I am looking to redo the fireplace in our 1905 home. The problem is this board inside the box. It is rigid but covered in a woolly white (well, it was white before it got a bunch of construction dust on it) material. I don't know what it is for or what it is made of and don't want to disturb it until I know. I'm assuming it was installed to keep cold air from coming down the chimney, but any idea on the material? If it's asbestos I want to make sure I have it disposed of properly, especially since I doubt I can remove it whole. I would like to remove it so I can examine the firebox and chimney before I decide how to proceed with the renovation/restoration.

You can see the gas burner in the front. I'm not sure if that is original or a later retrofit.

Close-up of the material.