All of the above, because not only does the suit need to be fire safe but it also has to be comfortable for the fireman to perform their very best. They would have to consider how each material might carry and hold smoke and withstand fires so that the materials not only block the fireman from getting burnt, but also prevent them from getting too overheated because you don’t want to make the suits too thick to the point that the fire mixed with the suit will make them too exhausted or heavy. When there’s an immediate emergency, you need to consider which materials might be lighter because it’s hard to move quick with heavy uniforms
