Alert Diver, the DAN magazine, recently published an article by Dan Orr Your Gas Supply.  While I agree with many of the points made,  I think there is a simpler and safer way.  It is a procedure we teach in our YMCA class called The Rule of Thirds that I wrote about in a February article in Scubaology.com.

Dan’s article has five (5) major points;

• Estimate - estimate how much air you need for your dive
• Check It - check your equipment
• Monitor It - watch both your and your buddys gas supply
• Call It - at what pressure do you and/or your buddy terminate the dive
• Plan It - this part of the article talks about “Rule of Thirds”

If you start with the “Rule of Thirds” you should always have enough gas to do your safety stop and return to a boat with at least 500 PSI, unless their is an equipment failure or you are lost. 

Full disclosure, I am a member of DAN and supporter.  In our YScuba classes we encourage all our students to join DAN.  I believe DAN is a great organization and has helped save many lives with their medical response team and other services.  I hope you will support DAN too!