23 inch: If a very small kid is using it they don't need the room of a larger hyperbaric chamber. With a 23 inch chamber, a larger person usually feels claustrophobic if they are normally claustrophobic. Someone that is not normally claustrophobic and doesn't need more head room won't usually have an issue. It's tight but you can bring a laptop or a book in the 23 inch chamber. You cannot turn around and move to the other side. You can't stretch and touch your toes or exercise in the 23 inch chamber. The Shallow Dive by summit to sea is the best option as long as you don't get cramped easily because you won't be able to stretch. Positional in tolerant people usually have a problem. A parent and a small kid can go in it but it will be super tight. Buying a 23 inch chamber should only be bought in extreme situations where someone doesn't have enough money to buy a larger one or cannot afford to rent one. If someone truly cannot afford the standard rental price I will only rent these models on sliding scales. These usually have about 40 square feet of material to produce the chamber.
The cheapest hyperbaric chamber that is sold is the Shallow Dive which is 23 inches which is.The small ones usually just have one window at the end. (the New Shallow Dive is now out and is larger and has 2 air intake valves. The older 23 inch model is now upgraded.
27 to 28 The chambers in this range are usually about 8900 to 12,000 dollars. These have enough room to move around in but not enough to really workout in. For someone who is claustrophobic that cannot go in the small size, this hat more than enough room. These usually have 2 to 3 windows. These usually take up about 26 linear feet of welded seams and take about 4 days to manufacturer. These also take about 70 square feet of material to produce the chamber.
28+ The chambers in this category have enough room for someone to move around, workout, basically live out of. Chambers over 28 inches are for two people that can get cramped in the 27 to 28 inch chambers. These usually have more windows and cost the most as there is more labor involved in making them.