Comfort Curve in HVAC

From the perspective of HVAC, there are four factors that affect the comfort and well-being of occupants in a space: temperature, humidity, airflow pattern, and the cleanliness of the air within that environment. To achieve complete comfort, each of these factors must be at its optimal level. For instance, temperature—the most significant factor—affects heat transfer through convection and radiation. Humidity has a considerable effect on skin evaporation and overall body comfort. Low humidity dries out the skin and respiratory tract, leading to coughing and other discomforts. On the other hand, high humidity not only has adverse physiological effects and causes skin odor but can also damage many materials in the environment. Studies show that, in general, the most suitable conditions for the human body are 23°C with 50–60% humidity in summer, and 22°C with 50% relative humidity in winter. Air movement across the body helps remove heat and moisture from the skin surface. The recommended airflow velocity is approximately 0.1 m/s; excessive airspeed can cause discomfort and reduce overall comfort. Finally, an adequate supply of oxygen and low levels of dust, smoke, carbon dioxide, and other airborne pollutants play a crucial role in human comfort and health.