Which term is a colorless, odorless, highly poisonous gas formed by incomplete combustion of carbon-containing materials?

• A. Carbon dioxide
• B. Decomposition
• C. Carbon monoxide
• D. Cast-off

Answer: (C)

Incomplete combustion of fuels produces a gas that is colorless, odorless, and highly poisonous. When a carbon-containing material doesn’t burn with enough oxygen, it doesn’t fully turn into carbon dioxide; instead carbon monoxide forms. The danger comes from carbon monoxide’s strong binding to hemoglobin in the blood, forming carboxyhemoglobin, which prevents oxygen from being carried to tissues. This can cause headaches, dizziness, confusion, weakness, and, at higher exposures, loss of consciousness or death. Because it has no smell or color, you can’t rely on senses to detect it, especially in enclosed spaces like garages or poorly ventilated furnaces—hence the emphasis on detectors and proper ventilation. By comparison, carbon dioxide is produced during combustion but isn’t the same acutely poisonous hazard at typical exposure levels; the other terms relate to processes or concepts not describing this combustion product.