The biggest difference between steel chamber hyperbaric therapy devices and inflatable ones is the atmospheric pressure and quality of oxygen being administered. In hard chambers, pressure is set between 2.4 - 3.0 ATA, three times the pressure of ambient air. This increase in pressure allows oxygen to enter the bloodstream at 1,824 mmHg (normal air pressure is 157mmHg).
In most soft chambers, pressure only reaches 1.3 ATA. Bacteria is hindered from growing at a minimum of 1.5 ATA. In addition, the lower pressure results in a much milder absorption of oxygen. Compared to the 1,824 mmHg absorbtion of hard chambers, the arterial oxygen of a soft chamber at 1.3 ATA is 230 mmHg (again, normal air pressure is 157mmHg).