Abstract
The purpose of this research is to establish a method for measuring airborne asbestos concentration that can obtain an analysis value with the accuracy required for administrative guidance quickly at an analytical instrument owned by a local government.
The time required to count a sample was measured using phase contrast microscopy and scanning electron microscopy. We compared about the eight types of measurement methods described in the asbestos monitoring manual from the results of verification experiments and literature surveys. The comparison items were the state of ownership of measuring machines in local governments, portability to dismantling sites, measuring conditions, analysis accuracy,purchase price of measuring machines, the analytical advantages and issues. As a result, it was judged that simplification of the phase contrast microscopy method with maintaining the analysis accuracy was most effective.
We verified the time required for measurement, analysis accuracy (the lower limit of detection, the error range of the measured value) when the sampling time and the number of counting fields of view were changed in phase contrast microscopy.
The asbestos monitoring manual describes conditions (sampling 30 minutes and the counting 100 fields of view) for when particularly quickness is required, and the calculated measurement time was 2.2 to 4.7 hours, the lower detection limit was 0.4 fiber / L, and the error range of measurement value was 1.6 fiber / L. As a result of comparing the measurement conditions, when the sampling time was 2 hours and the counting 50 fields of view, the measurement required time was 2.8 to 4.1 hours. And when the sampling time was 1 hour and the counting 100 fields of view, the measurement required time was 2.7 to 5.2 hours. Under both measurement conditions, the lower limit of detection was 0.2 fiber / L, and the error range of the measured value was 1 fiber / L.
These two measurement conditions were almost the same in measurement time and higher in analysis accuracy,compared to the measurement conditions especially when rapidity was required. It is considered that these two measurement conditions can be used when promptness is required in on-site inspection at the time of asbestos-containing building demolition and renovation works.
