chipster once bubbled...
Wow talk about conflicting responses...
with regards to having in analyzed, not always possible if you have a nitrox fill from the LDS than go somewhere where they do not have nitrox. Must to a calculation derived from the amount of top up of air in the tank for dive #2.
As has been said, getting accurate readings, and having the fill station at a similar temperature to your tank is important. You will get an *approximation* of the mix in the tank this way. That being said, the advice of dive the most conservative MOD and most conservative N2 loading is very sage.
chipster once bubbled...
I would tend to agree with mine and others here that rounding up would be more cautious then rounding down. Would think that if I rounded down might accidently exceed MOD. Also I have some wiggle room for % of obsorbing N2 as I have my computer set at 1.5ATA not 1.6. Needless to say it sounds here, that one should be cautious with there MOD If rounding up, and on the flip side dont push the max BT if rounding down.
Sound about right???????:doctor: [/B]
You got it exactly backwards.
a. You can do the MOD calculation in your head/calculator/dive computer before you get in the water, and monitor it easily using your brain. Your intended depth should not approach your MOD. If you are waiting until you hear the computer beep at you to stop descending then you have a problem.
b. You cannot easily do the N2 loading in your head (GUE folks excepted), and that's where the computer can help you. However if you want the N2 loading to be conservative then you should round *down*, not up.
c. How does setting your computer to generate an alarm at 1.5 ppO2 give you wiggle room for N2 loading? I assume this is just a thinko? (like a typo..)
The only dissenting opinions are from your original post and ChrisPete's. There isn't a plethora of different conflicting answers on this.
That being said, you can probably get away with rounding either way without difficulty. Deco theory is a blunt tool. If you round up then you are intentionally erroring away from caution.
If you are using an inexpensive pressure gauge and doing air tops on a boat (or whatever) without an analyzer then you have a very real chance of exceeding your MOD, especially if you are intentionally diving to 1.5 on a mix that you unsure of.
If you'd like an inexpensive analyzer, take a look here. I believe the kit analyzer runs about $100.
http://oxycheq.com/
Of course Big-T's advice is perfectly fine as well (know that you will not exceed the MOD of the richest gas).
Best of luck, and safe diving.