A mattress has cells with low air permeability envelopes. Check valves permit air flow into cell groups. An inflation structure expands within the cells when not loaded to cause the envelope to fill with air through the check valves. Another mattress has a cell with a primary bladder, a hollow inflation structure in the primary bladder, a secondary bladder in the hollow inflation structure. The inflation structure expands when not under load to cause the primary bladder to fill with air through the check valve. An air cell has a bladder, a check valve permitting air flow to the bladder, and an inflation structure that expands in the bladder when not under load to cause the bladder to fill with air through the check valve. The inflation structure is a cylindrical foam structure with a portion removed along a surface and a D-shaped hollow space within an upper portion thereof.