The 1 to 2 hour session is the most popular session time. Most people do a 2 hour session in the 1.3 ATA chamber and a 1.5 hour session in a 1.5 ATA chamber (where legal). I urge people to experiment with infrared mats and vibro acoustical speakers under the chamber. These really make the chamber a lot more enjoyable.
Also, having a dual valve cooler built into the chamber makes the session much more pleasant. For most people doing a session less than 1 hour, the oxygen is just getting saturated in the body. So if when getting out of the chamber, there is probably not going to be 4 hours of residual oxygen stuck in the cells.
Note: the positive effect of the hyperbaric chamber is what lasts 4 hours after the session.
Most people find that going in for 1.5 hours then letting the oxygen release for 4 hours then coming back into the chamber is much better than taking a 3 hour non stop session.
The moment someone steps out the tissues start to release the oxygen built up in all the cells.
After an hour of getting out of the hyperbaric chamber, the body is about 75% oxygenated
2nd hour about 50%
3rd hour about 25%
4th at nearly zero like it didn't even happen but the benefit was during the 6 hours. (2 hours in the chamber and 4 hours out). After 4 hours everything in the cells is back to where it was before entering the chamber.
Note: I had to revise this page due to manufacturer's not allowing me to list the protocols I use during an hour session. Most people that do hourly sessions do it on a daily basis. Those doing longer sessions are usually using the hyperbaric chamber to meet a time sensitive goal and are usually in a dire situation.