Technician Team Exam - BioPak 240 From the 2013 Nevada Mine Rescue Contest, Winnemucca, NV Progress Indicator: Question 2 of 30 2.  Smoke tubes are useful to do which of the following? Choices: Finding velocity of slow moving (<120 ft/min) air Show direction of air movement Fit testing BG-4 breathing apparatuses A and B All of the above