In some cases it is necessary to organize so air exchange that one amount of air was obligatory more than another. For example, at design of ventilation of two adjacent rooms, in one of which harmful substances are allocated. The amount of the deleted air from this room has to be more amount of stitched air therefore small depression is indoors created.
Humidity of air has a great influence on thermal control of an organism. The increased humidity (φ> 85%) complicates thermal control because of decrease in evaporation of sweat, and too low humidity (φ <20%) causes drying of mucous membranes of airways. Optimum sizes of relative humidity make 40 - 60%.
Shelters with a suction are characteristic that the source of harmful allocations is in them. They can be executed as the shelters casings in whole or in part concluding the equipment (hoods, showcase shelters, cabins and chambers). In shelters depression therefore harmful substances cannot get to room air is created. Such way of prevention of allocation of harmful substances indoors is called as aspiration. Aspiration systems usually block with starting arrangements of processing equipment the suction of harmful substances was made not only in a place of their allocation, but also at the time of education.
Stitched and exhaust systems have to be indoors correctly placed. Fresh air needs to be given to those parts of the room, where amount of harmful substances minimum, and to delete where allocations are maximum.
Such schemes of air exchange when in all room pressure is supported superfluous in relation to atmospheric are possible. For example, in shops of electrovacuum production for which lack of dust is especially important.
Under the pressure of air from a windward side external air will arrive through the lower apertures and, spreading in the lower part of the building, to force out more heated and polluted air through apertures in a building lamp outside. Thus, action of a wind strengthens the air exchange happening at the expense of gravitational pressure.
therefore temperature of an internal of the person remains to a constant (about 36,6 °C). This ability of a human body to maintain a constant temperature at change of parameters of a microclimate and when performing various work on weight is called as thermal control.
On a way of movement of air ventilation happens to natural motivation (natural) and with mechanical (mechanical). Perhaps also a combination of natural and mechanical ventilation (the mixed ventilation).
Hoods find broad application at heat and galvanic treatment of metals, coloring, a weighing and packaging of bulks, at various operations connected with release of harmful gases and vapors.
Action of all-exchange ventilation is based on dilution of the polluted, heated, damp air of the room by fresh air to maximum permissible norms. This system of ventilation is applied most often in cases when harmful substances, warmth, moisture are marked out evenly on all room. At such ventilation maintenance of necessary parameters of the air Environment in all volume of the room is provided.
One of necessary conditions of healthy and high-performance work is ensuring purity of air and normal weather conditions in a working zone of rooms, i.e. space up to 2 m high over the level of a floor or platform where there are workplaces.
In production rooms in which perhaps sudden receipt in air of a working zone of large amounts of harmful vapors and gases, along with the worker is provided the device of emergency ventilation.
Except these parameters which are the main it is worth to remember about the atmospheric pressure P which influences the partsialny pressure of the main components of air (oxygen and nitrogen, and, therefore, and breath process.
Local forced ventilation serves for creation of the demanded conditions of the air environment in a limited zone of the production room. Treat installations of local forced ventilation: air souls and oases, air and air and thermal veils.
Cabins and chambers represent capacities of a certain volume in which the works connected with allocation of harmful substances (sanding and drobemetny processing, painting works, etc.) are performed.