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Smoke Pen

A smoke pen (or smoke pencil) is a device that emits a continuous stream of smoke for the purpose of visualizing air flow.  A smoke pen may be used during a blower door test to identify locations where air is leaking in or out of a building.  One type of smoke pen used for this purpose, such as Regin model S220, consists of a burning paraffin wick that extends adjustably from one end of a hand-held tube.  This tool is demonstrated as a way to find places where ducts are not fully sealed in YouTube video 1.  Alternatively, a stick of incense may be used.