vapor? who is claiming vapor? ACTUAL fuel went down the elevator shafts. JUST where do you think that much fuel is going to go?
If ALL the fuel from the plane didn't explode on impact, hypothetically, and entered just one floor of the WTC tower without igniting, and you were standing in it, it wouldn't reach up to the swoosh of your Nikes.
Now look at the reality of the fireball, and what was left, you tell us how much went down the elevator shafts (assuming the elevator doors were open on those floors). If kerosene DID breech the shafts, it would have to drip a quarter mile and then re-ignite on something and explode (if that's even possible -rather than just burn). Can you tell us what that could be? AND there happens to be film from the inside of the lobby of the North Tower after the impact. No smoke, no soot, nobody complaining about the smell of kerosene, just damage everywhere from an obvious explosion. No elevator doors blown off, but glass all blown out.
Pray much?