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Sure. And that is another viable option but not for the novice or vacation diver unless you've got money to burn. I can see it now. "Honey, you know that expensive boat cruise with the dinner we were going to take, and that day of guided sightseeing? Well, we can't do it because I have to buy a...

Right, but my point was what instructors are doing. There are some instructors here on SB that still teach tables. Now, whether the students actually use them is a different matter. I still carry tables in my dive log book as an option. If my computer fails and I cannot rent one my preferred...

And for too many people the cell phone is their substitute brain. Back in 2011 when I got re-certified as OW I was taught tables. I didn't have any trouble understanding and using tables and even used them for a year before I bought my first dive computer. Looking back I can appreciate the...

I would highly recommend "The Complete Diver" by Alex Brylske. It's an everything you want to know about diving book.

I haven't read all 38 pages so maybe this has been addressed earlier. If you don't need to look under the water why not inflate your BCD/wing so that you ride higher above the water?

During your OW/AOW course your instructor (should have) taught you to check your gas remaining and NDL time remaining frequently especially as you go deeper. A very low NDL is not a concern for panic. For example let's say you get distracted and check your gas and NDL. Gas remaining is good but...

No stop limit (NSL) and no decompression limit (NDL) are the same. I prefer NSL as that term conveys the idea more accurately. In the calculation of NDL there are no assumptions, estimates or guesses. The calculation is based on the amount of inert gas the CTC (controlling tissue compartment)...

I think you're confusing GF with GF99. As Dmaziuk has already pointed out GF increases from GFLo to GFHi. It never decreases. You keep saying total ambient pressure. The total ambient pressure in the inspired gas includes both N2 (and possibly He) and O2. O2 does not contribute to DCS. It is...

What do you mean by "your chosen GF"? GF99 is calculated the same way that GFLo and GFHi are using the inert gas pressures. If we determine the first stop according to GFLo and follow a continuous ascent to the surface arriving at GFHi, the computer would need to calculate a current GF based on...

The more I think about it there would be a step change because the inert gas at ambient pressure is changing instantly at the switch from 52.14 to 0 fsw.

No. It won't be a step change because the new value of inert gas in the tissues is not just defined by the difference but by the half-time of the controlling tissue compartment according to Schreiner's equation.

Actually, it would be the opposite. GF99 would increase because the rate of off gassing would increase. For example: breath air (21% O2 + 79% N2) at 33 ft of sea water until the tissues are saturated, then switch to 100% O2. Let's neglect the MOD of the O2 for arguments sake. The total pressure...

Nope. You are badly mistaken. On and off gassing have to do with the inert gas pressure only. You even say so in your post above by your use of the term "partial". Flow of nitrogen in and out of the tissues is driven by the inert partial pressure of that gas. The quote below is from the...

This can't be right. The GF99 is the % value between ambient pressure (which is 0%) and the m-value at that depth (100%) for the controlling tissue compartment (CTC). Off gassing can only occur when the CTC pressure is above the ambient pressure which is the inspired gas pressure. Since GF99 of...

...and there are more factors: is this a repetitive dive (2nd, 3rd, 4th dive)? Was there a short surface interval? Is the dive deeper? Higher computer conservatism will have you going into deco sooner.

Thanks. It took me at least five years to get it close to what it is now, and I credit a few key people for helping me along the way. I have been working on a newer version to calculate a continuous ascent to the surface for deco dives. Unfortunately, because of all the additions in new features...

Yes. The spreadsheet is designed to mimic dive decompression software. It is designed as an educational tool with no safety warnings. It also does calculations for ppO2, NDL, ceiling, END, EAD, density, ICD, and gas usage. It supports up to five dive profiles which can be linked together to...

Using my example from above of GF = 60/80 and the first stop at 40 ft I get a slope of: slope = (80 - 60) / (0 - 40) = -0.5 GFcurrent = -0.5 * 40 + 80 = -20 + 80 = 60 ;first stop = 40 ft GFcurrent = -0.5 * 30 + 80 = -15 + 80 = 65 ;next stop at 30 ft GFcurrent = -0.5 * 20 + 80 = -10 + 80...

After re-reading the above post I realized the Schreiner I cited above might be confusing. I copied it from my code in the spreadsheet and the function name in VBA for e raised to some power is EXP. Let me rewrite the equation to make it clearer: p = Pi + rate * (t - 1 /k) - (Pi - Po- rate / k)...

Thanks JMarc. My post above is corrected.