air cooling and ventilation
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Air cooling and ventilation
Sheikh Kashif
Faiz
Vaswee Dubey
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What Is Industrial Ventilation?
Environmental engineers view:
The design and application of equipment forproviding the necessary conditions for maintainingthe efficiency, health and safety of the workers
Industrial hygienists view:
The control of emissions and the control ofexposures
Mechanical engineers view:
The control of the environment with air flow. This canbe achieved by replacement of contaminated air withclean air
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Hazards of Poor or No Ventilation
Lack of oxygen (headache, fatigue, Asphyxiation,
particularly in confined spaces)
Excessive heat, cold, and humidity
Toxic fumes (e.g.- Lead, cadmium, zinc)
Toxic vapors (e.g.- Benzene, toluene, TCE, MEK)
Toxic gases (e.g.- Hydrogen Sulphide, ammonia)
Dusts (causing poisoning or gradually reduced lungcapacity)
Fire/explosion
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Control philosophy
The correct recognition and careful
evaluation of the hazards are extremelyimportant and will constitute the basis
of appropriate control measures
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Generalized Diagram:--
Methods of Control
Desired control priority for chemical hazards
1. Source control
2. Pathway control
3. Receiver control
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Pathway Controls
Pathway controls generally are not as desirable as
source controls:-
Exposures are reduced, but not eliminated
(general ventilation)
The source hazard still remains
Pathway controls often are costly
Operation cost
Pathway control systems must be maintained
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Industrial Ventilation
Ventilation is a primary engineering control
available to eliminate or reduce the
concentration of gases, dusts, vapors,
smoke, and fumes present in the work
environment .
Ventilation is defined as the process of
supplying air to, or removing air from, any
space by natural or mechanical means.
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Purpose
To dilute airborne contaminants to
acceptable levels
To prevent hazardous air contaminants fromdispersing into the working environment
(LEV)
To prevent fire and explosion
To create a comfortable environment in the
plant - i.e. The HVAC system
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Types of Ventilation
General Dilution Ventilation(Pathway control)
- Mechanical Ventilation (involves Fans)
- Natural Ventilation(with natural air movement caused by
thermal gradient or any other)
Local Exhaust Ventilation (Source control)
Heating Ventilation and Air conditioning
System (to control temp. & humidity)
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Natural Ventilation MechanicalVentilationPreferred if significant
health hazards exist
General or Dilution Ventilation
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Clean AirSupply
Zone of ContaminantRelease
Operators BreathingZone
DischargeOpening
Direction of air flow must remove contaminants from workersbreathing zone
Principle of General Ventilation
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Recomme
nded
Practices
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General Dilution Ventilation
If (TLV
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Local Exhaust Ventilation-Source
Control
Capture or contain contaminants at their source
Typical Local Exhaust
Ventilation system
Components of Local
Exhaust SystemDuct
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Hoods - any point where air is drawn into the
ventilation system to capture or control
contaminants.
Ducts - the network of piping that connects the
hoods and other system components.
Fan - air-moving device that provides the energy to
draw air and contaminants into the exhaust system &
through the ducts and other components.
Air Cleaner - a device to remove airborne
materials that may be needed before the exhaust air
is discharged into the community environment.
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Use of Enclosures
--ed power consumption
-- less collection efficiency
--ed flow rate to have sufficient
capture velocity
-- more collection efficiency
--less flow rate required
--less power consumption
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Benefits of ENCLOSURES
Using techniques such as enclosures,
control capabilities are maximized
Air volumes requirements are drastically
minimized
Reduces required make-up air and
associated costs
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VENTILATION IN GARMENT INDUSTRIES
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TEMPERATURE
Cold temperatures are rarely a
problem for workers in garment
factories. Occasionally, workers inthe computer design rooms
experience cold temperatures.
Such environments are optimal for
the computer and not for the
workers.
Many garment workers
experience
hot, humid conditions, especiallythose in the ironing section.
There
are a number of control
measures
that can be introduced to reduce
the temperature.
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Temperature affects
productivity
A workers ability to do his/her job is affected byworking in hot environments. One of the mostimportant conditions for productive work ismaintaining a comfortable temperature inside the
workplace.
There are two main ways in which heat (or cold)gets into the factory:
Directlythrough windows, doors, air bricks etc;
Indirectlyby conduction through the actual fabric ofthe building namely the roof, walls and floor.
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There are a number of measures thatmanagement can take to try to reduce thesuns heat from entering the factory. These
include:
ensuring that the external walls are smooth intexture and painted in a light colour to help to
reflect the heat
improving the heat reflection of the roof
improving heat insulation of walls and ceilings
ensuring that the factory is shaded as far as
possible by natural means (trees, bushes,hedges etc) or with shades on windows, doors
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Controlling heat in the workplace
There are a number of basic approaches to tackling heat
hazards in garment factories:
ENGINEERING CONTROLS :
the use of increased general ventilation throughoutthe factory by opening windows, by ensuring that airbricks, doors etc are not blocked
the use of spot cooling by the use of fans to reducethe temperature in certain sections of the factory
the use of local exhaust ventilation systems in hotspots such as the ironing section to directly removethe heat as close to the source of the heat as possible
the use of air conditioners/coolers.
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CHANGING WORK PRACTICES :
increasing the number and duration of rest periods
introducing job rotation so that workers are notalways doing so-called hot work
doing hot work in the coolest part of the day
providing more workers to reduce the work load sothat workers spend shorter times in hotenvironments.
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In garment factories fans are located to
reduce the temperature in
certain locations. Here these workers
have fans behind them to cool down this
work
area.
Fans are used throughout garmentfactories to reduce the
temperature.
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National Standard for workplace
temperature
Prakas 147 on Thermal Environment at the Workplacespecifies:
Employers shall create a thermal environment that meets
acceptable standards.
The thermal environment shall be in conformity withworkers health and shall not disturb their work.
The thermal environment shall be measured by thetemperature shown on the thermometer at theworkplace.
In a building or a workshop with normal condition, each
worker shall have a space of at least 10 cubic meters.
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The workplace shall be protected from the ultra heat of the sun. The
production method which does not generate heat should be
adopted.
If the production generates extreme heat, the employer shall reduce
the heat by:
- having the heat generating parts insulated
- having the heat absorbed and diverted from the original source.
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Ventilation
It is not only essential to provide a comfortabletemperature inside the factory, one must also ensure :
an adequate supply of fresh air
the removal of stale air
the prevention of any build up of contaminants (dust,
spot cleaning chemicals, etc).
Many Cambodian garment factories rely on the principle of general
ventilation by allowing the free flow of air through the factory from one side
to the otherreferred to as horizontal air-flow.
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General ventilation in a
factory: if you have ventilation
systems or freestanding fans in thefactory, make sure thatthey increase the
natural flow of airthrough the factory andnot try to blow airagainst any prevailingwind.
ensure that hot, staleair that rises to thefactory roof can easilybe removed and
replaced with fresh air.
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make sure that all fansare well maintained andregularly cleaned so that
they work efficiently.
ensure that the air-flowto and from fans is notblocked .
try to ensure that anyhot processes such asthe ironing section issited next to the down
wind wall so that theheat is extracted directlyoutside rather than beingspread around thefactory.
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In cases where there is a build up of contaminants or heat in specific
areas of the factory, local exhaust ventilation has to be used to
remove the hazard. This type of ventilation uses suction and hoods,
ducts, tubes etc to remove the hazard as close to the source aspossible and extract it to the outside environment. It works on a principle
similar to that of a vacuum cleaner but on a much larger scale.
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National Standard for
ventilationPrakas 125 on Air Circulation and the Cleaning of the Workplacerequires:
An employer shall make an arrangement to have a good/cleanatmosphere at the workplace in order to maintain the health andsafety of the employees.
Air circulation in a workplace without a dirty atmosphere may bepossible by blowing in air naturally or artificially.
If dangerous substances in the workplace cannot be eliminated, theemployer must remove the hazard as close to the source as possibleto the outside environment in accordance with the EnvironmentalProtection Law.
This regulation also specifies the need for employers to providethe appropriate personal protective equipment if these hazardscannot be controlled by general or local exhaust ventilationsystems.
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Checklist for Temperature and
Ventilation
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Thank you.
References: http://www.globalsources.com/si/AS/Qingdao-
Xinmaosen/6008847210245/pdtl/It-
is/1059121934.htm
29 October, 2014 5:14 p.m.
http://betterwork.com/cambodia/wp-
content/uploadshttp://betterwork.com/cambodia/
wp-content/uploads/2013/05/OSH-manual.pdf29 October, 2014 5:14 p.m.
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