Yes, there can be to much compressed oxygen in a hyperbaric chamber. If I can't clear my ears and can't go up to higher pressures then that's the first sign the air is too concentrated.
Some people want to get more oxygen but the pressurized air on the lungs can make it harder to breath so for those seeking 1.5 ATA chambers it is something to consider.
Many people with gut issues buy chambers to build up their aerobic bacteria. Those who are trying to kill Aaerobic bacteria prefer to stay in for longer sessions as the bacteria making them feel bad can't live in an oxygenated environment. Bad bacteria cannot survive well in an oxygenate environment. Many people take medicine. Others use high doses of oxygen to break down the bacteria so it can die.
Note: Oxygen is good if not overdosing on it (not burning it). So many people don't know when to get just enough and when they are over dosing.
Just like an apple turning brown when cut in half. When the cluster size of the oxygen is concentrated, the apple turns brown quicker. See my video on the apple at 1.3 ATA vs 1.5 ATA and watch which one oxidizes quicker. It's not about just getting more concentration of oxygen. It's being able to use the oxygen and burn it. I avoid too much oxygen when it's not needed and I am not "burning" it.
Note: those that have cells with inflammation and toxins have space apart cells. This makes it much harder to get oxygenated. This is why I urge people to look into lymphatic exercise and heating their core up as part of their hyperbaric session. Sludge blood cannot carry oxygen well.