The deployment of networks composed of several radio frequency (RF) based wireless power transfer nodes will be an indispensable component of future Internet of Things (IoTs). The natural objective of such networks, so called the wireless power transfer networks (WPTNs), is to charge the energy receiver devices wirelessly as quickly as possible; i.e. maximizing the transmitted power. However, a safe-charging WPTN must also comply with the RF exposure regulations and keep electromagnetic radiation (EMR) under a predefined threshold. In this paper we consider the problem of maximizing the transmitted wireless power to the energy receivers with subject to the safety constraints. We introduce two fully-distributed charging algorithms where the energy transmitters communicate only with the sensors in their communication range to obtain their measurements, perform simple computation steps to adjust their power levels and and in turn satisfy safety constraints without any global information. (C) 2017, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.