A body support system having a top surface defining a head supporting region , a torso supporting region , and a foot and leg supporting region , comprising: a base defining a length and a width and a longitudinal axis; at least one breathing layer disposed over at least a portion of the base , said breathing layer formed of cellular polymer material having air permeability of at least 0.025 m 3 /sec/m 2 (5 ft 3 /min/ft 2 ), according to ASTM 737; at least one layer of reticulated viscoelastic cellular polymer material disposed over at least a portion of the at least one breathing layer corresponding to the torso supporting region of the body support system ; at least one support layer ( 216; 222 ) disposed between the base and the at least one reticulated viscoelastic cellular polymer layer , wherein the support layer (216; 222) defines a chimney cavity ( 218; 224 ), and cellular polymer material ( 220; 228 ) of greater air permeability than said support layer (216; 222) is held within said chimney cavity (218; 224); and at least one air flow unit located below the chimney cavity (218; 224) and below the torso supporting region and coupled to the at least one breathing layer for drawing air and/or moisture vapor through the breathing layer and the at least one layer of reticulated viscoelastic cellular polymer material and through the chimney cavity (218; 224) and away from the torso supporting region of the body support system , or for forcing air through the chimney cavity (218; 224) and the breathing layer and the at least one layer of reticulated viscoelastic cellular polymer material to the torso supporting region of the body support system . a base defining a length and a width and a longitudinal axis; at least one breathing layer disposed over at least a portion of the base , said breathing layer formed of cellular polymer material having air permeability of at least 0.025 m 3 /sec/m 2 (5 ft 3 /min/ft 2 ), according to ASTM 737; at least one layer of reticulated viscoelastic cellular polymer material disposed over at least a portion of the at least one breathing layer corresponding to the torso supporting region of the body support system ; at least one support layer ( 216; 222 ) disposed between the base and the at least one reticulated viscoelastic cellular polymer layer , wherein the support layer (216; 222) defines a chimney cavity ( 218; 224 ), and cellular polymer material ( 220; 228 ) of greater air permeability than said support layer (216; 222) is held within said chimney cavity (218; 224); and at least one air flow unit located below the chimney cavity (218; 224) and below the torso supporting region and coupled to the at least one breathing layer for drawing air and/or moisture vapor through the breathing layer and the at least one layer of reticulated viscoelastic cellular polymer material and through the chimney cavity (218; 224) and away from the torso supporting region of the body support system , or for forcing air through the chimney cavity (218; 224) and the breathing layer and the at least one layer of reticulated viscoelastic cellular polymer material to the torso supporting region of the body support system . <EOS>