For the chemical industry is characterized by: the presence of emergency ventilation and exhaust fans duplication. II both called the toxicity of harmful gay, coming up in the air of industrial premises. For the same reason in certain industries, in addition to ventilation and sealing, have resorted to measures of individual protection to workers, respirators and gas masks.
In all premises where possible accidental release of significant quantities of toxic substances (gases, fumes, dust) with an acceptable concentration of 5 mg/m3 or less, shall establish special automatic devices which signal the presence of air pollutant concentrations above the allowable. In such premises the emergency hood must automatically turn on the gas analyzers that are configured for a certain concentration.
Emergency ventilation shall be provided in all areas where possible sudden release of air toxic or explosive substances. Ventilation, the need for removal of harmful substances, provided the joint work of the permanent and emergency extraction. Emergency exhaust influx is not compensated for, air enters from an adjacent room and outside through normal openings or through special designed for emergency influx. Special openings are held only when significant amounts of air exhausted in cases where a room can do a lot of toxic substances with a permissible concentration of 1 mg/m3 or less. Emergency inlet openings are arranged in the form of movable transoms or gate opens automatically at start-up emergency hood.
Emergency hood are always mechanical. Usually applied axial fans, disposable in the openings of walls, and roof. Emergency systems are generally carried out without air ducts. The allocation of explosives fans and motors alarm systems should be in the explosion - a safe design.
Occasionally for emergency extracts used centrifugal fans with an extensive network of air ducts. This is desirable when heavy gases released in the cold. An example of such an emergency ventilation exhaust systems are in areas where there is a chlorine gas pressure or liquid chlorine. Hood is arranged mainly from the lower zone, being, in essence, no general exchange, and zonal. In some cases rationally approximate the exhaust funnel to the places most likely breakout hazards - to pipe joints, seals, hatches, etc. n
Amount of air that is necessary to remove the emergency hatch, the calculation can not be.
When assigning the performance of emergency systems are based on empirical data, operating with such a precarious notion that the multiplicity of exchange.
In appointing the air on the multiplicity must first take into account the height of the room. Then, one should bear in mind the degree of saturation of premises equipment, pipes and fittings, as well as the number of seats possible emergency release hazards. And, of course, must take into account the degree of toxicity expected selections.
Found in the literature is scant and contradictory information about the required Multiplicities exchange for emergency hood in a particular case. Often suggested that the switching systems, emergency exhaust the total multiplicity of exchange, to establish joint permanent and emergency hatch should be in the range of 7 to 15. Such an approach to the question can not be considered correct.