In Farenheit 451, What does the Salamander on Mantags arm and the Phoenix Disc on his chest represent?

First of all, the salamander is related to fire since there are ancient, almost mythological, beliefs that salamanders are unaffected by flames and could live in fire.  The phoenix also has its place in mythology:  it is a bird believed to have cyclically burned itself in flames, only to rise out of the ashes once again.  Literally, these symbols are both related to fire and creatures who were believed to survive fire, so it makes sense they'd find their way onto these fictional firemen uniforms.  Symbolically, they both, especially the phoenix, represent the idea of rebirth, which is what the resolution of "Fahrenheit 451" is all about - being able to rebuild.