Question: We're replacing the stone on an old fireplace and we're not sure if we need to maintain the 4 existing vents in each corner. There are no fans, just vents. Now that we have some of the old stone off, we can see the metal surrounding the fire box and there are tunnels running from (or to) the top vents alongside the inside metal. It appears the bottom vents have no such tunnels. Finally to the question, do we need to maintain the vents or can we have the stonemason close them in? We have never noticed whether or not heat escaped from these vents when the fire was lit. Answer: These vents are usually required in order for the fireplace to cool itself. Do not cover them over.