I don't know what you want to use as the fire but I suggest getting Benge's animated decal (sprite) pack. Excellent. I use it in this example.
See image.
Hit trigger zone. Show decal and activate the rundecal.
;Artificial Intelligence Script
;Header
desc = Activate then Run Decal Loop
;Triggers
:state=0,activated=1:incalphafade=100,rundecal=2,loopsound=$0
; rundecal = 2-loop and face player
;End of Script
The decal needs to be invisible at start so here is the start code:
;Artificial Intelligence Script
;Header
desc = Instant On
;Triggers
:state=0:setalphafade=0,runfpidefault=1
;End of Script
This should get you started. Just add the hurt zone in the fire (I assume) There might be complications with that.
Hint: For timing use the "timerstart" in action part and "timergreater=x" in the conditions part then execute "decalphafade=0" and turn sound off. x is in milliseconds.