The smoke-filled glass tubes are used in conjunction with the smoke test kit to indicate the proper fit of a respirator, and to determine the adequacy of the air flow in a given work environment. With a break-off tip, you can easily discard the tube after the test. To avoid false alarms, it is recommended that a detector be placed at least 20 feet away from the tube. It is intended for use with standard smoke test kits. There are (6) smoke tubes in a pack.