How much carbon dioxide would kill you?

CO2 is toxic in higher concentrations: 1% (10,000 ppm) will make some people feel drowsy.

  • If exposed at a level of 2% for several hours, minimal "acidosis" (the acid condition of the blood) may occur (cf. hyperventillation prevention).
  • Breathing rate doubles at 3% CO2 and is four times the normal rate at 5% CO2.
  • Toxic levels of carbon dioxide: at levels above 5%, concentration CO2 is directly toxic. [At lower levels we may be seeing effects of a reduction in the relative amount of oxygen rather than direct toxicity of CO2.]
  • Symptoms of high or prolonged exposure to carbon dioxide include headache, increased heart rate, dizziness, fatigue, rapid breathing, visual and hearing dysfunctions.
  • Exposure to higher levels may cause unconsciousness or death within minutes of exposure.
  • Concentrations of 7% to 10% cause dizziness, headache, visual and hearing dysfunction, and unconsciousness within a few minutes to an hour.