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Respiratory protective devices are used to protect workers from inhalation of hazardous atmospheres. Beside the aspects related to adequacy of the device in protecting the worker, it is necessary to investigate also the aspects related to the suitability of the device such as ergonomic factors: one of the most common complain of the workers is related to the face thermal sensation perceived as hot.In this study, the effect of a power assisted filtering device incorporating a full face mask on the thermophysiological response of a thermal manikin is investigated.The experimental protocol schedules tests on a standing sweating thermal manikin (Newton) in the climatic chamber, where hot conditions were simulated (air temperature at 34°C, relative humidity at 32%). Two conditions were tested: manikin with the respirator powered on (CR) and manikin without the respirator (CC). Two different levels of metabolic rate were set (1 MET and 3 METs).Results show:at 1 MET the manikin is in thermal balance with the external environment with or without respirator.at 3 MET, although the thermoregulation system is very stressed (the rectal temperature increases continuously with or without respirator), the effect of the respirator produces a small decrease of the local and global temperatures and also of the amount of sweat generated by active thermoregulation that reaches its maximum value of 30 g/min in CC). The body reaches sensation between ‘hot’ (CC) and ‘warm’ (CR) while the face sensation increases rapidly reaching the value correspondent to ‘very hot’ both for CC and CR.At M=1 MET and M=3 MET the effect of the hot environment is weakened by the action of the respirator which allows a continuous heat exchange removing and renovating the air layer around the face without providing an additional thermal load.