basic principle of ventilation
The basic principle of ventilation reads: "Give the air in the clean zone and benefit from the dirty." Consequently, when general ventilation particularly essential to determine where they will "clean" and "dirty" zone.
The allocation of dust (especially large), heavy gas fumes in the absence of convection currents "dirty" zone will be lower, near the floor. In the presence of heat flow zone of greatest concentration of harmful substances, as a rule, is superior. If the power of heat is insufficient, such a zone can be mean (in welding shops).
If local exhaust its area determined by the location of shelters, from which the exhausted air. At the zonal extract, which is an intermediate stage between local suction and general ventilation, the location of the receivers of air pollution is mainly dictated by placement of lesions of harmful emissions.
Zone hood yet distributed is relatively small. Nevertheless, the informal allocation of toxic gases (random breaks) or minor - dust discharges at certain points, when the shelter is not possible, use zonal extraction is justified. Receivers hazards in this case are usually funnel and shelevidnye pumps - straight and curved.
To delete a gaseous pollutant, as well as vapors, mists and aerosols or small amounts of dust are most effective local pumps with full or partial refuge chamber selections.
In all these cases, you should strive for full shelter (kapsyulyatsii) machines or devices that produce hazards. Kapsyulyatsiya - the most advanced and cost-effective method for localization of industrial hazards. Enclosure, rack, collapsible shelter for complex or cumbersome machinery, finally, the conclusion of the machine or apparatus is fully in the cabin (without the presence of people in it) the best way to prevent hazards in the room.
Kapsyulyatsiya of the equipment that meets the sanitary and technological requirements - a vast field of joint activities of technologists and specialists in ventilation. Only in this joint participation can be more when designing the machine or machines to provide adequate ventilation, which would be organically incorporated into the overall design, do not impede the process and would have been valuable in respect to sanitary.
If you can not complete kapsyulyatsii with less advanced local shelters and domestic pumps. These include parasols and veils, the suction panel, board and slotted pumps, casings, built on the principle of trapping flame hazards, funnel, based on the same principle, display cover for manual work, etc.
Local shelter or local suction to prevent the ingress of harmful substances in the breathing zone of workers. Local suction only good when he removes the hazard on the principle "from working."
Often the source of hazards - vat, furnace, etc. - "harboring" an umbrella under which the worker resides. This shelter is absolutely unacceptable. Fig. 1 shows the position of the head of the working of the source of hazard, covered with an umbrella. Aspirator device of this type with the direction of flow hazard "on the desktop" should recognize the wrong.
If the shelter of the unit (tub, bath, furnace) is impossible and the worker must bend over the source of hazards, there may be solutions: either the on-board suction, or suction panel located opposite the working and deviates from it flow hazards. In some cases, a combination of both. Proper scheme of local exhaust for this case is shown in Fig. 2.