Information for round-robin test participants for in-house and external measuring stations

• Introduction
  It is the duty of the company to determine whether a concentration of hazardous substances is in the air at the workplace. The required measurements of the hazardous substances can be conducted by in-house or external measuring stations. A measuring station can be considered to be suitable if it has the necessary expert knowledge and the required facilities. The qualification is assured via an accreditation for measuring stations outside the company [1].
  
  No formal accreditation is provided for in-house measuring stations (IMS). Then the in-house measuring stations also have to fulfil the requirements for measuring stations according to TRGS 402 (Technical Regulation for Hazardous Substances) [2]. To maintain the quality parameters for analytic procedures, the quality assurance methods are to be used that are state-of-the-art. The Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA) provides round-robin tests as support and assistance for the IMSs. This should give the IMSs or an external laboratories working on their behalf an opportunity to document their own quality through external quality assurance procedures.
  
  All round-robin tests are being conducted in compliance with ISO-Guide 43 and with DIN ISO/IEC 17043 [3, 4].

• Organisation of the round-robin tests
  The production of the samples is done either at the IFA, or a suitable laboratory to be commissioned.

• Processing and documenting the analytic results
  At the end of every year, the schedules for the respective round-robin tests in the following year are announced. Once the samples are sent, the processing time is given - generally a period of around two or four weeks. This time frame may not be exceeded because results that arrive at IFA after the given deadline (date of postmark) are not considered in the evaluation.
  
  The samples include a USB-stick (1.1) for data collection.
  
  The results are collected with a special data entry program. The program runs on all Windows versions above Windows 2000. A hardcopy printout of the diskette is to be produced, signed, and sent to the IFA together with the diskette. Three analyses for each harmful substance are to be conducted from each sample. The individual results are to be filled into the data form.
  
  The complete statistical evaluation is carried out by the IFA. The data received are immediately made anonymous by the IFA. Then the analysis and a graphical presentation are prepared using the software Prolab Plus.
  
  The results will be evaluated using the z-score evaluation according to ISO Guide 43, Annex A [3].Upon completion of the evaluation, each participating measuring station receives a confirmation of participation with the following data:

  • Round-robin test name
  • Laboratory number
  • Own laboratory result and z-score
  • Set value of sample test tubes
  • "True value" of the samples after elimination of outliers (GRUBBS test)
  • Standard deviation
    
    as well as an round-robin test protocol with the following information:
    
    
  • Presentation of the total analytic results and deviations in tables and graphs
  • Presentation of the z-score evaluations in tables and graphs
  • Alphabetic list of all participants.
• Evaluation
  • General statistical parameters
  • Outlier test conforming to GRUBBS
  • z-score evaluation according to ISO Guide 43 [3]
    (see Information for participants)
    
    A result of |z| £ 2 is considered satisfactory, meaning that the round-robin test is considered "passed". If the z-score is above two, a test of the analytic method used is suggested.
• Certificate of attendance
  Participants receive a certificate, see specimen.