In the context of the French DIMITRHY project ANR-08-PANH006 experiments have been carried out to measure helium injections in a cubic 1 m3 box - GAMELAN in a reproducible and quan- titative manner. For the present work, we limit ourselves to the unique configuration of a closed box with a small hole at its base to prevent overpressure. This case leads to enough difficulties of modelisations to deserve our attention. The box is initially filled with air, and injections of helium through a tube of diameter 20 mm is operated. The box is instrumented with catharometres to measure the helium volume concentration within an accuracy better than 0.1%2 We present the CFD (Fluent and CASTEM, ANSYS-CFX and ADREA-HF) calculations results obtained by 5 different teams participating to the benchmark in the following situation: the case of a plume release of helium in a closed box (4NL/min). Parts of the CFD simulations were performed in the European co-funded project HyIndoor, others were performed in the french ANR-08-PANH006 DimitrHy project.