Example 2.2. An HVAC&R operator measured the dry- and wet-bulb temperatures in an air conditioned space as 75°F (23.9°C) and 63°F (17.2°C), respectively. Find the relative humidity of this air conditioned space by using ASHRAE’s chart and by calculation. The humidity ratios of the saturated air at temperatures of 75 and 63°F are 0.018809 and 0.012355 lb / lb (kg / kg), respectively.