Psychrometric Graph [portable] Today

These are straight vertical lines (or horizontal, depending on the chart's orientation). They represent the sensible heat level of the air—the heat you can feel.

Air is invisible. Yet, for heating, ventilation, and air conditioning (HVAC) engineers, it is a complex mixture of gases, water vapor, and energy. To visualize this invisible world, engineers rely on one of the most elegant and powerful tools ever developed: The Psychrometric Chart . psychrometric graph

This is the temperature at which the air becomes saturated (100% RH) if cooled at constant pressure. To find it, move horizontally left from your point to the saturation curve. These are straight vertical lines (or horizontal, depending

These are sweeping parabolic curves. Each curve represents a percentage of saturation (0% to 100%). The 100% RH line is the Saturation Line . Air cannot hold more moisture beyond this line; it will start to condense (dew, fog, rain). Yet, for heating, ventilation, and air conditioning (HVAC)

The term comes from the Greek psukhros (cold) and metron (measure). While it measures "cold," its real power lies in measuring change. To read the chart, you must identify its seven fundamental components. Most charts are plotted with Dry Bulb Temperature (the temperature your thermometer reads) on the horizontal axis.