1. Detector Tubes

2. Detector Tubes Pros Specific to selected chemical Cons
Cheaper than chemical specific monitor
Lightweight
Ease of use
Cons
Often inaccurate
Impractical in some situations
Special storage considerations

3. Detector Tubes
Toxic atmosphere monitoring with detector tubes can be done to:
identify airborne concentrations that could pose a toxic risk to response workers and the public.
evaluate the need for and type of personal protective equipment.
set up work zones or areas where contaminants are or are not present

4. Detector Tubes Principle of Operation:
Colorimetric indicator tubes consist of a glass tube impregnated with an indicating chemical.
Sample is drawn through the tube with calibrated hand pump or bellows.
Tubes then change color in proportion to chemical concentration in the air.

5. Detector Tubes
Some testing of detector tubes certified the accuracy to be +35% at concentrations at 1/2 the OSHA Permissible Exposure Limit (PEL) and +25% at 1 to 5 times the PEL.
NIOSH has discontinued testing and certification. Special studies have reported error factors of 50% and higher for some tubes.

6. Detector Tubes
The response time, sensitivity, selectivity, accuracy and precision of an instrument are important in evaluating the reliability and usefulness of the data the instrument generates.
Caution must be utilized with detector tubes, as they lack several of these criteria.

7. Detector Tubes
Tubes are assigned a shelf life. This varies from 1 to 3 years.
An advantage that Detector Tubes have over some other instruments is that it is possible to select a tube that is specific to a chemical.
Interpretation of results can be a problem, since the tube's length of color change indicates the contaminant concentration(color blindness, poor visibility conditions).

8. Detector Tubes
It may take 1 to 2 minutes for each volume (stroke) to be completely drawn. Therefore, sampling times can vary from 1 to 30 minutes per tube.

9. Detector Tubes
It is very important to read the instructions that are provided with and are specific to a set of tubes. The information includes the number of pump strokes needed, time for each pump stroke, interfering gases and vapors, effects of humidity and temperature, shelf life, proper color change and whether the tube is reusable.

10. Bibliography
DiNardi Salvatore R. (1998) The Occupational Environment-Its Evaluation and Control, AIHA, Fairfax, Virginia
Goetsch David L. (1999) Occupational Safety and Health for Technologists, Engineers, and Managers, Prentice Hall, Upper Saddle River, New Jersey