PRINCIPLES OF TOXICOLOGY

Figure 22.1
22.3 PROGRAM MANAGEMENT 535
Consider the example of an employee working 3 feet away from an open container of a solvent.
On questioning, the employee states that he uses 5 pints/day on Mondays and Fridays, but only 2
pints/day on the other days of the week. Clearly, if sampling were conducted on Tuesday, it cannot be
considered a “worst-case scenario.” Similarly, if the sample is collected directly over the top of the
container, it cannot be considered “realistic,” since the employee does not inhale the air directly over
the container. Thus, personal air samples should be collected on a Monday or Friday to document
compliance with government standards. However, suppose the container is equipped with a slot hood
exhaust system to prevent vapors from escaping into the workplace. Then we may wish to collect an
area air sample directly over the top of the container to determine the effectiveness of the control
system. In the latter case, we are measuring the degree of control present, not the employee’s exposure.
To this point we have described the choice of sampling strategy in terms of area versus personal
sampling, statistical considerations, and what a “representative” sample means. Sampling techniques,