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Ventilation Systems As Control Measures. Dr. Lim Jac Fang Doktor Kesihatan Pekerjaan JKNSabah. Introduction . A good and effective ventilation system is necessary in a workplace which have processes that emit air contaminants such as dust, fumes, mists or vapours.

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Ventilation systems as control measures l.jpg

Ventilation Systems As Control Measures

Dr. Lim Jac Fang

Doktor Kesihatan Pekerjaan

JKNSabah


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Introduction

  • A good and effective ventilation system is necessary in a workplace which have processes that emit air contaminants such as dust, fumes, mists or vapours.

  • Substitution or enclosure method

  • Simple, cheap and effective


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Types of Ventilation

Natural

General

Dilution

LEV


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Natural Ventilation

  • Natural movement of air entering and leaving openings such as windows, doors, roof ventilators as well as through cracks and crevices of a building

  • Heated air rises, cool air below


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General Ventilation

  • A method of improving or maintaining the quality of air in the work environment with airflow

  • A room or an entire building is flushed by supplying and exhausting large volumes of air throughout the area

  • Supply or forced ventilation

  • 2. Exhaust or induced ventilation


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Dilution Ventilation (DV)

  • DV consists of general ventilation

  • Uncontaminated outside air + inside air = diluting and reducing the concentration of air contaminants to acceptable levels to which a worker can be safely exposed for eight hours a day


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LEV

  • Capture or contain contaminants at their source before they escape into the work room environment

  • System consists of one or more hoods, ducts, air cleaner and a fan

  • LEVs remove contaminants rather than just dilute them


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Use of Natural Ventilation

  • Not suitable for processes which emit dust, fumes, mists or gas

  • Rooms for chemical storage +

  • 25% of floor area

  • Half the ventilating area should be between floor level and a height of 2.25m from the floor


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Use of Dilution Ventilation

  • DV is usually applied to the control of contaminants in situation meeting these criteria:

  • To control vapours (+organic) from low toxicity solvents

  • To control contaminants released over such a large area or in such a manner that LEV is impossible, impractical or prohibitively expensive


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  • DV is prohibited – control emission of very toxic air contaminants e.g., formaldehyde or other carcinogenic chemicals

  • For effective DV, the exhaust outlet and air supply must be so located that all the air employed in the ventilation passes through the zone of contamination


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Simplicity contaminants e.g., formaldehyde or other carcinogenic chemicals

Low original cost

Large volumes of dilution air needed

Employee exposures are difficult to control near source

Advantage Disadvantage


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Use of LEV contaminants e.g., formaldehyde or other carcinogenic chemicals

  • The most effective means of controlling air contaminants is to capture and remove the air contaminants at their source with LEV and to prevent them from being carried away by air currents into the breathing zones of the worker


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  • Hoods (most important)

  • Ducts

  • Air cleaner device

  • Fan and motor


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  • Enclosures

  • Capturing hoods

  • Receiving hoods


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Conclusion air-borne contaminants.

  • Ventilation – an effective way to control toxic air contaminants if substitution or enclosure method of control is not possible

  • DV reduces contaminant concentrations by diluting them with fresh air. (not for toxic emission)


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Thank You! they are dispersed in the workroom


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