Smoke sticks provide an inexpensive method of generating swirling smoke. This is a great product for testing air direction and velocity on ventilation inlets. Can also be used when checking for leaks around curtains, doors and fans openings. The smoke emitted does not contain oil or zinc and will not leave any residue. It is non-toxic and has the same density as air, so that it is possible to observe true air movements. The smoke has a particle size of 3-2.5 mitcrons. The smoke cartiridges produce a generous amount of smoke, which is emitted at a constant rate to help with the identification of flow patterns. Smoke color is white and they are packaged 10 per box.