Tourism is a growing concern for the conservation of heritage sites. In the Dordogne, the Cap Blanc shelter attracts many visitors and their presence may affect its parietal frieze by altering the thermal environment. To assess this impact, a study is carried out using numerical simulation, a non-intrusive conservation tool that can model the thermal behaviour of the cavity during tourist visits. We validate the numerical model with the temperature measurements taken inside the shelter during three tourist visits. We show that the heat emitted by the tourists is mostly absorbed by the walls, resulting in a small increase in air temperature (between 1°C and 2°C) and a large temperature gradient near the walls during the visits, which favours condensation and possible conservation problems.