A great and inexpensive way to monitor air movement in your fume hood or to test the laboratory ventilation system. Once ignited, these military-type smoke generators will allow you to safely determine if your room ventilation system operates properly or if your fume hood efficiently moves air. Smoke generators also enable you to trace air movement from the inside to the outside of a building. The white/gray smoke generated is a result of a chemical reaction, so there will be no messy residue in your lab or on your clothing. If your budget does not allow a velometer to check your fume hood, then at least consider using a smoke generator to be sure that your hood efficiently moves air. Two sizes of generators are available. The 30-second type will generate approximately 4,000 ft3 of smoke. This size should be adequate to test air movements within the laboratory or fume hood. The 3-minute generator will provide almost 40,000 ft3 of smoke. This generator would be your choice if you wish to trace the exhaust path from your hood or exhaust to a remote, outdoor roof stack. Sold in packages of two generators.