How does carbon monoxide (CO) in smoke affect occupants' ability to exit?

• A. CO reduces oxygen delivery, causing headache, dizziness, confusion, and incapacitation, hindering evacuation.
• B. CO improves visibility.
• C. CO neutralizes heat.
• D. CO has no effect.

Answer: (B)

Carbon monoxide in smoke hinders exit by binding to hemoglobin far more readily than oxygen, forming carboxyhemoglobin and reducing the blood’s ability to carry oxygen to the brain and muscles. That drop in oxygen delivery produces symptoms like headache, dizziness, confusion, and fatigue, and can progress to fainting or outright incapacitation. When someone is incapacitated, it becomes much harder to think clearly, move quickly, or find and reach an exit. CO is colorless and odorless, so people may not notice exposure until symptoms appear, which can complicate evacuation further. Visibility in a smoke-filled environment is largely reduced by the smoke itself, not by CO, so CO does not improve the ability to see. The main danger is the impairment of function from reduced oxygen delivery, which directly hinders evacuation efforts.