AbstractA countercurrent thermal VOC desorber apparatus with 0.43 to 0.67 lb/hr (0.195 to 0.304 kg/hr) activated carbon flow and 0.43 to 0.49 scfm (0.88 to 1.00 kg/hr) purge air flow provided 26.6 to 77.7% VOC desorption efficiency over the 62 to 199°F (16 to 92°C) operating range. The VOC concentration of the carbon was measured at the carbon inlet, outlet, and two intermediate points in the desorber by thermogravimetric analysis. Inlet adsorbent carbon VOC concentrations ranged from 0.23 to 0.44 grams VOC/gram carbon. The VOC concentration of the purge air was measured at the purge air outlet and two points within the desorber by GC‐FID. The VOC concentration of the outlet purge air ranged from 14,627 to 44,209 ppm (0.023 to 0.070 grams VOC/gram air). The VOC concentrations measured in the activated carbon and in the purge air provided the oprating line data for plotting on an X‐Y diagram and together with the equilibrium isotherms resulted in mass transfer coefficients Kga in the 472 to 864 lb/ft3hr (7,561 to 13,840 kg/m3hr)