Really interesting article... all the numbers are completely believable, but seem really high based on the conference room effects at 0.1% They even refer to a person without a helmet in still air as being at 2000ppm, which is comparable to the worst tested "school house" data.

I'd argue that if there is an effect here it isn't the O2 concentration since a 1% change in atmospheric pressure happens at about 275ft. That's a pretty small hill!

A 1000ppm change in 02 partial pressure happens in about 30C temperature change. Really, if this is a real effect it better be actually due to some effect of C02 concentration.

Is there a link for the Elsevier-disabled people?

SciHub has it

Unfortunately Unpaywall (tip: install the browser extension!) doesn't find any: https://unpaywall.org/10.1016/j.apergo.2005.01.018

So unless you're willing to go the illegal route through Sci-Hub, I'm afraid you're out of luck.