What is the composition in our Town Gas?

Natural gas is made up mainly of methane, which is composed of carbon and hydrogen. It burns more cleanly than other fossil fuels, producing fewer emissions of carbon dioxide (CO2), nitrogen oxides (NOx) and sulphur oxides (SOx). When natural gas is released into the atmosphere, it dissipates rapidly as it is lighter than air.
http://www.hkcg.com/naturalgas/eng/WhatisNG.html
天然氣是一種碳氫化合物，主要成份為甲烷。燃燒天然氣時，二氧化碳 (CO2) 、氮氧化物 (NOx) ，以及氧化硫 (SOx) 的排放量甚低，比其他化石燃料更為潔淨；天然氣較空氣輕，一旦排放到空氣當中，便會迅速擴散。
http://www.hkcg.com/naturalgas/chi/WhatisNG.html
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2006-12-16 18:49:13 補充：
Town Gas includes 49.0% of Hydrogen (H2), 28.5% of Methane (CH4), 19.5% of Carbon dioxide (CO2), and 3.0% of Carbon monoxide. An odourant is added to town gas for us to detect gas leakage since town gas is flammable and poisonous. (http://hk.knowledge.yahoo.com/question/?qid=7006033101213)

H
CO
CO2
CH2