On his fantastic blog: Things I won’t work with, Derek Lowe points out a couple of fearsome oxidisers. I am pretty certain that they will react with carbondioxide. The lesser of the two will set quartz sand on fire. (Sand won’t save you this time. Worth a read.) And this link shows the culpritChlorine Triflouride and a video of some French chemists demonstrating how it renders all their safety equipment useless.
This all pales in comparison toFOOF.
Short answer to the flammability of CO or CO2 even. With the right oxidiser, pretty much anything will burn.
Since fluorine is more electronegative than oxygen, you can get all kinds of nasty reactions between fluorine compounds and materials we normally consider inert. Like sand.
To me it had no humorous value, but I considered it so likely to be a joke instead of ignorance that I posted a paraplegic joke in return instead of a lesson on the equality between flammable and inflammable. You see, unflammable isn’t even a word, cromulent though it may appear.