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VENTILATION INDOOR AIR QUALITY

VENTILATION. PurposeSupply adequate oxygenPrevent build up of contaminantsMaintain comfortable environmentCommon typesGeneral dilutionLocal exhaust. VENTILATION. General dilution - ventilationAdds and removes air from work areasNatural convection; air movementFans (mechanical)Air can be cooled, heated (mechanical).

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VENTILATION INDOOR AIR QUALITY

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    1. VENTILATION & INDOOR AIR QUALITY

    2. VENTILATION Purpose Supply adequate oxygen Prevent build up of contaminants Maintain comfortable environment Common types General dilution Local exhaust

    3. VENTILATION General dilution - ventilation Adds and removes air from work areas Natural convection; air movement Fans (mechanical) Air can be cooled, heated (mechanical)

    4. GENERAL VENTILATION Dilution ventilation appropriate if (i) Small quantities of contaminants (ii) Contaminants released at uniform rates (iii) Sufficient distance - worker and source (iv) Contaminants of low toxicity (v) No need to filter before discharge Examples offices, car parks, industry

    5. GENERAL VENTILATION Components Fans Ducts Inlet-outlets, heating/cooling, filtration Disadvantages - general dilution Difficult to control exposure near source Large volumes of air moved Can be more costly Cannot be used with highly toxic materials

    6. VENTILATION Local Exhaust Ventilation (LEV) Captures contaminants close to source Shifts small volumes at air of high speeds Removal not always 100% Ranks fifth in hierarchy

    7. LOCAL EXHAUST VENTILATION LEV System Hood Ducts Air cleaner (if needed) Fan Principles of LEV Enclose source as much as possible Pick up points as close to source as possible Air withdrawn at sufficient rate to remove contaminants (critical)

    8. LOCAL EXHAUST VENTILATION Advantages of LEV Requires less air flow Contaminant not spread in workplace Can be very effective Can recover reusable materials Disadvantages Can be difficult to design Only effective close to source

    9. LOCAL EXHAUST VENTILATION Uses of LEV Most common type Toxic gases, vapours, fumes, mists Numerous industrial processes

    10. VENTILATION Evaluation of Ventilation (i) General Ventilation ( Natural dilution ) check location of windows, doors vents, check direction of prevailing breezes check air movement (eg smoke tubes) locate ‘dead’ areas check levels of contaminants

    11. VENTILATION Evaluation of ventilation (continued) (ii) General ventilation (mechanical) guidance and design (eg ASHRAE) measure volume of air supplied and exhausted check air movement locate dead areas check air temperature check level of contaminants (if sources) check location of air intake-contaminant sources

    12. VENTILATION Evaluation of ventilation Exhaust ventilation system Capture velocities/air movement ( anenometer ) Suction/static pressure in ducts ( manometer ) Filter performance Fan speeds

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