Effects of ventilation openings in industrial safety helmets on evaporative heat dissipation

摘要

Objectives : This study aimed to investigate the effects of ventilation openings in commercial industrial safety helmets (ISHs) on evaporative heat dissipation. Methods : Seven models of commercial ISH were examined quantitatively by a sweating thermal head manikin (SHM) with six separate zones. To simulate summer outdoor conditions, the measurements were done in a climate chamber, with the room temperature and relative humidity set at 34.0°C and 50%, respectively. The shell temperature of SHM was set at 34.0°C. Wind was blown from the front or left side at 1.0, 2.0, and 3.0?m/s. The necessary heat flux to keep the manikin skin temperature at 34.0°C was counted as evaporative heat dissipation in each zone. Results : Openings at the front and back, and openings between the body and brim of the helmet played a significant role in increasing the heat flux in Forehead zone, but in all zones as a total, the effects were not significant. Heat flux for ISH with openings on both the right and left sides was not significantly different from that without openings. Conclusions : Our study utilizing SHM showed that ventilation openings on both the right and left sides or front and back sides of commercial ISHs were not significantly effective in increasing total evaporative heat dissipation under an equivalent temperature of ambience and manikin shell. Further improvements on ISH are needed to increase evaporative heat dissipation.