Indiana Fire Fighter Mandatory Practice Test 2025 – 400 Free Practice Questions to Pass the Exam

Hydrogen cyanide is a highly toxic compound that interferes with the body's ability to use oxygen at a cellular level. When inhaled or absorbed into the bloodstream, it binds to the cytochrome c oxidase enzyme in the mitochondria, which is crucial for cellular respiration. This binding prevents cells from utilizing oxygen effectively, resulting in a reduced capacity to carry oxygen in the blood. As a consequence, even if oxygen is present in sufficient amounts in the lungs, the cells cannot access it, leading to cellular hypoxia and potential organ failure. This underscores why the correct answer highlights hydrogen cyanide's specific impact on oxygen transport and utilization in the bloodstream.