A liner bag for use with a warming device has an inner bag and an outer bag. The inner bag has an inner chamber for receiving and at least partially enclosing a container. The outer bag has an outer chamber that at least partially encloses the inner bag and that receives and encloses a heat transfer fluid that transfers heat to the container. The side edges of the inner bag are joined to the side edges of the outer bag but the front face, rear face, and bottom edge of the inner bag are not joined to the front face, rear face, and bottom edge of the outer bag so that the heat transfer fluid may flow between the outer bag and inner bag for more effectively transferring heat to the inner bag and the container enclosed in the inner bag. The liner bag may also have an anti-microbial agent for disinfecting the heat transfer fluid placed in the outer bag.