1. TRI MARTIANA

2.  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

3.  Natural  General  Dilution  LEV

4.  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

5.  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

6.  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 1. Supply or forced ventilation 2. Exhaust or induced ventilation

7.  dilution ventilation  dilutes contaminant to an acceptable level  comprises fans set in walls or roof  cheap and simple  limited application as a control strategy  local exhaust ventilation  captures contaminant close to point of generation  comprises hood, ductwork, filter, fan,outlet  good control of hazardous contaminants

8.  changes the whole workplace air over a given time period ie air changes per hour  limit to circumstances where:  exposure limit is high  low evaporation rate for liquids  slow evolution for gases  operators not close to the point of generation  substance is quickly carried away from the operator

9.  rate of contaminant generation governs air changes per hour required  density of contaminant governs position of fans:  density >1 (ie solvents) - low level fan in wall  density <1 (ie hot gases) - high level fan in roof  problems include:  “dead areas” where poor airflow allows contamination to build up  heat losses due to high rate of air change

10.  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

11.  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

12.  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

16.  Hood or exhaust inlet  receptor hood contaminant directed into a large hood by fan assisted draught  captor hood contaminant captured by air flow close to point of generation low pressure large volume flow high pressure low volume flow (high velocity)

17.  ducting  straight with gentle bends and angled joints  sufficient air flow to prevent deposition of solids  access ports for cleaning and flow monitoring  filter or purifying system  cyclones, washers, electrostatic, bag filters

18.  Fans  axial flow fan airflow is parallel to the shaft of the impeller compact and fits neatly into ductwork  centrifugal fan air enters the impeller then is discharged at right angles  exhaust outlet  careful location to avoid: cyclic pollution effects of weather of air disturbance

19.  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

20.  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

21.  Major release (toxic) of localized sources of contaminants.  LEV consists of 4 parts: 1.Hoods (most important) 2.Ducts 3.Air cleaner device 4.Fan and motor

29.  The hood consists of 3 main types to contain and remove the air-borne contaminants. 1.Enclosures 2.Capturing hoods 3.Receiving hoods

30.  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)

31.  LEV capture or contain contaminants at their source before they are dispersed in the workroom  LEVs need to be maintained, inspected and tested regularly to ensure that it is performing adequately