On second thought, I think maybe I'll leave the interesting stuff alone. I'm scared of worms. It's better discussed in person, over a beer.
As for the diver vs vessel engaged in commercial diving operations point, it's a close one. Although OSHA doesn't have the authority to enforce it, they do require that the Alpha flag be displayed during commercial diving operations via the Coast Guard regs. One could argue that since the coast guard regs exempts instruction from the regulation, that there is no requirement, for yhe alpha flag, but It is my contention that if you want to be nit picky technically correct, the requirement still exists in the OSHA regs, enforceable or not, that the Alpha flag must be displayed if the instructor/guide is breathing nitrox, and that this would identify the vessel as being engaged in commercial diving operations (The flag itself doesn't necessarily denote commercial per se, but the regulations do make a distinction between the red and white recreational flag and the Alpha flag, and specifically require the Alpha flag in the case of commercial diving).
OSHA requires that the alpha flag be flown during commercial diving operations, but has no authority to cite for not flying it. From the OSHA Commercial Diving Instruction June 13, 2011
The requirement for displaying the warning signal when the dive location is located on a vessel is covered by the U.S. Coast Guard Inland Navigation Rules. These requirements are not enforceable by OSHA. If the CSHO observes violations of the warning signal when the dive location is on a vessel, no citation shall be issued. However, the CSHO shall inform the employer of the violation(s) and recommend abatement(s). The CSHO also shall note the incident on the OSHA-1 Form and notify the nearest U.S. Coast Guard Office of the violation(s) (see http://homeport.uscg.mil or USCG Phonebook
I know that in reality, at least for the time being that this stuff really doesn't matter. I understand that this whole discussion is a discussion of minute technicality piled upon minute technicality. The fact of the matter is that I just love this kind of weird ****, and as a great man once told me, "It only matters if accuracy is important
If anyone wants to go near the worms, understand that the alternative conditions final rule excepts employers of instructors/guides from the
chamber requirements of the commercial diving standards only, and that the rest of the standard still applies. This can be found here:
http://www.osha.gov/OshDoc/Directive_pdf/CPL_02-00-151.pdf and makes for some terrifying reading.
It makes, at the very least, a pretty good case for contracting dive guides and instructors. Also, oddly enough, if instructors/guides are on air none of the standard applies.
Thanks for the interesting discussion.