The thermally safe operation of an indirectly cooled semibatch reactor in which an exothermic reaction occurs corresponds to conditions of potentially very high effective reaction rate compared to the dosing rate of the coreactant, whose accumulation in the reaction system is consequently small. On this basis it is possible to build boundary diagrams in terms of suitable dimensionless parameters, which summarize all the possible thermal behaviors of the reactor and can be used for safe scaleup purposes. In this work the influence of reaction kinetics on the shape and location of boundary diagrams for a single liquid-liquid reaction in the slow regime is discussed. First of all, the theory of boundary diagrams, originally developed for (1, 1) reaction order, is extended to a generic (n, m) rate of reaction expression. Then it is shown that in many practical systems, using boundary diagrams based on (1, 1) reaction order can lead to both unsafe and unnecessary (from a safety point of view) low-production operating conditions. New boundary diagrams for a few (n, rn) reaction orders are presented. Some rules-of-thumb are also discussed to identify in which cases a boundary diagram developed for a given (n, m) reaction order can be reasonably used to approximate the real kinetic behavior of the system of interest. Moreover, since building a boundary diagram for the specific kinetics considered can be necessary, a simple and general procedure for building such diagrams that can be easily implemented in a computer code is also presented. (c) 2005 Elsevier Ltd. All rights reserved.