The MYRRHA project aims at the construction of a new research reactor in Mol (Belgium) to demonstrate the nuclear waste transmutation feasibility with an Accelerator Driven System (ADS). In its subcritical configuration, the MYRRHA facility requires a proton beam with a maximum power of 2.4 MW (600 MeV - 4 mA). Such a continuous wave beam will be delivered by a superconducting linear accelerator (linac) which must fulfil very stringent reliability requirements to ensure the safe ADS operation with a high level of availability. The linac injector will be composed of: a proton source, a low energy beam transport line (LEBT), a 176 MHz RFQ and CH-DTL cavities. The LEBT prototype has been built and is presently installed and operated at LPSC Grenoble (France). An experimental program, to optimise the tuning of the line, the beam transport, and to study the space charge compensation mechanism, is in progress. We here review the main achievements of the LEBT commissioning. Experimental results will be presented and discussed, in particular the influence of the residual gas (type and pressure) on the beam dynamics.