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Far too often, industrial hygienists rely on direct reading instrument results without understanding all the calibration requirements, limitations, interferences, and errors potentially associated with a particular instrument. Discuss some of these factors affecting the results, and what steps an industrial hygienist should take to ensure the results they are obtaining are accurate and precise. Make sure your answer identifies an area of concern that has not yet been addressed, or provide a different point of view from your fellow students.
Expert Answer
For example different types of dusts can have particle size distributions that are substantially different from the calibration dust. This can lead to large deviations. An industrial hygienist will have to keep in mind that calibration is only valid for the specific calibration aerosol and can potentially differ by as much as ten times when it is used with an aerosol from a different aerosol size, different composition or a different source.
Thus industrial hygienists should have the knowledge about possible sources of error and they should be trained as well regarding the sources of error. For instance an industrial hygienist should be able to identify that at high humidity the chances of a false high reading will substantially increase because water droplets will be most likely detected by the photometer.
Errors can be minimized by verifying the instrument’s response to the aerosol of interest. Industrial hygienist will have to carry out serial gravimetric sampling in parallel with the monitor. This will help them in determining a correction factor (also known as calibration factor). The industrial hygienists can also use real time measurements to assess engineering controls. Industrial hygienists can also make use of data logging. The hygienists should keep in mind that the longer the data logging interval the less is the resolution that is provided by the tabular report.
