Air mattress

An air mattress, comprising:

• a first through a fourth flexible sheets which are stacked in the order mentioned and bonded together along the peripheries thereof so as to be sealed, wherein
• said first and second sheets are bonded together at a multiplicity of first bonding spots thereof spaced apart along longitudinal and transverse lines at regular intervals such that four neighboring bonding spots occupy four corners of a tetragon;
• said second and said third sheets are bonded together at a multiplicity of second bonding spots thereof at locations which correspond to the centers of said tetragons;
• and
• said third and said fourth sheets are bonded together at a multiplicity of third bonding spots thereof at positions which correspond to said multiplicity of first bonding spots;
• wherein
• said first and second sheets define a first air cell, said second and third sheets define a second air cell, and said third and fourth sheets define a third air cell;
• a first inlet/outlet tube communicating only with the first air cell;
• and
• a second inlet/outlet tube communicating only with the second air cell.