As I understand it, fire requires fuel, oxygen, and heat (or an ignition source). My guess is that the patterns of flame appearing in the jar have to do with the movements of air (which contains about 21% oxygen) into and out of the jar's limited opening.

Also, while we do exhale CO2, a normal inhalation/exhalation cycle does not nearly use up all of the oxygen in that air. It still contains approximately 15% oxygen, which is why CPR works. So if they had used up all of the oxygen in the jar, a breath into it would reintroduce oxygen much more quickly than a normal air current would.

I don't think it's about (re)introducing oxygen into the system, but stirring up the fuel/air mixture. If most of the vapors are sitting at the bottom of the jug or don't quite reach the top you're going to have a hard time igniting.

The flame at the top should be burning oxygen from the surrounding air, while getting fuel vapors from the jug which are being pushed up by the heat of the bottom flame sheet (if the mix was too rich in the jug the existing oxygen wouldn't be enough to burn all the fuel). So like a candle with an air wick.

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Adding video to channels (Timeshift) - requested by ant.

You can do the same thing with rubbing alcohol and a 2 liter bottle... Pour a little alcohol in, cap it, shake it up, lighter at the opening and it does pretty much identical blue jet effect. Once it goes out if you blow some air in and shake it up again it can be done again and again until there's more water left in the bottle than alcohol so it's best to get the more concentrated bottle of alcohol (70% is the usual kind).

Loads of barely dangerous fun. =)

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