Using 100% oxygen for offgasing

[mwenner]

Go up to IANTD's website and look through all the deco tables, and you'll see the advantages (less time spent in the water off gasing) of using 75%> O2. As soon as you own a bottle of the stuff, and start cleaning your regulator's and the bottles for O2 use you'll find out about the tip of the iceberg of information that you need to know.
IANTD or TDS (to name a few) have comprehensive Tech. courses to certify you for concentrated O2 use, and I'd highly recommend getting your information there. IANTD's Technical Diver Encyclopedia is a wealth of info in case you're considering the long journey in pursuit of this level of diving.