Question

Carbon monoxide, a substance found in tobacco smoke, is also found in __________.

Answer 1

Carbon monoxide is also a primary toxin found in many types of vehicle/machine exhausts.
Hope that helped =)

Answer 2

Answer and Explanation:

Carbon monoxide is a toxic, odorless, colorless and tasteless gas, partially soluble in water, alcohol and benzene, it's the result of incomplete oxidation of carbon during the combustion process.

It is the most abundant and widely distributed air pollutant of those found in the lower layer of the atmosphere, called the troposphere.  Its main natural origin is the oxidation of CH4 and, since all the methane in the atmosphere is produced by anaerobic decomposition of organic matter, it can be said that these processes constitute a natural source of CO.

The oceans constitute the second major source of atmospheric CO. Since surface waters are in contact with the atmosphere, it should be expected to contain in CO solution absorbed by it. Also because of the car is the most important isolated source of CO (around 65.6%), very populated urban areas show the highest environmental concentrations of this gas.