The examples below are NOT to be used to calculate decompression dives. Do not attempt to calculate the amount of gas needed to perform decompression dives solely on the Information within this text. Technical / decompression diving requires proper training.  Surface Consumption Rate, SCR. SCR is the average utilization of volume of  gas, air, over time. When you know your SCR, planned depth and time of a dive, you can get a good idea on the amount of gas you will need to support the dive.  Get a calculator, an 80cf aluminum cylinder filled with approx. 3000 psi of air, a water proof  timer, something waterproof to record your observations on. Find an area where 33 feet of seawater may be reached. A 35 foot deep area would work best to help guide you towards staying at 33 feet for ten minutes. Once … Read entire article »

Respiratory Mimute Volume, RMV, what is it for? In the post on Surface Consumption Rate, SCR you learned how much gas you would use and/or need to support a dive to a specific depth for a specific time. With RMV, you can now identify the volume of gas you would need to support a dive and perhaps the cylinder you could use to support the planned dive. Take the rate pressure of your scuba cylinder, again for this demonstration we will use an aluminum 80. An aluminum 80, or 80AL when filled to it’s working pressure, 3000 psi will hold 80 cf of gas. The working pressure of the scuba cylinder is stamped around the neck of the cylinder. Take the cubic feet of the cylinder and divide it by the working pressure of the tank. For an 80AL filled to 3000 … Read entire article »

Sunday, December 6th, 2009. Conclude the Open Water training with the same students from Saturdyas visit to Ginnie Springs. Also one advanced student needing their Deep and Navigation to become AOW certified. Everyone did exceptional and passed all of their water skills. Blue Grotto was all ours by 1pm. Probably because it was cold outside, colder than Saturday, but getting in the water felt good when compared. The earlier crowds has silted up the place, but since I was performing a Navigation course, this helped make the course more challenging. My student is a Boy Scout, and I expected him to do well on his navigation. He did excellent, following his reciprocal back from various point to his starting point. … Read entire article »

This article addresses how to calculate your Pressure Group after athe 2nd or 3rd dive. I thought this subject would be a good one. As an Instructor, one ofthe most common problems I find individuals having is calculatingthe correct Pressure Group at the end of a second or third, etc. dive. In my blogs on RDP, I showed you a little on how to use an RDP. We will  now work through an exercise that will demonstrate how to correctlyidentify the pressure group you will be in at the end of your dive. Pull out the AIR RDP. The process is the same for any RDP. We will startthis subject at the end of your first dive. Table #3 Let us begin You just complete your first dive of the day and ended in a PressureGroup … Read entire article »

What I mean in my Title is mixing processes of two different types of diving sometimes do not blend well together. During my Open Water training and all training in between OW and Instructor, I have been taught to open the valve of the tank all the way, then approx. 1/4 turn back. During my Close Circuit Rebreather, CCR rebreather training, I was taught to open the valves, just until they are open and stop. The reason for this is in an emergency, if for example the Oxygen begins to freeflow into the loop, you must address ‘the problem’ and get back on the loop. One way to stop O2 from free flowing is to turn off the O2. If you are at 180 feet, you can see the danger of your O2’s PPO spiking UP. Anyway, if the O2 valve was turned ALL … Read entire article »

Understanding the color codes on the DSAT RDP as they relate to depth and time. Let’s pull out and dust off that RDP and begin on Table 1. Table 1, the No Decompression Limits and Group Designation Table contains a bit of information. You have Pressure Group Designation running up and down the left side (The A – Z characters), Depths (found across the top of table 1), Times (the numbers found in the blue/white boxes), grey and black boxes.  Let’s focus on the grey and black boxes. Flip the RDP so you are viewing the side with Table 3.  Locate the paragraph reading Safety Stops. Let me quote the section. “Safety Stops  – A safety stop for 3 minutes at 15ft is required any time the diver comes within 3 pressure groups of a no-decompression limit, and for any dive … Read entire article »