When working with probes in tokamak plasmas, impurities are always an annoyance. However deliberate seeding with light impurities has shown features which are favourable for a nuclear fusion tokamak reactor, such as high confinement at high density with a radiating belt [1]. Argon and neon have been seeded into a variety of discharge configurations on JET. In these discharges the density build up is produced by a strong gas-puff of D2, ("puff" phase, see Fig. 1), during which the confinement is degraded. At the same time an impurity is seeded, e.g. argon, in order to raise the radiation level. However the confinement recovers again when the gas valve is closed ("afterpuff" phase). To maintain the density in this phase, small levels of D2 are applied in addition to a modest extra amount of argon. In discharges limited on the septum of the MkIIGB divertor, this leads to quasi-stationary plasmas at high densities close to the Greenwald level and simultaneously good confinement (H97 1). The overall confinement properties of impurity seeded H-mode discharges are discussed in [2]. A new confinement scenario is only attractive as a possible operation scheme, when also the effects caused by ELMs can be handled. Therefore first the link between the global confinement and ELMs will be explored, and then results on changes in the SOL power flux will be given. The afterpuff phase will be the focus of this analysis, since its good confinement properties are particularly attractive. The impurity seeded in the pulses presented here was exclusively argon. A few comparisons of seeded with unseeded puff phases are shown for an enhanced high triangularity configuration.