Chimney Balloon Inflatable, reusable plastic balloon, designed to stop chimney draughts, reduce outside noise and reduce heat loss. It works in two ways: stopping cold draughts coming down your chimney and stopping warm air escaping up your chimney. The heat sealed plastic inner sleeve stops leaks. The chimney balloon is curved at one end to allow for a little ventilation to prevent build up of condensation. Supplied as a boxed product.