The methods of light microscopy, immunohistochemistry, and electron microscopy were employed to study the morphofunctional changes in epithelium of bronchial and respiratory segments of the rat lungs used as models of acute fatal poisoning with household gas. It was shown that this toxic effect induces the pathological process involving all the elements of the epithelial layer in the bronchial and respiratory segments of the lungs of experimental animals. At the ultrastructural level, mitochondria and endoplasmic reticulum structures are affected, with the death of epithelial cells leading to the damage of the aerohematic barrier. The toxic effect of the gaseous mixture on the membranes causes the destruction of various elements of the epithelial layer. The results of this study help to understand the mechanisms of death in the case of acute fatal poisoning with household gas.