[Procedures] Article 641 The monitoring of dust should adopt fixed-point monitoring and individual monitoring methods.
[Execution Description] The individual monitoring method refers to a method of continuously extracting dusty air in the breathing zone by using a dust sample individual sampler worn on the worker to measure the average dust concentration contacted by the worker in a work shift. The measured results have practical significance for understanding the dust concentration actually encountered by the workers every day and for evaluating the harm of the dust to the health of the workers.
The particle size of the individual sampler used in China's coal industry should be in accordance with the BMRC curve, that is, the maximum aerodynamic diameter of the classified dust particles is 7.07μm, and the deposition efficiency is 0. 50% of the dust particles at the deposition point is 5.0 μm.
Individual sampling is a one-time continuous sampling on a full working day. The 8h time-weighted average concentration of dust in the air is calculated as follows:
TWA in the formula - 8h time-weighted average concentration of dust in air, mg/m3;
M2——the quality of the filtered membrane after sampling, mg;
M1——the mass of the filter before sampling, mg;
Q——Sampling flow, L/min;
480 - Time-weighted average allowable concentration specified in 8h, min.
Fixed-point monitoring is a method of measuring the dust concentration in a workplace using a fixed-point long-term or fixed-point short-time sampling method.
If the sampling instrument can not meet the continuous one-time sampling of the whole working day during the fixed-point sampling, it can be used for long-time sampling of more than 1h in the whole working day, or sampling for 15min in a short time. The 8h time-weighted average concentration of dust in the air is calculated as follows:
TWA=(C1T1+C2T2+...+CnTn)/8
TWA in the formula - 8h time-weighted average concentration of dust in air, mg/m3;
C1, C2, ..., Cn - long-term sampling or short-term 15min sampling to measure the dust concentration in the air, mg / m3;
T1, T2, ..., Tn - the working time of the worker under the corresponding dust concentration, h;
8 - 8h specified by the time-weighted average allowable concentration.
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