Question

why is carbon dioxide mostly found in deep wells, caves and mines?

Answer 1

Answer:

CO2 is the most infamous greenhouse gas. In caves CO2 is found in higher concentrations because it degasses from infiltrating waters or is produced by decomposing organic compounds

Answer 2

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why is carbon dioxide mostly found in deep wells, caves and mines?

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Carbon dioxide (CO2) is a colourless, odourless gas, normally present in the air we breath; "fresh air" has about 0.03% CO2 and about 21% oxygen (O2). (CO2 forms about 4% of the air we breath out - a low enough level for "mouth to mouth" resuscitation to work.)  In caves and old mines the concentration is normally up to about 1% but can be higher due to rotting vegetation or wood, organic pollution carried in by water, poor ventilation or heavy "caver traffic" in small passages.  Using a carbide lamp further depletes the oxygen level and adds to the CO2.  CO2 is heavier than air and may form pockets of higher concentration in low areas, particularly where these are badly ventilated.