I have had several woodburning stoves over the years but none of them have been new and none came with operating instructions. Some of them have a device that can partially restrict the flow of smoke from the stove to the flue. I've always assumed that was meant to be used in conjunction with an air intake damper, to slow down the rate of burning eg. overnight. I've always been wary of restricting the flue in case it allows carbon monoxide or smoke into the room. I heard someone say these devices are actually fitted to prevent drafts when the stove is not in use. Is this correct?