  A simple yet highly reproducible method to suppress contamination of graphene
at low temperature inside the cryostat is presented. The method consists of
applying a current of several mA through the graphene device, which is here
typically a few $\mu$m wide. This ultra-high current density is shown to remove
contamination adsorbed on the surface. This method is well suited for quantum
electron transport studies of undoped graphene devices, and its utility is
demonstrated here by measuring the anomalous quantum Hall effect.
