I just meant to fluff it as the same as his force field, there would have to be a different game mechanic that would do the heavy lifting.
Basically, in some way he bends space around the bad guy so that the fire can't go beyond a foot or two, folding the space back in on himself. He probably is immune to his own power, but at least the fire wouldn't be able to go any further, giving us a chance to get the people out.
I suppose "Create" would work, but it gives him a Dodge save. Is he in the midst of them, or is he on one side and the hostages on the other? Cause I could just make a wall between them.
Or I could do a fly over and turn off the gravity in that room. Makes it so everyone floats. Don't know how that would helps, but it's something I can do.