The combined effect of temperature, relative humidity and work intensity on human strain in hot and humid environments

• We built a climate chamber to simulate hot and humid environments.
• We proved the existence of combined effect caused by temperature and humidity.
• Combined effect of temperature, relative humidity and work intensity was quantified.
• The enthalpy was adopted to reflect the environment intensity.
• The combined effect of enthalpy and work intensity was quantified.

Hot and humid environments are prevalent in certain workplaces, such as deep mines, aviations, military facilities and so on. When working in these environments, heat strain may be produced on the human body, and the work productivity and human health will be affected, so it is necessary to study the impact mechanism caused by the influencing factors on the human body. In this paper, a climate chamber was built to simulate the hot and humid environments. The multiple regressions of physiological parameters related to temperature and relative humidity were obtained, and the combined effect caused by temperature and relative humidity on the human physiological responses was proven. The values of combined effect, temperature effect and humidity effect were quantified, and then the work effect was added. Finally, considering the combined effect between temperature and relative humidity, the enthalpy of air was adopted to reflect the effect of these two environment factors comprehensively. The study in this paper helps people understand the effects caused by environment and work intensity on human strain better and it provides a practical method for the future research.