This paper examines the effect of additional heat input on the course of a moderately exothermic batchwise reaction (Delta T-ad= 60-150 K), carried out without cooling, for two upset conditions: 1. constant heating rate, e.g. an insulated vessel exposed to an external fire, an electric heating coil kept on, stirring (vigorous) without cooling; 2. heating with a medium of constant temperature, e.g. jacket heating operated with high pressure steam or thermal oil. The model reaction is the batchwise amination of p-chloro nitrobenzene in an industrial autoclave, according to: large excess GRAPHICS The desired reaction is of a rather low exothermicity, but the more exothermic decomposition of p-nitro aniline starts at temperatures not far above the usual maximum reaction temperature. The worst upset condition during the desired reaction is considered to be ＇leaving the steam heating on＇ in the adiabatic part of the process (175-198 degrees C) combined with ＇failure to blow off ammonia and water vapour above 200 degrees C＇. The effect of this upset condition is evaluated using the thermo-kinetic data of the reactions taking place. It is found that eventually a runaway will show up in the consecutive reaction, but this will take quite some time, sufficient to take counteractions. New analytical tools are developed to evaluate in general the effect of additional heat supply to an adiabatic batch reaction. For upset condition (1), a new definition of the final temperature, the temperature at which the conversion is almost complete, yields an equation for the range in which a reaction will occur. This range will considerably shift under the influence of variable imposed heating rates. The intriguing opposite is that in the limiting case without an imposed heating rate any reaction seems to occur between T= 0 K and T= Delta T-ad. Another analytical tool is estimating the course of the reaction temperature by simple algebraic equations. For upset condition (2), a dimensionless approach yields an expression for the conversion at the moment that the reaction temperature has become equal to the temperature of the heating medium.