Heating paper to a yellowish smoke

I put some papers into a biscuit tin and put it over fire and baked it. Then I made a small hole at the top and saw yellowish smoke coming out. Any idea what the smoke could be? 




What you've performed is, technically, "[thermal decomposition of cellulose](http://cdn.intechopen.com/pdfs-wm/45639.pdf)", or pyrolysis. During heating, there are large number of changes producing many different chemicals, so the smoke you saw was a [mixture](https://en.wikipedia.org/wiki/Mixture) of different chemicals. 


Pyrolysis is used to produce many industrial chemical, such as ["wood alcohol" (methanol)](https://en.wikipedia.org/wiki/Methanol#History), and during gasoline shortages, [to run internal combustion engines](http://www.lowtechmagazine.com/2010/01/wood-gas-cars.html).


[![Gasifier](https://i.stack.imgur.com/K2iSy.png)](https://i.stack.imgur.com/K2iSy.png)


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