【11-28】Daily Tip for Occupational Health

Wear the appropriate personal protective equipment, and take timely action to prevent excessive dust accumulation

First of all, personal protection should be ensured by wearing dust masks and safety helmets

Wear protective clothing, a mask and goggles, as well as a safety helmet

Dust control measures: The key to preventing pneumoconiosis and coal dust explosions is to reduce the dust concentration in the workplace to levels that meet the standards specified in the regulations. To this end, comprehensive dust control measures are implemented following an eight-principle approach of \"replacement, water suppression, sealing, ventilation, protection, management, education, and inspection\" for prevention. Among them, technological innovation is fundamental, while wind, water, protection, and management are the key aspects. The so-called \"innovation\" refers to using technological advancements to address the root causes of dust generation at its source. In recent years, greater attention has been paid to the prevention and control of occupational diseases in the coal mining industry; more funds have been invested in mining processes, the working environment, as well as personal protective equipment. Production facilities have also been gradually upgraded and modernized. With further advances in mechanization, workers’ exposure to dust has decreased, resulting in significant improvements in dust prevention and control measures. The so-called \"wind\" and \"water\" approach refers to a dust control method that focuses on using water as the main element, with wind playing a supplementary role; it employs various measures such as sprinkling water to reduce dust, ventilation to remove dust, and purification of the air flow to control dust levels. The specific methods are as follows: 1. Wet drilling refers to the process in rock tunneling where pressurized water is sent to the bottom of the hole via the drilling machine, thereby wetting and flushing out the dust in the borehole, causing it to turn into a slurry that is then discharged from the borehole. This allows the vast majority of dust to be contained within the blast hole. By using wet drilling, the dust concentration can be reduced from 500–1400 mg/m3 in the case of dry drilling to 4–10 mg/m3, with a dust reduction rate of 90%–98%. Therefore, wet drilling is an effective dust control measure commonly used in drilling operations. Dry drilling can be employed only in areas with severe water shortages or when drilling into water-swelling rocks, in which case dry dust collectors should be used to capture dust. 2. Ventilation for dust removal and air purification – Diluting and removing mine dust through ventilation is one of the important measures for reducing the concentration of dust underground. Therefore, it is necessary to strengthen the management of tunneling ventilation, reduce air leakage, increase the air volume at the outlet of the air ducts, and properly control the wind speed. When the wind speed is too low, the coarse mineral dust will separate from the air and settle, not being expelled. According to experimental observations, when the wind speed in the tunnel reaches 0.15 m/s, mineral dust with a size of 5 μm or less can remain suspended, mix evenly with the air, and be carried away by the airflow. The regulations stipulate that the minimum wind speed in rock roadways during tunneling must not be lower than 0.15 m/s, which fully meets the requirements for the minimum wind speed for dust removal. By increasing the dust exhaust velocity, dust particles with slightly larger sizes can also be suspended and removed, which in turn enhances the dilution effect and reduces the concentration of mineral dust. As the wind speed increases, dust is lifted into the air, raising the dust concentration in the airflow; therefore, the regulations specify that the maximum allowable wind speed in mining areas is 4 m/s. In work areas with high dust generation, a high density of mineral dust, and relatively high temperatures, the dust exhaust speed can be increased appropriately. Ventilation for dust removal involves using an appropriate wind speed to expel the dust generated at the tunneling site, while minimizing the scope of contamination. To this end, a water curtain is installed in the tunnels through which air streams with high dust concentrations pass to purify the air flow. The arrangement of the sprayers should be based on the principle of covering the cross-section of the tunnel with a water curtain, and they should be placed as close as possible to the source of dust in order to reduce the range over which dusty air spreads. Another approach is to install water screens in the dust-generating tunnels, with an interval of 20 meters between them; it is most effective to install three sets of such screens at one end (the tunneling end). According to the results of on-site tests, the dust reduction rate reached 98.6%. 3. Blasting spray: Blasting is one of the main sources of mineral dust, and it can cause the dust to become airborne again, contaminating the air. Using spray water to control dust during blasting can yield good results. Spray watering involves using pressurized water, which is forced through a sprayer and, under rotational or impact forces, turned into fine droplets that are sprayed into the air. Its functions are as follows: ① Within the range of action of the fog, water droplets moving at high speed collide with suspended dust particles; these particles become moistened and then sink due to gravity ； ②The high-speed flowing mist creates a negative pressure that draws the dust-containing air around it into the mist, where it becomes moist and sinks ； ③Moisten and bind the settled dust particles to prevent them from flying around ； ④Increase the moisture content of coal to reduce its explosiveness ； ⑤Prevent the spread of explosion flames. 4. Sprinkling water during rock loading, washing the tunnel walls, and dust suppression at transfer points. Sprinkling water during rock loading is a method of manually applying water before and during the removal of rock. Washing the tunnel walls is a measure taken to prevent dust accumulated on those walls from being blown up again by wind or due to shock waves in the tunnel, thereby avoiding further hazards. The implementation of these two measures requires manual intervention, and based on the author’s numerous on-site observations, it turns out that they are not consistently carried out during periods of high production volume; this represents a gap in dust control efforts. It is recommended that leaders and departments at all levels strengthen supervision and management of this task. The coal unloading ports at various transfer points are another source of dust proliferation. Article 150 of the Coal Mine Safety Regulations clearly stipulates: “Mines must establish a comprehensive dust suppression water supply system.” Mining faces without dust-proof water supply system pipelines shall not be put into production. Sprinkler systems must be installed in the main haul roads, the return airways of the mining areas, as well as at the heads of all conveyors and transfer devices and at the coal unloading points. 5. Personal protection: Even after implementing the aforementioned dust control measures, a small amount of fine dust remains in the air; therefore, enhancing personal dust protection is also an important aspect of comprehensive dust control. The main tool for individual dust protection is a dust mask; currently, simple masks and specialized dust masks are widely used. Choose different dust masks based on the differences in the working environments, and ensure their proper use; in particular, workers in mining and shotcreting roles must not overlook the importance of personal protective equipment. In short, addressing the hazards caused by coal mine dust is a long and complex process. As long as we respect science, adhere to the principles of putting people first, keeping pace with the times, being innovative, and seeking truth and pragmatism, and strictly follow the relevant regulations and industry standards, while combining them with the eight-principle approach, methods, standards, and requirements for controlling dust, by promoting technological innovation, ensuring adequate investment in facilities, and strengthening the integration of management and supervision, the control of dust hazards in coal mines will achieve positive results.

Wear appropriate dust-proof protective equipment as required, and try to choose a location that is upwind