident happens during the dive so even if the incident was sooner or later, the diver in LP85s would probably not have enough for his buddy. He is almost 10 cf short of the gas necessary to get back to the surface. The diver in LP85s has 2400 psi, or 153.6 cf available. So what’s the big deal? Let’s say both divers reach their turn pressure of 2400 psi at the same time and suddenly the diver using LP95s has a catastrophic gas loss and has to air share with his buddy during the exit. This means that 1200 psi of LP85s is 76.8 cubic feet (cf). Their starting pressures are 3600 psi each, so they plan on a turn pressure of 2400 psi. Two divers, one with LP85s and one with LP95s plan a cave dive together. Let’s look at an example of a dive team planning based on pressure alone. Simply planning gas management based on pressure isn’t enough. When you’re diving with someone who has different size cylinders than you, volume needs to be accounted for. Not everyone has the same size cylinders. Whenever you plan any kind of overhead dive, whether one with an actual overhead or a virtual overhead, your dive team needs to plan gas management according to volume. ![]() If this is new to you, then please read carefully because this is very important information and something you should institute in your own dive planning. If you’ve had any kind of cave or technical training hopefully this will be a review for you and maybe help clarify things. A topic I discuss with all of my cave diving and technical students is volume matching. ![]()
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