The harmful compound is Methane with the chemical formula
CH4. It is made up of the elements carbon and hydrogen.
Carbon and hydrogen elements are not harmful individually, but when chemically combined, methane, a greenhouse gas, is formed. Methane can cause suffocation when its concentration in the air is too high and it can also lead to combustion when its concentration is around 5 to 15 percent, in contact with oxygen. It is thus considered a dangerous compound.
Please refer below for the dot-and-cross diagram.
Sources
Introduction:
http://en.wikipedia.org/wiki/Methane
Information on effects:
http://www.ehow.com/about_5106705_methane-harmful.html
Natural Gas:
http://www.naturalgas.org/overview/background.asp
