Study of the performance of detector tube measurement systems

Status:

completed 05/2001

Aims:

Detector tube measurement systems may be employed for direct measurement of gases and vapours at workplaces, in addition to electrical measuring instruments. Detector tube measurement systems are classified as a "simple measurement procedure" and are recommended by the German Institutions for Statutory Accident Insurance and Prevention (GISBAU, health services). The effectiveness of such detector tube measurement systems is open to question, however. Are they suitable only for surveillance measurements, or do they also meet the more stringent requirements regarding measurement procedures employed for comparison with exposure limit values as defined in TRGS 402, which governs the measurement and assessment of the concentrations of hazardous substances in the atmosphere at workplaces, and in EN 482, "Workplace atmospheres: General requirements for the performance of procedures for the measurement of chemical agents"? The purpose of the studies was to establish the effectiveness of selected detector tube measurement systems. The results were to form the basis for information on the field of application. Recommendations were also to be provided for revision of EN 1231 "Workplace atmospheres - Short-term detector tube measurement systems".

Activities/Methods:

26 commercially distributed detector tube measurement systems were purchased from a number of manufacturers for the following substances: acetone, xylene, toluene, formaldehyde, carbon dioxide and carbon monoxide. The selection was based upon the incidence and relevance of the substances in exposure measurements, the need for measurement results to be suitable for direct evaluation, the availability of detector tube types from various manufacturers, and the availability of proven procedures for comparison measurements. Based upon EN 1231, defined test gases were employed to determine the measurement uncertainty of the detector tube measurement systems in the range of concentration between 0.1 and 2 times the exposure limit value, the distortion of the indication, the suitability for storage, the temperature resistance, the susceptibility to influence from vibration and shock impact and from the ambient factors of temperature and moisture, the suitability for re-use, the response to overloading, and the influence of interference components. The results were compared with the requirements of EN 482, "General requirements for the performance of procedures for the measurement of chemical agents", and of EN 1231.

Results:

Of the detector tube measurement systems studied, only a small number met the requirements of EN 482 concerning measurement procedures for comparison measurements with limit values. Suitable detector tubes were found for the following hazardous substances: acetone, xylene (with restrictions), toluene and carbon dioxide (with certain restrictions). For survey measurements, selected detector tube measurement systems were also found to be suitable for the following hazardous substances: xylene, toluene, carbon dioxide (with restrictions) and carbon monoxide. A large proportion of the detector tubes studied fulfilled neither the stricter nor the less strict requirements. Based upon the results of the study, recommendations were issued for the use of detector tube measurement systems. Comments were also issued concerning the revision of EN 1231.

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