For many vacuum processes the rate of recovery to a specific base pressure after gas injection is used as a criterion for determining the cleanliness of the vacuum system. When a cryopump is used, a long recovery time does not necessarily mean that undesirable gas species are present, because the recovery time of the cryopump itself increases as it becomes loaded with gases. This paper reports on experimental measurements of recovery time for APD‐8 Cryopumps after flowing Ar and H2at different rates for extended periods of time. Tests were run to measure the effect of using a new supercarbon versus standard charcoal and to see the effect of the cryotrapping of H2by Ar without the use of charcoal. The recovery time after injecting Ar correlates with the time for the surface temperature of the solid Ar to return to base temperature. The recovery time for H2is a function of the amount of H2that has been pumped, cryopanel temperature, type of charcoal, gas flow rate, H2concentration, and sequence of gas injection.