In a fire scenario, huge amounts of heat are generated and high temperatures rapidly achieved in such a way that the integrity of structural materials becomes compromised. One of the aims of passive fire protection is the use of building materials that are able to absorb at least part of that heat and maintain the structural materials under critical temperatures for longer times in order to gain evacuation time. Gypsum panels are commonly used in building walls, but they only absorb heat at temperatures around 110 °C. We use three inorganic fillers, Mg(OH)2, Ca(OH)2 and CaCO3, which undergo endothermic transitions at high temperatures to obtain an improved panel with a richer heat-absorbing profile. With this formulation, the time to reach temperatures of the order of 500 °C, critical for steel and reinforced concrete, is significantly increased. In this work, we focus on the kinetics of the endothermic fillers as an essential ingredient for further spatially extended simulations that include macroscopic heat and mass transfer phenomena or sample heterogeneities. However, kinetics may be affected as well by heat transfer effects that occur at molecular levels. Copyright © 2014 John Wiley & Sons, Ltd.