2 hour rating of an open-web steel joist and concrete floor system

I have an existing open web joist framed floor system with a 3 1/2 thick concrete floor slab over metal lath and need a 2 hour floor system rating. We initially specified a gypsum ceiling but there's too much material and equipment in the area. Looking for an applied intumescent solution. The joists are 12” deep with the top and bottom cords (2 each) @ 5/8” diam. With the center web bars ½” diameter.