Assignable analytical uncertainty can be considered as consisting of interlaboratory and intra-laboratory variability. Knowledge of the magnitude of these two sources of variability is essential in order to interpret and use analytical data property. Intralaboratory variability can be estimated from the results of analysis of blind samples, Inter laboratory testing requires the cooperation and coordination of a number of independent laboratories.

Inter laboratory testing can also be useful for defining the relationship of data reported by different laboratories using either the same or different measurement techniques.

Participation in such studies can be useful for uncovering errors in methodology or identifying critical steps in the procedures, The Proficiency Analytical Testing (PAT) Program operated by the American Industrial Hygiene Association (AIHA) in cooperation with NIOSH is useful for measuring a laboratory's performance on a variety of common occupational hygiene samples, including solvent vapours on charcoal tubes and metals, asbestos and silica on filters. Participation in this program by aboratories performing occupational hygiene analysis is strongly encouraged.

Similarly, the AIHA operates a laboratory accreditation program for occupational hygiene laboratories. Site visits and application reviews can provide a useful review of a laboratory 's overall quality assurance system, as well as the adequacy of personnel, facilities and equipment.