Impurities can be prevented from penetrating into the plasma core in JET ELMy H-mode discharges if the deuterium gas puff exceeds a certain level. In this was explained by noting that the neo-classical convective velocity within the edge transport barrier changes from inward- to outward-directed when the deuterium density at the last closed flux surface exceeds a critical level, which is reached by increasing the deuterium gas puffing. However, it is also true that for the impurities to reach the last closed flux surface they first have to penetrate the Scrape-Off Layer (SOL). The goal of this paper is to evaluate other processes, within the SOL, which can also contribute to impurity screening along with the neo-classical convective velocity within the Edge Transport Barrier (ETB).