Smoke tubes from companies such as Allegro, Draeger, Gastec, Kwik-Draw® (MSA), RAE and Verifit are an essential OHS tool. Beneficial uses of smoke tubes include respirator fit tests and air flow observations and measurements. Users of smoke tubes must be aware, however, of the significant risks if the tool is misused. Proper use of smoke tubes, therefore, is essential.
Smoke may be generated by a variety of chemical reagents. OSHA, however, specifies that only smoke generated by stannic chloride may be used for respirator fit tests. Most smoke tubes consist of a sealed glass tube containing stannic chloride. When the ends of the glass tube are opened (broken off) and moist air is drawn through the tube by attaching a rubber bulb to one end of the tube, white “smoke” comprised of stannic oxychloride and hydrogen chloride (HCL) is emitted out the other end with each squeeze of the bulb. High relative humidity generates the most smoke. The bulb may be squeezed several to many times to generate smoke before the stannic chloride is depleted.