Question 64 CEL01 - Chief Engineer - Limited

The Correct Answer is C ### Why Option C ("phosgene gas") is correct Chlorinated fluorocarbon refrigerants (CFCs) and hydrochlorofluorocarbon refrigerants (HCFCs), such as R-22, contain chlorine atoms. When these substances are exposed to high heat (e.g., from an open flame, hot manifold, or glowing heating elements), they undergo thermal decomposition. This decomposition process releases highly toxic byproducts. A primary and extremely dangerous byproduct formed when chlorine-containing refrigerants are heated is phosgene ($\text{COCl}_2$). Phosgene is a colorless gas that was used as a chemical weapon during World War I and is highly toxic, causing severe respiratory damage (pulmonary edema) even at low concentrations. ### Why the other options are incorrect **A) carbon monoxide:** While carbon monoxide ($\text{CO}$) is a product of incomplete combustion of carbon-based materials, it is not the primary or most dangerous decomposition product specific to chlorinated fluorocarbon refrigerants when heated. The presence of chlorine in the refrigerant leads specifically to phosgene formation. **B) petroleum crystals:** This option is incorrect. Petroleum crystals are not a product of refrigerant thermal decomposition. Refrigerants break down into gases, not solid crystalline forms of petroleum. **D) water vapor:** This option is incorrect. Water vapor ($\text{H}_2\text{O}$) is a product of the combustion of hydrogen-containing fuels, but it is not a significant or toxic decomposition product unique to chlorinated fluorocarbon refrigerants. The decomposition products of concern are the highly toxic chlorinated compounds like phosgene and hydrogen chloride ($\text{HCl}$).