The article deals with the estimation of negative influence (impact), provided by dangerous factors, appearing during fire hazardous situation. It is clear, that both thermal stream and inner overpressure mutually can lead to the machine depressurization and destruction, which can cause cascading troubles, making situation more hurtful, than it was. The application of mathematic model is suggested in order to estimate the probability of equipment backstop integrity, which guarantees the evaluation of prevention possibility of the Domino effect.