An inflatable air blanket of the type adapted to treat hypothermia and the like is disclosed. The blanket comprises an air barrier layer, substantially impervious to airflow, and an underlying heat transfer layer adapted to permit penetration and diffusion of air therethrough. The barrier layer and heat transfer layer are joined together to form an envelope or chamber adapted for reception of warm air. The heat transfer layer may comprise a laminate-like non-woven web structure with outer layers thereof including a bonding material disposed in a reticular pattern thereon. Air from the envelope or chamber penetrates and uniformly diffuses through the heat transfer layer to gently impinge upon the treated patient.