metridium once bubbled...
I agreed with you up to that point. Above 40', what difference does it make if you're not doing a very long duration dive?
Obviously, it makes far less of a difference at that depth. However, even on those dives, I prefer Nitrox for the following reasons:
First, by always keeping Nitrox 32 in my tanks, I maintain the flexibility to do almost any of the recreational dives in my area. It doesn't matter if we decide to change our dive site due to weather conditions, crowding, or because the boat opened up, I can dive without needing to change my fills. This is particularly important if the altered dive site results in a deeper dive, since I would otherwise be stuck with air NDL's or deco times.
Second, most of my favorite dives are in the 70' - 130' range. I seldom dive from shore unless the boat gets cancelled. Thus, on a practical level, I seldom run into a case where I would want to skip the Nitrox.
Third, while it is certainly less critical at shallow depths, I prefer the decreased nitrogen loading that results from using Nitrox. I see no reason to nitrogen load if I don't need to do so.
Fourth, by always keeping Nitrox32 in my tanks unless I'm doing a more technical dive, I never need to mess around with "best mix" calculations. Moreover, there is no chance that I'll make a mistake and calculate the dive using Nitrox32 when I should have used air or vice versa.
Fifth, since my regular buddies only dive Nitrox, there is no chance that we'll end up on radically different schedules at the end of a dive. We know that, unless otherwise discussed, we are going to be on 32.
There is one more reason that doesn't apply generally, but that I like to take into account.
I'm an AI. Most of my shallow dives are with students. While assisting, I tend to do multiple ascents and descents as I work with different groups. I prefer the added safety factor when I end up doing 6 ascents and descents during a one hour dive.
