No more heat loss or draughts down your chimney the quick and easy way to prevent draughts and up draughts this chimney balloon will also stop soot and bird droppings messing up your hearth simply inflate to block your chimney cavity and deflate to remove when you want to start a fire the shape of the balloon allows a little ventilation to prevent rooms getting stuffy and polluted to choose correct size measure your chimney inside about a foot or so up from side to side and from front