Even three or four hours after exposure, half the excess carbon monoxide may remain in the blood stream. Those with respiratory or heart illnesses. Those with anemia. Tests of automobile drivers show exposure to high levels of carbon monoxide can impair a driver's judgment and ability to respond rapidly in traffic. At concentrations commonly monitored in the ambient air, carbon monoxide does not appear to adversely affect plants, wildlife, or materials.
Carbon monoxide is a common indoor air contaminant.