Prediction Of Safe Working Hours Of Sanitation Workers Coupling ENVI-met And Thermal Regulation Model

Under the dual influence of global warming and rapid urbanization,the intensity and frequency of extreme heat wave events have been significantly enhanced,and the risk of heat safety in outdoor environment has increased.Sanitation workers,due to their occupational peculiarities,are exposed to long hours of outdoor high-temperature environment working in summer and suffer from greater physiological safety risks.The prediction method of safe working hours proposed in this paper can be used for risk assessment of sanitation workers’ high-temperature working,provide theoretical guidance for the development of sanitation work-related standards.The main contents are as follows.Firstly,a subjective survey of outdoor high-temperature working was conducted in terms of basic information,labor organization and working environment of sanitation workers,and it was found that front-line sanitation workers have an older age profile;sanitation workers have long hours of outdoor high-temperature workings,lower education level,lack of self-health protection awareness,and insufficient awareness of heat stress risks;workers’ subjective heat sensation,heatstroke prevention measures and high-temperature working fatigue and other factors showed large individual differences.Secondly,based on the two-node physiological heat regulation model,the basal metabolic rate,body surface area,sweating rate and blood flow rate were improved according to individual differences,and the clothing system parameters and related heat transfer coefficients were improved according to outdoor solar radiation and wind speed,and introducing external work expressed in terms of mechanical work efficiency and modified basal metabolic rate.A physiological thermoregulatory model applicable to sanitation workers working outdoors was developed and the robustness of the proposed model was verified.The results showed that the model could reliably predict the changes of physiological parameters in different individuals in different thermal environments.Finally,ENVI-met and thermal regulation model to study the changes of sanitation workers’ physiological parameters over time,combined with the safety thresholds of human physiological parameters in high-temperature environments to predict workers’ safe working hours and individual differences.The study showed that the working hours with core temperature as the safety index were: evening shift >morning shift > noon shift,and the working hours with water loss as the safety index were: morning shift > evening shift > noon shift;under the same working condition,both core temperature and water loss of male workers reached the safety threshold12-15 min earlier than female workers;the core temperature and water loss are inconsistent in judging the safe working hours of workers due to the age factor.For workers over 52 years old,the core temperature has long exceeded the human thermal tolerance limit when the water loss reaches the safety threshold,while for workers under 52 years old,the core temperature is more hazardous when it reaches the safety threshold.