Hot/Cold smokehouse build

Look at the bottom of my post here, on my sig line is Smokehouse.  That's a link to my build.

I did wonder about fire retardancy, but heat rises, doesn't go sideways.  The walls of my smokehouse don't get uncomfortably hot at all and the majority of the heat goes out the top vent; and I keep it at 235° - 250° all the time for hot smoking.  Cold smoking I just use AMNPS, which has only a smoldering heat and burning pellets.  I did put flat 12"x12" blocks under the burner and stood 3 up to protect against flying sparks but have had no issues at all.   If I do another one, I will put blocks on the entire floor next time.  Sparks fly and land on the floor, not on the walls.