section_path: Biological role/Toxicity/Indoor air
section_name: Indoor air
paragraph_text: Indoor air
  
  Humans spend more and more time in a confined atmosphere (around 80-90% of the time in a building or vehicle). According to the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) and various actors in France, the CO rate in the indoor air of buildings (linked to human or animal occupancy and the presence of combustion installations), weighted by air renewal, is "usually between about 350 and 2,500 ppm".
  
  In homes, schools, nurseries and offices, there are no systematic relationships between the levels of CO and other pollutants, and indoor CO is statistically not a good predictor of pollutants linked to outdoor road (or air, etc.) traffic. CO is the parameter that changes the fastest (with hygrometry and oxygen levels when humans or animals are gathered in a closed or poorly ventilated room). In poor countries, many open hearths are sources of CO and CO emitted directly into the living environment.