referring now more particularly to the drawings , there is shown in fig1 a vehicle seat 10 having a generally horizontal seat rest portion 12 and an upright back rest portion 14 that is coupled to and projects upwardly from the seat rest portion 12 in conventional manner to support an occupant in a seated position on the seat 10 . the seat 10 is provided with an inflatable support system 15 according to the invention which includes one or more expandable chambers such as bladders or inflatable air cells 18 , 20 mounted at preselected location within the seat 10 , preferably at least on the ischial region wherein fluid inflatable bladder or air cells 18 are shown in fig1 and at the lower back or lumbar region of the backrest 14 wherein the fluid inflatable bladder or air cells 20 are shown . it should be understood that such locations are merely representative and the fluid expandable chambers can be placed in other seating locations such as bolsters , thorax regions and head rest regions ( not shown ). furthermore , such expandable chambers or fluid inflatable bladders or air cells can be located on other occupant supports such as mattresses and beds at spaced transversely disposed points thereon or where ever occupant support and heating is desired . while air cells are often used in such arrangements , the present invention can use fluids other than air to expand the expandable chambers . such fluids can include liquids such as water and anti - freeze compounds ; gases such as nitrogen , air , or other known inflatants . as shown in fig2 on or more of the expandable chambers or air cells 18 , 20 has two sheets or layers 22 , 24 of flexible plastic material , such as plastics , fabrics , or any other of the materials commonly used to construct inflatable fluid inflatable bladder or air cell for connection by tubes 27 to a pump 29 . the sheets 22 and 24 are imperforate . their perimeters 25 are sealed together by a heat weld , ribbon weld , radio frequency welding , adhesives or the like . the sheets or layers 22 , 24 are formed from flexible material , such as plastics , fabrics , or any other of the materials commonly used to construct inflatable fluid inflatable bladder or air cell . since the sheets 22 , 24 are both imperforate and sealed along their perimeters 25 , they are configured to form an internal cavity 26 . in the embodiment of fig3 the flexible material in the top layer 22 is located below known seat covering material . the top layer is formed from material comprised of electrically conductive materials such as carbon black or metal particles dispersed in polymeric material having a thickness of 0 . 010 inches to 0 . 050 inches . the polymeric material can be polypropylene , polyethylene , thermoplastic olefins and polyvinylchloride . other materials suitable for mixing with the conductive particles can include materials suitable for waste recycling such as polyurethanes . representative formulations and characteristics of such material are set forth in u . s . pat . nos . 4 , 954 , 695 ; 5 , 181 , 006 ; and 5 , 985 , 976 . the lower layer 24 is formed from a non - conductive material that is an electrical insulator such as a polyolefin material or any other polymeric material that is non - conductive and compatible for joining to the top layer 22 . the lower layer has a thickness in the range of 0 . 010 inches to 0 . 050 inches . in the illustrated embodiment of fig3 electrical leads 28 , 30 are connected by rivets 31 , 32 at spaced points on the perimeter 25 so that electrical current from a suitably controlled supply 33 can be directed across the top layer 22 for causing the conductive particles therein to produce a resistance heating action for warming the exposed surface 22 a of the top layer 22 of the expandable chamber such as fluid inflatable bladder or air cell 18 , 20 . in the embodiment of fig1 and 3 the fluid inflatable bladder or air cell are connected via suitable tubing to a controller 40 for a pneumatic seating comfort adjustment system of the type set - forth in u . s . pat . no . 6 , 088 , 643 commonly assigned and incorporated herein by reference . the controller has a manifold 41 comprising a housing 42 enclosing a chamber 42 a constructed with multiple outlet ports 44 for connecting the chamber 42 a to the inlet / outlet tubes of each individual cell or regional group of cells 18 , 20 . each outlet port 44 is provided with a control valve 46 for controlling the flow of fluid to and from one or more of the expandable chambers 18 , 20 . chamber 42 a is also constructed with a single inlet port 48 which is connected to a feed tube 50 to receive pressurized fluid , in this case air , from the pump 29 . pump 29 connects to a pump motor 54 connected to a pump drive 56 that is operated in response to air cell pressure under the control of a microcomputer 60 . a supply valve 62 is provided in feed tube 50 to control the flow of pressurized fluid to the manifold . the manifold can be molded of a high strength plastic or rubber material or other suitable material . the plastic material arrangement can have many of its components integrally molded therein . it is preferred that it be as compact and lightweight as possible . however , the invention can be configured with other than lightweight components and other than with integral components . a common bleed or exhaust valve 64 is provided to selectively release pressure from the manifold chamber 42 a through venting port 66 . the pressure in chamber 43 can therefore be adjusted by either actuating pump 52 or bleed valve 64 . while the control valves 46 can be under the control of a suitably programmed microprocessor it will be understood by those skilled in the art that the control valves could constitute one or more manually actuated control valves . still another arrangement could use the pump , operative alone , as the control of pressure in expandable chambers such as then one more fluid inflatable bladder or air cell 18 , 20 . in the embodiment of fig4 a fluid pressurized expandable chamber such as a bladder or air cell 70 is shown having spaced sheets 72 , 74 of suitable flexible material of the types set - forth below . they form one or more of the air cells of a suitable occupant support such as vehicle seating , furniture seating , mattresses or the like . a third shaped layer 76 is configured to overlie the upper sheet 72 . the layer 76 is comprised of electrically conductive particles dispersed in polymeric material having the same properties discussed with respect to the top layer 22 in the embodiment of fig3 . in this embodiment the expandable chamber 70 is supplied through a conduit 78 as in the case of the expandable chamber shown in the first embodiment . the expandable chamber 70 is not self heating . seat or occupant support surface heating , in this embodiment , is provided by connecting the third shaped layer 76 to a source of electrical power through leads 82 , 84 , respectively connected by suitable fasteners such as rivets 86 , 88 to opposite ends of the layer 76 . when it is desired to heat an occupant surface the leads are connect by a suitable controller or manual switching arrangement so as to produce electrical resistance heating for warming the upper surface 76 a of the layer 76 that is shaped between the occupant and the supporting configuration of the expandable chamber 70 . the disclosed embodiments are representative of a presently preferred form of the invention , but is intended to be illustrative rather than definitive thereof . the invention is defined in the claims .