"Halon" stems from my Navy days - I picked it up after firefighting training one day early on; Halon is a volatile fire extinguisher used commonly on ships (and in other industrial environments). The dispensing mechanism for Halon is such that it creates a vortex inside the compartment in which it is deployed, thereby removing nearly 100% of the oxygen in a matter of seconds, therefore extinguishing said fire. It is pretty wicked stuff.
'451' is the commonly accepted temperature at which auto-ignition of paper happens, although studies prove that this does vary.
There, now that I've bared my soul... I'm off to other things.