Carbon monoxide concentrations as low as which value can cause headaches, nausea, and dizziness after 45 minutes of exposure?

• A. 50 ppm
• B. 400 ppm
• C. 800 ppm
• D. 1200 ppm

Answer: (C)

Carbon monoxide harms by binding to hemoglobin almost 200 times more readily than oxygen, so it quickly reduces the blood’s oxygen delivery to tissues. The symptoms you get depend on both how high the concentration is and how long you’re exposed. At around 800 ppm, enough CO can saturate hemoglobin within about 45 minutes to produce headaches, nausea, and dizziness. Lower concentrations take longer to cause similar symptoms, while much higher concentrations produce them more quickly and with greater severity. Because CO is colorless and odorless, people can be exposed without realizing it, which is why understanding these thresholds matters.