It is an invisible, odorless, colorless gas created when fossil fuels such as gasoline, wood, coal, propane, oil and methane burn incompletely. Home heating and cooking appliances are possible sources. A vehicle running in an attached garage is another source.
Carbon monoxide replaces oxygen in the bloodstream, a condition known as carboxyhemoglobin.
No adverse effect within 8 hours 200 Mild headache after 2-3 hours of exposure. 1000 Loss of consciousness after 1 hour. 30-40 Severe headache, weariness, dizzy, weak sight, nausea, vomiting, prostration. 60-70 Possible death. 70-80 Death within hours.