ABSTRACT
OBJECTIVE: To evaluate the major influence factors affecting the quality and accuracy of measuring instruments for power frequency electromagnetic fields in occupational hygiene technical service organizations by developing interlaboratory comparison in workplaces. METHODS: Six measuring instruments for power electromagnetic fields from 6occupational hygiene technical service organizations in Guangdong Province were selected by typical sampling method. A high-voltage substation was selected as a standard source. We set measurement sites underneath it as inter-laboratory comparison spots for power frequency electromagnetic fields. The stability of the standard source was evaluated by pairedsamples t-test and measure results were analyzed by z-score evaluation method based on quartile robust statistical technology. RESULTS: During and after the inter-laboratory comparison,the intensity of electric field and magnetic field of the standard source showed no significant difference [( 555. 03 ± 2. 94) vs( 555. 68 ± 3. 20) V / m,( 2. 30 ± 0. 06) vs( 2. 29 ± 0. 07) μT,P > 0. 05],which met the demand of stability of inter-laboratory comparison. The data of electric field measured by 2 measuring instruments without remote-reading system were found to be high because of proximity effect from its handheld status. The z-score of inter-laboratory( zB) of other 4 measuring instruments with remote-reading system ranged from- 0. 52 to 1. 10,while the z-score of within-laboratory( zW) ranged from- 1. 28 to 0. 37,and both results of| zB| and | zW| were satisfactory( < 2. 00). The zBof power frequency magnetic field measured by the 6 measuring instruments ranged from- 0. 67 to 1. 26,while zWranged from- 0. 59 to 0. 90,and both | zB| and | zW| were also satisfactory( < 2. 00). CONCLUSION: It is feasible that the inter-laboratory comparison of measuring instruments of power frequency electromagnetic fields could be implemented by a high-voltage substation as a standard source. The measuring instruments without remote-reading system could be used to measure the intensity of magnetic field but not the electric field. The measuring instruments with remote-reading system could be used to measure the intensity of either the electric field or the magnetic field,and the measurement results are satisfactory.