Calculations using the example of a reinforced concrete ribbed slab have shown that if, as a result of an explosion, due to cracks that have arisen, a part of the compressed concrete layer is turned off, then even while maintaining the bearing capacity of the slab, its fire resistance is significantly reduced. It is shown that on the basis of the proposed methodology for studying the behavior of bending elements under the combined effect of "explosion-fire", it is possible to take into account the necessary parameters of reinforced concrete ribbed slabs in the design and operation of structures of hazardous operations industrial facilities. Also, the proposed technique makes it possible to predict a relatively safe amount of explosive in the technological process of an hazardous operations industrial facility, without leading to catastrophic consequences.