Like any other polymer decomposition process, the products of PTFE decomposition depends on the chemical species present while PTFE is undergoing the process and temperatures.

**General process is this :** Decomposition  is  initiated  by  random-chain
scission, followed by depolymerization. Termination is by
disproportionation. And all of this happens rapidly above 600 K (~326 C). Hence, assuming cooking below 200 C, it would be completely safe. 

Oxygen usually does not enter the cycle directly but through water, to give species like, 

 - Carbonyl fluoride 
 - Carbonyl difluoride
 

as well as a host of fluorinated alkanes and alkenes like,

 - Hexafluoroethane 
 - Octafluorocyclobutane
 - Octafluoroisobutylene 
 - Perfluoroisobutylene 
 - Tetrafluoroethylene 
and more.

However, the chemicals (species) listen above are for controlled lab experiments. What happens in real like cooking scenario is not (or cannot) be anticipated. But, it can be readily said that the above species can react with other chemicals in food to five fluorinated compounds that **will be harmful** for humans. As a precaution, one should not cook above 200 C on PTFE coated utensils to be completely safe.

Check is extremely detailed page for abstracts from research papers on PTFE decomposition  [Fluoridealert.org][1]. 

[Polymer decompositions- check PTFE section.][2]


  [1]: http://fluoridealert.org/wp-content/pesticides/teflon.decomposition.prod.htm
  [2]: http://www.ewp.rpi.edu/hartford/~ernesto/F2012/EP/MaterialsforStudents/Patel/Beyler_Hirschler_SFPE_Handbook_3.pdf