*throws hands up in exasperation* I feel like such a newbie it's not even funny At least even though my hubby grew up woodburning in a fireplace, thanks to these forums I do actually know more about burning in a stove now than he does ...maybeMore likely it is to slow down draft a bit to keep the firebox hotter for a cleaner burn to meet EPA requirements. Maybe contact [email protected] with Morso specific technical questions?