Actually quite real.
Nitrogen supercools tarmac.
Oxygen condenses on tarmac, soaks in.
Tarmac goes boom as it warms up, or a fly lands on it.


Interesting, although I don't recall any warnings about this in all my years of
working with cryogenics, though. LN2 isn't all that much colder than the
condensation temperature of oxygen (-270 F) but if the tarmac got to full LN2
temp (-320 F) it could work. Certainly LN2 doesn't cause oxygen to condense
appreciably in typical lab conditions.

Now, chilling from liquid hydrogen definitely does it. On un-insulated flex
lines, the LH2 (at -420 F) would condense oxygen and nitrogen directly out of
the air, and it would actually 'rain' in the vicinity of the LH2 lines. The LN2
tended to gas off fairly quickly, leaving it LOX enriched. If the droplets of
liquid air hit grease, you got little *poofs* as they ignited.

Note, temperatures are from memory, I don't have a chart handy.

DT