Proficiency testing of temperature and relative humidity in clean environments: evaluation of inspection and testing organizations in china

Objective: To design and implement a proficiency testing (PT) scheme for evaluating the competence of inspection agencies in measuring temperature and relative humidity (RH) in clean environments. The study assesses laboratories’ mastery of testing standards and their operational proficiency with thermohygrometers. Methods: The PT combined a written examination (evaluating theoretical knowledge of standards) and a field assessment (assessing instrument operation and field testing accuracy). Homogeneity of temperature and RH samples was verified using relative standard deviation (RSD). Participant performance was scored using weighted criteria: the written examination (40 points) and field test (z-score evaluation, 60 points). Results: Sample homogeneity met PT requirements. All 54 participating laboratories achieved satisfactory results (100% satisfaction rate). Field test z-scores indicated high consistency: 98.1% of temperature results (|z|≤ 2) and 94.4% of RH results (|z|≤ 2) fell within satisfactory ranges. Conclusion: Laboratories demonstrated robust testing capabilities, though improvements are recommended in standard interpretation and instrument calibration practices. This PT framework establishes a novel quality assessment method for pharmaceutical clean environments and serves as a reference for similar evaluations.