Experimental Study On The Use Of Cooling Vests To Alleviate Heat Stress Of Outdoor Workers

Facing the sudden outbreak of the COVID-19 pandemic,a large number of medical workers are called up to work for a long time in outdoor high-temperature environments with dressing medical protective clothing.However,the medical protective clothing will influence the medical worker’s heat dissipation,although it could isolate the virus.And this seriously increases the risk of medical workers suffering heat strain,pushing their physiology and psychology to a dangerous status.Although human thermal comfort in outdoor environments with high temperatures has been widely studied,it still needs to focus on how to decrease the heat strain and ensure the workers’ physiology and psychological safety when they are working in high-temperature environments with dressing personal protective devices.In this study,ice bag cooling vests were used to cool subjects wearing medical protective clothing to effectively reduce heat strain.Eighteen subjects(9 males and 9females)were recruited to participate in the experiment in a temporary tent set up in an open-air experimental site to simulate the real working environment of an outdoor healthcare worker,and each subject randomly participated in three heat exposure experiments.The three experiments stand for three cooling vest modes,i.e.,no cooling vest,and two types of cooling vests with different cooling areas.The physical parameters such as air temperature,relative humidity,black bulb temperature,etc.and the physiological parameters such as skin temperature,heart rate,and core temperature(cochlear temperature),etc.were monitored.Subjected votes on thermal sensation,thermal comfort,and humidity sensation were collected.Subjects’ feedback about their discomfort symptoms and their sensations to the wet body parts were also collected.Based on the data obtained,the actual effect of the cooling vest on the physiological and psychological parameters of subjects wearing medical protective clothing in hot outdoor environments was assessed and the effect of gender differences on the cooling effect when using the cooling vest was compared.Results showed that the cooling vest was effective in reducing the average skin temperature and sweating of the subjects,although the effect of the vest on heart rate as well as core temperature was not significant.The effect of wearing a cooling vest on the improvement of discomfort symptoms such as breathlessness was significant,and the improvement in heat sensation and thermal comfort was more significant at the beginning of heat exposure,with the improvement gradually weakening over time.The cooling vest was effective in improving the perception of sweating in the chest,abdomen and back,which are the main areas of sweating when not cooled.The cooling vest had a stronger cooling effect on females’ skin than on males and improved sweating more in males than females,while no gender differences were shown in the effects on heart rate and core temperature.The overall thermal sensation of the female was significantly lower than that of the males at the beginning of the use of the cooling vest,with the difference diminishing with increasing time of heat exposure.Analysis of the experimental data revealed significant correlations between local and overall thermal sensation and between local skin temperature and overall thermal sensation in the subjects,with back cooling reducing the overall thermal sensation of the subjects more.A strong correlation was found between cooling coverage(the ratio of cooling area to body surface area)and overall thermal sensation.The results show that when the cooling coverage reaches 15.6%to 18.8%,the overall thermal sensation of personnel in high temperature and high humidity environments can reach a neutral level.From the experiments,it can be concluded that cooling vests can reduce heat strain and improve thermal comfort for personnel working in protective clothing in outdoor high-temperature environments.The risk of overcooling can be reduced by selecting a cooling vest with different cooling areas according to the body surface area of the personnel and gradually increasing the cooling area according to the heat exposure time.The results of the study can provide a reference for further design of personal cooling clothing and have good theoretical and practical application value.