With a sweating manikin, the heat exchange efficiency through firefighter turnout clothing system from the wearer to the environment and the effects of material component and design feature on heat transfer were evaluated in a climatic chamber. Material component and design feature were varied to measure thermal insulation (It — in clo units) and moisture permeability index (im — dimensionless) of firefighter turnout clothing under two circumstances, with openings at the neck, wrists, waist and ankles sealed or not. Two new indices CIt and Cim were proposed to evaluate heat and moisture transfer capabilities of firefighter turnout clothing, which were defined as the changing rates of It and im from conditions of the clothing dressed in a regular way with openings unsealed to the openings sealed. The results showed that CIt indicated the effects of clothing design differences on heat transfer through firefighter turnout clothing, while Cim was dependent greatly on material properties (moisture permeability).