The effects of two kinds of mask (with or without exhaust valve) on clothing microclimates inside the mask in participants wearing protective clothing for spraying pesticides.

Aim: The study aimed at discovering the effects of wearing two types of protective mask on the clothing microclimate (temperature, humidity) inside the mask, physiological parameters and subjective sensations.

Method: Five healthy female students performed intermittent step exercise while wearing the protective clothing in a climate chamber at 28 degrees C and 60% relative humidity (RH). One mask was made of non-woven fabric and had no exhaust valve (mask A), and the other had an exhaust valve (mask B).

Results: (1) Clothing microclimate temperature inside the mask was significantly lower in mask B than in mask A. The final values were 35.5 +/- 0.3 degrees C in mask A and 34.6 +/- 0.8 degrees C in mask B. (2) Clothing microclimate humidity inside the mask was significantly lower in mask B than in mask A. The final values were 37.9 +/- 0.9 g/m3 in mask A and 35.7 +/- 2.0 g/m3 in mask B. (3) Cheek skin temperature inside the mask was kept significantly lower in mask B than in mask A. (4) Clothing microclimate humidity at trunk level increased more slowly with mask B than with mask A for four participants. (5) Rectal temperature increased more slowly with mask B than with mask A for three participants. (6) Tympanic temperature increased more slowly with mask B than with mask A for two out of four participants.

Discussion: We discussed these findings from the viewpoint that the dry and wet heat loss was accelerated through the nose under the influence of a reduced level of clothing microclimate inside mask B, having probably helped selective brain cooling by cooling more effectively the vein circulating blood through the nose.