Hi Lyn,
The manufacturer doesn’t indicate a pressure rating so I can’t guarantee anything, but I’ve tested them up to about 5 psi (350 hPa) myself and they showed no signs of stress.
For reference, a 170 lb (77 kg) weight distributed over an area of 12 x 18″ (30 x 45 cm) on an inflatable seat exerts about 0.8 psi (55 hPa) – quite a large safety factor.