Dust and harmful gases must go through a certain transmission process before they can be diffused into the surrounding air from the pollution source, and then come into contact with the human body and enter the respiratory system, ** and other human organs, constituting a hazard to the human body. The effect of making harmful substances from a static state to being suspended in the air and spreading to the air becomes the dust and spread of harmful substances. Generally speaking, there are several reasons for the transmission of harmful substances. 1.Diffusion When the concentration of harmful substances is unevenly distributed in space, the harmful substances will move from the high concentration area to the low concentration area due to the effect of the concentration difference, and the propagation mechanism of this harmful substance is called diffusion.
2.External mechanical forces Machining and many other industrial production processes, as well as the movement of the person itself, can produce extrusion, shear, stretching, etc., on the processing and production objects, surrounding objects, and these forces plus gravity and buoyancy are collectively referred to as external mechanical forces.
Relatively dense substances such as dust used in air flow and transportation, if they are in still air, will settle on the surface of the object under the action of gravity and be removed from the air, which will not cause harm to the human body. However, in the process of many production and processing and personnel activities, because of the high-speed movement of blocks and granular materials in the air and the upward movement of cold and hot air, the surrounding air will be driven to flow with it, and this part of the air is called induced air. Due to the high speed of the induced air, it can carry harmful substances to move together, so that the harmful substances can be taken away from the pollution source and transported to the air to spread. Generally, the induced air is called the primary airflow, and the indoor airflow formed by the convection of ventilation or hot and cold airflow is called the secondary airflow. The secondary airflow has a large range of movement, which can realize the large-scale transportation of harmful substances. It is precisely because of the local induced air and indoor large-scale air convection, that is, the movement of primary airflow and secondary airflow, that harmful substances can be transferred from the source of pollution to the location of personnel.