Analytical data are used to make a variety of decisions, e.g. to decide whether a particular chemical agent is present in a workplace atmosphere, whether a hazard to workers health exists in that atmosphere, or whether a workroom atmosphere complies with applicable standards. Errors in such data can have a variety of costly effects. The consequences of erroneous data may lead to the wrong decision being made as to whether a non-compliance situation exists. If the analytical results are a part of a larger experiment, perhaps the wrong conclusion might be reached or the results might be uninterpretable. If the presence or absence of a particular agent is erroneously reported, a threat to workers' health may be allowed to continue. It is the role of a weighing facility's quality assurance program to provide the necessary safeguards to minimize these occurrences and to provide a means of detecting errors when they do occur.

It is not possible to design a quality assurance program to fit all weighing facilities since no two weighing facilities serve the exact same purpose or operate in exactly the same manner. Each weighing facility must set its own operating procedures and quality control practices, and document them in a Quality Assurance Manual. This chapter, therefore, will not set forth concrete recommendations for implementing a quality assurance program, but rather will present aspects of weighing facility quality assurance and quality control, which should be addressed by each facility.

A successful quality assurance effort cannot be achieved through the efforts of only one individual. A weighing facility's quality assurance coordinator needs the assistance and cooperation of all facility personnel to be effective. To this end, it is necessary to discourage adversarial relationships between quality control personnel and bench chemists. Analysts must be trained and made aware of the purpose and value of quality assurance functions and, in turn, the quality assurance program must be designed so that its functions are based on sound goals directed toward improving the performance of both the individual analyst and the facility as a whole.

Frequently, analytical results are challenged months or years after the analysis is complete. In order to support the original data, an effective record-keeping system must be maintained. Another chemist must be able to reconstruct the exact treatment to which the samples were subjected solely from an analytical laboratory's records. Furthermore, if the appropriate quality control checks were performed with the analysis and documented, there can be no doubt regarding the results.