Hazards of Process Sampling

Upon completion of this chapter the student should be able to  

This is a short chapter that briefly introduces you to the environmental, safety, and health hazards associated with the collection of samples, their transport, and ambient air sampling instrumentation (gas detectors). Process technicians and analyzer technicians will frequently be involved with collecting samples. 

You might wonder, what is the big concern about catching a sample to warrant a whole chapter If you work in the refining or petrochemical industry, your sample might contain components that might contain all the following hazards  

Over the course of a year, some process technicians may collect hundreds or even thousands of samples. Over a 20- or 30-year career, a technician may collect tens of thousands of samples. Each sample collected, due to its chemical nature, may pose a health or physical hazard. Sample collection must always be done with care to avoid possible injury or health effects to the sample collector. 

Besides collecting samples for process control reasons, process and analyzer technicians also use certain instrumentation to sample the air quality in certain areas, vessels, or during unit turnarounds. The instruments they use (gas detector) informs them of  

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The reduction or elimination of contamination hazards of the sample during processing unless the laboratory is contaminated by radionuclides. 

The evaluation of hazards posed to human health by toxic airborne chemicals is one of the common tasks employed in industrial hygiene. This process requires the collection of air samples to estimate air concentrations of specific substances inhaled by workers which can then be compared with standards and guides of acceptable exposure. Thus air sampling directly influences the formulation of important decisions. If air samples underestimate exposures, the consequence may be death or occupational disease. Conversely, overestimating exposures may result in the institution of unnecessary controls. Since either form of error is undesirable, it is fundamentally important that air sampling accurately define the extent of hazard. This requires that air samples be collected according to scientific, unbiased schemes for estimating exposures to toxic airborne chemicals. 

Reduction in the number of chemical processing steps allows for significant reduchon in the amount of in-process and Quality Control (QC) analysis of raw materials and intermediates required in the semi-synthetic route. Reduced handling and storage/disposal of cytotoxic samples by operators and analysts reduces opportunities for hazardous exposure. 

Tests on mixtures must be run at a temperature at which the sample is completely vaporized. If the vapor pressures of the components are widely different, results can be unreliable, and often cannot be related to the hazards under process conditions. 

The scope and limitations of the use of DSC as a means of investigating the reaction dynamics of potentially hazardous chemical reactions is discussed. For existing processes, examination of production samples taken at various stages of the overall process sequence can identify the stage at which maximum heat production is occurring, as the most critical phase for control requirements. The existence of an induction period can also be established, and use of the instrument in its more sensitive isothermal mode can yield information on consecutive reactions and catalytic effects... 

Because small amounts of radium radionuclides in environmental samples may be regarded as hazardous, it is usually necessary to detect very small quantities of radium which may require processing large quantities of sample (Quinby-Hunt et al. 1986). This introduces possibilities for contamination and sample loss. Specifically, in the case of water samples, sorption of the radionuclide to container walls and to suspended matter may be important sources of error. 

The second point is to always run tests on representative samples. Table IV illustrates this point. Original thermal stability tests were run on an alpha-oximino ester intermediate product that had been isolated by adding water to the reaction mixture, extracting the oil layer that forms with methylene chloride, and removing the methylene chloride by vacuum distillation (labelled pure oil). Later in process development it was decided to eliminate the methylene chloride extraction and separate the oil from the water layer (labelled crude oil) If repeat safety tests had not been run, the thermal stability hazard of this compound might never have been realized, and the compound might have been improperly stored or handled at too high a temperature. 

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