“Carbon dioxide is portrayed as harmful. But there isn’t even one study that can be produced that shows that carbon dioxide is a harmful gas.” -Rep. Michelle Bachmann, April, 2009
Carbon dioxide content in fresh air (averaged between sea-level and 10 kPa level, i.e., about 30 km altitude) varies between 0.036% (360 ppm) and 0.039% (390 ppm), depending on the location. Prolonged exposure to moderate[clarification needed] concentrations can cause acidosis and adverse effects on calcium phosphorus metabolism resulting in increased calcium deposits in soft tissue. Carbon dioxide is toxic to the heart and causes diminished contractile force.
Toxicity and its effects increase with the concentration of CO2, here given in volume percent of CO2 in the air: 1% can cause drowsiness with prolonged exposure. At 2% it is mildly narcotic and causes increased blood pressure and pulse rate, and causes reduced hearing. At about 5% it causes stimulation of the respiratory center, dizziness, confusion and difficulty in breathing accompanied by headache and shortness of breath. Panic attacks may also occur at this concentration. At about 8% it causes headache, sweating, dim vision, tremor and loss of consciousness after exposure for between five and ten minutes. Due to the health risks associated with carbon dioxide exposure, the U.S. Occupational Safety and Health Administration says that average exposure for healthy adults during an eight-hour work day should not exceed 5,000 ppm (0.5%). The maximum safe level for infants, children, the elderly and individuals with cardio-pulmonary health issues is significantly less.
