Airframe manufacturers or design agencies have created criteria to allow different aircraft models to qualify and in all cases there are stipulations for continued airworthiness. It does become the responsibility of each maintenance technician to learn the criteria for the equipment being maintained as routine maintenance may have a bearing on the safe operation of the aircraft in the tighter confines of RVSM airspace. This could be something as simple as verifying proper closing of a nose compartment to something as complex as running an integration check of circuit cards during certain maintenance operations. It does require a visual inspection of RVSM critical areas during a daily pre-flight.
Just think, all this effort over a simple gaseous mixture. Seems like life was a lot simpler when air was used exclusively for breathing. I guess if that were still the case today all of us would be involved in another line of work.