Fire caused by spontaneous ignition represents a serious danger for working and living environment. The process of tobacco's self ignition is slow but it drives to the ignition of tobacco that is hard to extinguish, and it drives to loss and other harmful consequences. That is the reason to conduct research on the causes and mechanisms of this phenomenon. The results obtained depend on the methods and applied equipment. This paper describes the procedure to specify specimen temperature versus ambient temperature on the time basis. The equipment applied as well as the measuring process are described in the paper. We have concluded that the values of self ignition temperature are not laboratory constants for certain species of tobacco, but variables which first of all depend on the temperature of the working environment. Data that we got in the experiment may be used to train RBF (Radial Basis Function) network. After training, RBF network was able to predict self ignition temperature for some cases of working environment temperatures that are not usually considered.