As I'm getting more confident in my style of diving and the set up of my rig, I am beginning to get that itch to go deeper on occasion. Since most of my diving is in slack dependent areas it's only an occasional jaunt i'm after in no or low current areas. The catch is that I have no desire to use Helium and it's not my intent to debate here about why that is. My training certification is to 140 FSW, 5 minutes of deco, but i'm now taking short dips to 150FSW/50MSW and getting more comfortable with the idea of racking up some more deco. I'm noticing some of the narcosis and post dive fatigue I used to get on OC after deeper dives, yet the call of HE is still not there and frankly I missed that relaxing mellow feeling I used to get. Going through Mod II to get certified to go deeper would be a natural move except I have no desire to use Helium. If there was an advanced MOD 1, for non-helium divers that want to go deeper, i'd take it. Since there is not, i'm wondering how deep folks go on air dilluent and if there are guidelines for deeper CCR diving on air diluent. Obviously, going much deeper would require staged hypoxic bail out, probably a good enough reason to get more training right there. I'm guessing i'm not the only one in this boat.

Anway, how deep are folks diving on air diluent and how deep do you think it's safe to go?
Do you have any training recommendations that would help me venture forth in a safe manner?

your input is much appreciated!