I hate it when I have a good idea and then find out someone's already done a better version of the idea. This happened with my idea of taking a picture with an infared camera of a fire extinguisher discharging CO2, which I figured should basically look like a black plume.
Jeff S., a friend whose PhD in spectroscopy gives him a knowledge base nearing that of my own derived from watching nature documentaries, clarified that the idea required a heat source and that the CO2 be in between the heat source and the camera. Various details about camera operation and the frequencies it uses could also affect the outcome. But the principle should work, and I thought it could be an effective educational tool.
And then, Jeff found that BBC's already done it:
(If the embed doesn't work, you can watch it on Youtube.)
More info here, and a NOVA documentary apparently does something similar (I'll provide an update when I watch it).
What could still be useful is a photo instead of a video, not to mention one that's in the public domain so we could put it up on wikipedia.