ABSTRACTExperimental tests were carried on a pilot retort to gather information on the temperature evolution inside batch retorts during the venting stage. to fit the coming‐up curves the equation for the response of an over‐damped second‐order system to a step input was proposed. the parameters that characterize this equation were related to steam flow, initial temperature and retort load. Results allow the prediction of coming‐up curves for different operating con