How to choose a chamber.

1. Pressure: read the unit, not the headline.

Pressure is measured in ATA (atmospheres absolute). Home soft-shell chambers typically operate around 1.3 to 1.5 ATA. Hard-shell clinical chambers can go much higher; OxyHealth's Fortius 420, for example, lists up to 4.0 ATA. A brand may advertise a higher number than the specific model delivers, so ask for the rated operating pressure of the exact unit.

2. Soft shell or hard shell.

Soft-shell (inflatable) chambers are portable and far less expensive, but run at lower pressures. Hard-shell chambers are heavier, costlier and can reach higher pressures. Higher-pressure use is typically a clinical decision made with a physician, not a lifestyle purchase.

3. FDA status: ask for the number.

"FDA cleared" means a specific 510(k) submission was cleared for specific uses. Ask for the K-number for the exact model and look it up in the FDA's database. In our audits, no OxyHealth product page published one. Also note that clearance covers defined medical uses; the FDA has cautioned consumers about unproven claims for other uses.

4. What's in the box, and the real total cost.

Compare what each system includes: compressor, hose, mattress, jacket, frame, and any oxygen concentrator. Ask about delivery, setup, replacement parts and who services it. Many manufacturers don't publish prices at all, so get a written quote.

5. Warranty and support, in writing.

Terms vary from two to five years, and some pages don't state one. Ask who is on the other end when something fails, and whether the warranty covers parts and labor.

Red flags worth walking away from

• No FDA number available on request.
• The same chamber described at different pressures in different places.
• Cure claims, or benefits promised for conditions without trials to back them.
• No price, warranty or service terms until after a hard sell.

Before any of it, ask a physician.

Hyperbaric oxygen is a medical treatment with real risks. Whether it suits you, at what pressure and how often, is a question for a licensed physician.