Methods of localization of harmful emissions
General ventilation effectively and economically removes heat only in the absence of other hazards. The simultaneous presence vlagovydeleny, preventing aeration during the cold season, significantly reduces the efficiency of general ventilation.
Other hazards (gases, fumes, dust), evolved separately or together with heat and moisture, generally require devices hybrid ventilation.
Heat in its pure form is rarely encountered in the industry. Usually they are accompanied by vlagovydeleniyami, or gases and vapors, or dust, or more of these hazards together. In these cases, to assist general ventilation frequently arranged local pumps. This mixed ventilation, ie a combination of local suction to extract the general exchange, most prevalent in the industry. General ventilation in pure form or ventilation only with local suction devices are less common.
Obscheobmepnaya ventilation is used in special cases - for all types of hazards, except for the dust emission. Only rarely with a slight and scattered dust vydsleppp obscheobmepnaya ventilation is also used for dust control (eg, in printing on cardboard factories,
in storage of loose materials, etc.). In these cases, ventilation is designed with mechanical ventilation of certain areas of the room.
The allocation of gases and vapors, aerosols, and the hollow droplets of moisture and water mist general ventilation in some cases is the only acceptable solution. These special cases are typical of local suction device failure under the terms of technology.
However, if possible, shelter pockets of harmful emissions from the local suction device still has to be mixed ventilation. The fact is that even with a full cap-syulyatsii completely remove the hazard can not be - some of them breaks into the room. That is why we have to use general exchange extraction.
In SNIP II-F. 7-62 on the subject there is a direct order: "In areas with a simultaneous release of harmful gases and heat, or only harmful gases are lighter than air, except for local suction devices from industrial equipment, general exchange should include the hood from the upper zone of the premises in amounts not less than once per hour .
This requirement naturally applies to those cases where stand the heavy gases, vapors, mists and aerosols. It does not apply in cases of dust, because the general ventilation is ineffective. With heavy gases and vapors in the absence of heat release exhaust produced from the lower and upper zones.
Need to stipulate that the general exchange extraction in a single volume of the space is acceptable only for large cubic capacity of premises (2000 m3 and above). For small rooms, the multiplicity of exchange shall be equal to two or three. The volume of general exchange extraction can also receive 10-15% of the total volume of air removed local suction.