A new method of humidification and heat controls for a PEM fuel cell stack using non-contact laser absorption spectroscopy is presented in this study. The focus of this experiment is to follow the load current variation and its effect on the resistance and performance. Optimal relative humidity gases not only decrease the total losses in the membrane-electrode-assembly (MEA), but also eliminate channel flooding. By controlling humidified air and heat, it is shown that the tested stack has an improvement in performance as compared to fully humidified gases especially under a heavy-load condition. In this paper, a proposed humidification and temperature control strategy based on humidifiers and gas heaters is presented and discussed in detail. The results indicate that the humidification and temperature control strategy suggested in this experimental study can precisely control the air relative humidity, temperature and flow rate, and increase overall power output by 16% from PEM fuel cell stack. (c) 2012 Elsevier Ltd. All rights reserved.