Future low cost wireless networks are expected to provide high data rates with low power consumption. A dense deployment of distributed small-cells, within the existing network infrastructure, is one of the candidate solutions to achieve this goal. Unfortunately, the aggregate signal resulting from the transmission of these multiples small cells can be considered as an electromagnetic (EM) pollution for passive users who do not carry wireless devices. These users are victim of primary electromagnetic ”smokers” and request from operators to be spared from these new base stations. The aim of this contribution is to propose an electromagnetic friendly environment with minimum EM pollution, while satisfying the quality of service requirements. The technique employed, called Distributed Space-Time Reversal (DSTR), focuses the energy on active users (equipped with wireless devices) and is able to spare passive users from EM waves. In this contribution, we provide a theoretical analysis of the technique and show the impact of active/passive users with respect to the number of cells.