Oxygen Bars

During my brother's layover at Narita on his way here, he was able to try the oxygen bar. It was just something he wanted to try for the sake of experience. I think these were portable oxygen concentrators flavored with different scents. My brother did not feel any difference though, except for the smell. I imagined that inhaling pure oxygen would invigorate his bodily systems. Except that is did not.
I have heard of similar oxygen bars cropping up in different places. I suppose that this would be popular in urban areas. I read that one of the benefits is supposedly to relax you. In theory, it sounds plausible. Maybe the relaxing benefits of going to an oxygen bar would be felt more radically if one were coming from a stressful period, much like how a massage feels particularly good after a stressful time.