A standard predictive index of human response to the thermal environment is presented, focusing on three key indices: ASHRAE's Effective Temperature (SET*), Fanger's Predicted Mean Vote (PMV), and Winslow's Skin Wettedness Index (DISC). SET* is defined as the dry bulb temperature of an isothermal environment at 50% RH where a subject would have the same skin wettedness and heat exchange as in the actual environment. PMV is based on the heat load required to restore comfort, while DISC measures thermal discomfort based on skin wettedness. Both PMV and DISC are similar at average humidities but differ at extreme humidities. A new index, PMV*, is proposed by replacing operative temperature in Fanger's Comfort Equation with SET*. PMV* is shown to be a better indicator of heat stress and strain in various environments. The paper discusses the physiological and thermal mechanisms underlying human response to the environment, including energy exchange, sweating, and skin wettedness. It outlines the heat balance equation and the factors influencing thermal comfort, such as clothing insulation, air movement, and humidity. The paper also introduces a new Comfort-Humidity chart based on PMV*, which provides a more accurate representation of thermal comfort than traditional charts. The paper concludes that PMV* is a more comprehensive index of thermal comfort and heat stress than PMV or DISC, as it accounts for both environmental conditions and physiological responses. It also highlights the importance of considering humidity and clothing permeability in assessing thermal comfort. The paper provides a detailed explanation of the heat balance equation and the factors influencing thermal comfort, as well as the practical applications of PMV* in HVAC systems and environmental design. The paper emphasizes the need for a unified approach to thermal comfort assessment, combining physiological, physiological, and sensory factors to better understand human response to the thermal environment.A standard predictive index of human response to the thermal environment is presented, focusing on three key indices: ASHRAE's Effective Temperature (SET*), Fanger's Predicted Mean Vote (PMV), and Winslow's Skin Wettedness Index (DISC). SET* is defined as the dry bulb temperature of an isothermal environment at 50% RH where a subject would have the same skin wettedness and heat exchange as in the actual environment. PMV is based on the heat load required to restore comfort, while DISC measures thermal discomfort based on skin wettedness. Both PMV and DISC are similar at average humidities but differ at extreme humidities. A new index, PMV*, is proposed by replacing operative temperature in Fanger's Comfort Equation with SET*. PMV* is shown to be a better indicator of heat stress and strain in various environments. The paper discusses the physiological and thermal mechanisms underlying human response to the environment, including energy exchange, sweating, and skin wettedness. It outlines the heat balance equation and the factors influencing thermal comfort, such as clothing insulation, air movement, and humidity. The paper also introduces a new Comfort-Humidity chart based on PMV*, which provides a more accurate representation of thermal comfort than traditional charts. The paper concludes that PMV* is a more comprehensive index of thermal comfort and heat stress than PMV or DISC, as it accounts for both environmental conditions and physiological responses. It also highlights the importance of considering humidity and clothing permeability in assessing thermal comfort. The paper provides a detailed explanation of the heat balance equation and the factors influencing thermal comfort, as well as the practical applications of PMV* in HVAC systems and environmental design. The paper emphasizes the need for a unified approach to thermal comfort assessment, combining physiological, physiological, and sensory factors to better understand human response to the thermal environment.