Getting exposed to a flash fire can be a deadly situation until the worker manages to escape from the fire location. The movement of the worker induces his protective clothing to move periodically inwards and outwards with respect to the body, which significantly influences the protective performance of the clothing. In addition, fabric properties, particularly, fabric thickness and backside emissivity have also a crucial effect on heat release from the clothing to the body and eventually on the protection provided by the clothing. This paper investigates the effect of a variation in the thickness of Kevlar®/PBI form 0.3 mm to 1.8 mm and a variation in its backside emissivity from 0.9 to 0.1 on the protective performance of the fabric for a mean air gap of 3 mm between the clothing and body and a periodic motion amplitude ranges from 0.5 mm to 3 mm and a periodic motion frequency ranges from 0 rps to 4 rps. The results showed that the improvement in the clothing protective performance made by increasing the fabric thickness and/or decreasing the fabric backside emissivity is boosted by increasing the periodic motion frequency and reduced by increasing the periodic motion amplitude.