Firefighter protective clothing helps to defend the wearer against the harsh conditions experienced during fire response activities. The equipment worn by firefighters and the physically demanding nature of their work often pulls the material of the firefighter protective clothing taunt, removing air gaps between the layers of materials. This significantly decreases the effectiveness of the garments and can lead to contact burns on the skin. The concept of a temperature activated shape memory material has been applied to the garments to combat this issue. A computer program has been developed to analyze the heat transfer through different layers of materials. The program is capable of approximating the effects of a variable air gap in the garment which would result from the implementation of the temperature activated shape memory material. Experiments and computer simulations confirm that a variable air gap improves the thermal performance of firefighter protective clothing.