is a product of incomplete combustion. It is dangerous to humans and animals, as it sets in blood hemoglobin, preventing oxygen transport in the body. Furthermore, it is odorless, and time to feel a slight headache, it's too late. Josyann Abisaab It easily dissolves in the ambient air, but in a closed environment, their concentration makes it very toxic, even deadly. Each year, there are multiple cases of fatal poisoning due to combustion devices put to work in a stuffy room. Internal combustion engines of cars emit carbon monoxide into the atmosphere so that in highly urbanized areas tend to have an excessive concentration of this gas to reach concentrations of 50-100 ppm , rates that are dangerous to health of people.