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I think you make it too hard for yourself. You're from Rotterdam (according to your profile)? Join a local club, go wreck diving in North Sea, Scapa Flow, Red Sea, Arenzano, Croatia, ... Why not take Fundies and book a one-week tour on a tec-friendly boat in the Red Sea with twin tanks for a...

Recreational Trimix is not a prerequisite for ART according to IANTD standards; Deep Diver and EANx are. The instructor however may require more. My ART instructor for example wanted to see Essentials or similar, or OW SM class before ART. He said he had too many recently self-taught...

That's interesting. So you use GFhigh to determine NDL time, and start deco calculation with GFlow only after NDL time is over? That would cause some weird effect in a dive computer: just a second after NDL time is over, suddenly a long deco plan is displayed with many stops, starting at a...

I wouldn't be so sure that 100% is actually better than 80% for first aid. While elevated O2 supply is certainly highly recommended for DCS, hyperoxia also brings disadvantages such as brain vasoconstriction and reduced cardial output, that limits its positive effects. In life support after CPR...

The impact of 50% vs 100% (one deco stage) on the needed amount of back gas is also considerable. In your example with EAN50 you need 2709l back gas on the bottom and 487l during ascent to 21m plus 1300l EAN50. You also want to be able to bring an OOG buddy to 21m and hence have at least...

My DSMB has an inflator valve; but after one hour in freezing cold water my lips are numb and stiff, and I can't seal my lips around it anymore well enough to inflate the DSMB. I also don't like to disconnect/reconnect my (quite short) drysuit inflator hose. So I use the reg exhaust. My DSMB is...

It's not a big issue actually. The member with highest O2 content limits MOD. The decompression obligation is determined by the member with lowest O2 content. Differences in Helium content have little effect on the decompression. Say you have two divers, one on air, the other one on EAN32. No...

A line y=0.79*x (let's call it the saturation line for an air dive) could be helpful as it would (a) show the boundary between on-gassing and off-gassing regions and thereby help illustrate the conceptual difference between on-/off-gassing p(tis)-p(inspired) vs. DCS risk p(tis)-p(ambient), and...

One can draw a graph with any x- and y-axis as you like. But remember there's a model behind it with arithmetic calculations where GF has a clearly defined meaning and these formulas are used in every Bühlmann decompression software. The graphs are only illustration. Please read "Clearing up...

GF=0 is NOT saturation. At GF=0, tissue partial pressure equals ambient pressure and hence exceeds inspired inert gas partial pressure, and is already far in supersaturation region. Your quote above from the Diverite document could use some clarification ... "there is no supersaturation...

GF=0 does not equal saturation. Saturation means, tissue partial pressure equals inspired partial pressure. GF=0 means, tissue partial pressure equals ambient pressure, which is larger. For an air dive, let's say you descended to 30m and stayed there until a fast tissue saturated to...

The pressure gradient for off-gassing is between the tissue pressure and the inspired inert gas pressure, not between tissue pressure and ambient pressure. You can swim along the AP line (GF0) and decompress very well as long as your breathing gas has less than 100% nitrogen, which is a good...

That's right, the first stop should be at GF30. But plotting the GFlow color scale right at the first stop will make it hard to read. It's a challenge to make this plot correct and easy to understand.

I don't think that Ross developed the software that calculates the bubble model, but that he just put a graphical user interface on top of Erik Baker's VPM-B code, that was V-Planner. In his many comments on this forum I got the deep impression that Ross' expertise is only on the Windows user...

I beg to differ but it does make a difference, because the M-value line is not parallel to the ambient pressure line (b<1), particularly for the fast compartments that determine the first stop. In the plot above, the dotted orange line is probably close to a GF20/80 line, not GF30/80.

Correct for VPM, but in VVAL18 there is a different idea: In a supersaturated tissue, there's more gas than what can stay dissolved, and this extra gas forms bubbles. Only the dissolved gas in the tissue participates in diffusion, whereas the gas stored in bubbles does not, so that the diffusion...

At first, ambient pressure is not relevant for off-gassing in the models (Buehlmann, VPM); off-gassing rate is determined by the difference between inert gas partial pressure in the tissue vs inspired inert gas partial pressure. You might want to look into linear-exponential model (VVAL18) by...

can get a new FST XTX 100 + XTX40 DS4 for 500€ ($588 USD) here, and that price includes 19% VAT already. That's $495 USD before tax.

Consider that this regulator market is very regional and local availability of brands depends a lot on the sales channel, less on the product. Over here in Europe, Atomics is rare, Sherwood, Diverite, Zeagle, Hog and Deep6 practically unheard of; British Apeks popular but mostly for Tec divers...

Can you elaborate how you would set GF for these different types of dives? The Bühlmann model itself is already nonlinear and calculates exponential inert gas uptake and elimination. If you pick always the same (say GF30/80) for every dive, ascent profiles will depend on depth and bottom time in...