REGIN smoke cartridges are an economical and practical method of generating a realistic swirling, non-toxic smoke with a particle size of .3-2.5 microns. The smoke contains no zinc or oil and leaves behind no residue. This premium product is the best tool for testing, duct systems, providing a visual display of air-flow, for balancing or leak detection in; exhaust air systems, smoke stacks, chimneys, fume hoods. Ideal for negative air pressure testing, smoke alarms, fire drills, film and photography, verification of high efficiency air filter operation, and virtually hundreds of other applications. With increasing emphasis on environmental and safety issues, this is an invaluable, practical and economical tool. REGIN Smoke Cartridges are extremely stable and have a long shelf life of up to 3 years.