The psyker power Fiery Form has the psyker transform into warpfire as the old Dark Heresy power Molten Man (Disciples of the Dark Gods, page 29). This leads to some questions:

a) Is the psyker immune against fire-based attacks? If not, why not?

b) Is the psyker's equipment, both fire-proof, normally burnable or volatile (e.g. grenades) damaged in any way by his transformation?