Question 6 QMED02 - Electrician-Refrigerating Engineer

The Correct Answer is B. **Explanation for Option B (freeze burns and blistering):** Carbon dioxide $\left(\text{CO}_2\right)$ is stored under high pressure, often in liquid form. When released rapidly through a nozzle (as in a $\text{CO}_2$ extinguisher), it undergoes a sudden phase change (sublimation), expanding greatly and cooling dramatically. The temperature of the discharge cloud, which contains solid $\text{CO}_2$ particles (dry ice "snow"), is extremely cold, reaching approximately $-78.5^\circ \text{C}$ ($-109.3^\circ \text{F}$). Direct skin contact with the nozzle horn or the discharge stream can instantaneously cause severe cold-contact injuries, leading to freeze burns (or frostbite) and blistering, similar to thermal burns. **Why the other options are incorrect:** * **A) carbon monoxide poisoning:** $\text{CO}_2$ (carbon *di*oxide) is a different chemical compound from $\text{CO}$ (carbon *mono*xide). While $\text{CO}_2$ is an asphyxiant (displacing oxygen and causing suffocation), it does not transform into $\text{CO}$ and therefore does not cause carbon monoxide poisoning. $\text{CO}$ is typically a byproduct of incomplete combustion. * **C) undulation:** Undulation means a wave-like motion or variation. This term has no direct relevance to the chemical or physical dangers associated with $\text{CO}_2$ as a firefighting agent. * **D) hallucinations:** While exposure to high concentrations of $\text{CO}_2$ can cause dizziness, confusion, rapid breathing, and eventually unconsciousness (due to asphyxiation and hypercapnia), it is not typically known to be a direct cause of hallucinations in the context of firefighting exposure.