In most Rapid Compression Machine (RCM) operations, it is sought to have a homogeneous temperature field inside the core region of the reaction chamber so that the adiabatic core assumption may be appropriately applied. Pistons with crevice on their side have shown to be effective in producing a uniform temperature field at the end of the compression. Although the efficiency of the crevice to produce a homogeneous environment is highly dependent on the operational conditions (pressure, temperature, gases composition, compression time, etc.), crevice designs are seldom adapted to the intended experiments. This is problematic as there are potentially many experiments which do not respect the conditions to obtain a uniform temperature field required to correctly interpret the data. Actually, no method other than CFD simulations has been proposed to this day to validate a specific crevice design, which is in practice most often an obstacle to the systematic validation of crevices. The model proposed in this study aims to fill this gap in allowing to check if a crevice design yields a homogeneous temperature field in the considered operational conditions. It is observed that as soon as a critical mass is transported from the chamber to the crevice, the crevice fulfills its role and guarantees the temperature homogeneity of the core region. The two key findings of the present work are therefore to be able to predict this critical mass for any possible configuration, and to propose an easy method to assess whether a specific crevice volume ensures this critical mass to be effectively sucked from the chamber. The whole process proposed in this study could then be applied as a certification of crevice design prior to any RCM experimental campaign. (C) 2018 The Combustion Institute, Published by Elsevier Inc. All rights reserved.