Apart from dust and batteries, are there really a lot of flammable things in equipment bays? Most things in there should either be either heat or flame resistant. No wood, paper, fabric, etc.
Metal racks, metal boxes, fire-retardant insulation blankets, hopefully non-Kapton wiring, a few small plastic items, ....
Of course, then there are the oxygen bottles on some aircraft types, but hopefully the O2 will vent overboard if the heat causes the O2 pressure to rise.