APPROVED FOR PUBLIC RELEASE

It is well accepted that wearing a respirator increases the physiological load imposed on the user. However, there is little quantitative evidence of the impact of respiratory protection on thermal strain imposed on the user as a function of the total individual protective ensemble (IPE). This pilot study aims to use the novel technique of Thermal Imaging (TI) to assess the heat status of the face and thermal strain associated with wearing the S10 respirator. The physiological (rectal and tympanic temperatures, heart rate), psychophysical (thermal sensation and discomfort, perceived exertion) and thermal effects (thermal imaging) of the S10 respirator were measured in four healthy males (31±4.5yrs). Each subject completed two 45 min trials consisting of acclimation (10 min), treadmill walking (30 min) and rest (5 min) in a hot environment (30°C dry bulb and 60 % relative humidity), while wearing the UK MK IV overgarment with the S10 respirator (MASK) and without (CON). Generally, there was no additional thermal strain while wearing the S10 respirator. However, subjects reported thermal discomfort of the face as being significantly (p<0.05) more uncomfortable after 30 mins of exercise compared to being unmasked. In conclusion, the mask partially inhibited evaporative cooling of the face giving the user the perception of being more heat stressed than when unmasked, which was not matched by the recorded physiological strain. It is recommended that the design of the respirator require no significant alteration to reduce any perceived thermal load. RELEASE LIMITATIO