The Heavy Duty Smoke Pencil Pro is the tool Professional Energy Raters and Contractors use to identify drafts and air leaks in a home. This non-toxic smoke stick generates a small trail or large puff of smoke to help you identify drafts. Pull the trigger on the Smoke Pencil Pro near the area that you suspect a draft and see how the smoke moves to show air current or leakage. The light on the top of the Smoke Pencil Pro illuminates the area you are testing for easy air movement detection. A 3oz smoke fluid bottle (with a special filling tube) is included with the Smoke Pencil Pro. 6 - AA batteries not included.You control the amount of smoke this Smoke Pencil generates by holding the finger trigger. The smoke is a harmless non-toxic sweet smelling Water, Glycol and Glycerin mixture (similar to toy train smoke) vapor. It does not use the dangerous and caustic acid or incineration based smoke that other smoke sticks often produce.