Windows are the most expensive part of the chamber to make. It takes about 500 dollars in materials and labor to produce one window. This is why a chamber with 3 windows can cost at least 1500 just for the windows. The cheapest chambers that are FDA cleared have one window. When looking at the windows, the 5 ply windows usually are the highest priced. Three ply is what is usually standard in hyperbaric chambers. But if the chamber is not going to be used 8 hours a day and for home use, 5 ply can be over kill unless its in a clinic.
The windows from different hyperbaric companies often will have their own proprietary blend of window material. Hyperbaric chambers can have either urethane windows or they can be made of "plexiglass".
Note: There are windows that can be one layer thick or 5 thin layers put together. A good thing to know is the ratio of the window materials being used. Some companies have only 3 layers of urethane but have only one layer of plexiglass and some of 100% plexiglass and others 100% urethane. This can mean the difference between a chamber that costs around 10,000 dollars and another under 5,000 dollars. Windows have to be perfect, all the air bubbles smoothed out, and depending on the window, it can cost a lot depending on how may rejects are thrown away to make the perfect window. If you don't want a lot of windows, it can decrease the price significantly.
Questions to ask about windows:
How many windows are in the hyperbaric chamber? This adds the biggest expense to the chamber.
What is the size of the windows? Some can have many windows but they are much smaller.
Where are the windows located?
Do the windows build up with condensation? What's the purpose of a window if you can't see out?
Can you monitor the pressure gages through the windows?
How many ply are the windows. (some are just one ply and others 4 or more)
What material is it? Urethane or plexiglass?