Dave writes:

so one cannot by breathing oil-contaminated air at one atmosphere draw
any conclusions about the effect of breathing oil-contaminated air at
multiple atmospheres.

The irrelevance was the reference to "multiple atmospheres" and the
vacant definition of "oil contaminated".

It's great that the macho diver men know all about deep diving and air
purity. It doesn't earn you bragging rights for improvised hookah.

We po' boat do-it-yourself'ers are jus' tryin' to dunk under the surface
to work on the hull. The shop air and 1970s ScubaPro 2nd stage works
fine. Looks good, tastes good, smells good, breathes good. No residues
in the hoses or gear, no irritation felt, no respiratory effects noted
whatsoever. No measurable loss of oil in the crankcase after hours and
hours of runtime. Forgive my moral courage in scientifically evaluating
a system for PEL and risking my lungs on a measured negative conclusion.
The likelihood of being harmed by an error in judgment in this
enterprise is negligible compared to errors in driving down the road
this week.

Invisible-things-will-get-you is a habit of the uncritical or unbalanced
mind. I've looked in the closet, and there is no monster there. No
radon in the basement, no toxic mold in the walls, no dust mites in the
ducts, no subluxations in the spine, no bad humours in the shop air.