When natural gas and air are used to make CO2 for recarbonation, good ventilation is required because dangerous concentrations of which gas are produced?

• A. Hydrogen sulfide
• B. Formaldehyde
• C. Carbon monoxide
• D. Methane

Answer: (C)

When fuels are burned with air, incomplete combustion can form carbon monoxide. Natural gas is mainly methane, and while complete combustion yields carbon dioxide and water, insufficient oxygen or poor mixing can produce carbon monoxide, a colorless, odorless, highly toxic gas that binds to hemoglobin and prevents the blood from carrying oxygen. In a setup where natural gas and air are used to generate CO2 for recarbonation, any buildup of carbon monoxide in poorly ventilated spaces can reach dangerous levels, so good ventilation is essential. The other gases mentioned may be present in some contexts, but they are not the immediate hazard produced in this combustion process.