[newacct583]

Ozone is indeed acutely toxic. But no, plain O2 will attack pretty much anything (i.e. literally everything in your body can be "burned") with a reaction rate that depends on concentration. At a partial pressure of 0.2 bar, that's negligible, but it stops being so at some point.

It's a known thing in diving planning, here's a wikipedia article on it: https://en.wikipedia.org/wiki/Oxygen_toxicity

Now, I'm sure these chambers aren't at those pressures. But everything is likely linear, and the thing they're "curing" is literally what we currently consider to be the normal baseline! Even a very small effect will swamp whatever longevity benefits they're seeing are.