Need help reading subsurface dive chart (for cressi giotto)

[V Ng]

Hi,

What do the green and black lines at the bottom represent?

Similarly, how do I interpret the heat-map area (blue shaded) section at the bottom?

(Units: pressure: psi, depth: meter, temp: C )

Thanks,

[JB2Cool]

Black line is pN2, Green line is pO2 and if you ever dive with Helium you can have a maroon/burgundy line which is pHe.

For the heatmap, blue is where your tissues are on-gassing, green is where they are off-gassing nicely and if it starts getting yellow or red they are starting to off-gas a bit too quickly. That's how i'd explain it. I think the heatmap is made up out of 16 horizontal lines, the topmost is the fastest tissue and the bottommost is the slowest tissue.

A picture might explain it more, have a look at this.

Here you can see my bottom gas has helium, nitrogen and oxygen in it but when i ascend to my gas switch at 21m the helium drops to zero and the oxygen content increases (nitrogen stays largely unchanged). The heatmap shows me moving from blue up into the green area and just touching on yellow/orange. A tiny bit of orange is ok (in my eyes) but make sure there is not too much of it and I certainly want this cleared and gone back to green before surfacing (as you get a spike when surfacing).

Hope this helps

Jason

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[JB2Cool]

Here is another one with 3 gases, you see the pressure changes better on this one (and my deco is cleaner).

[V Ng]

That makes sense! Thank you for the detailed explanations!