Occupational Hygiene Control Part2...3 Occupational Hygiene – Control of Chemical Health Risks – Part 2 Frances Wright A Typical LEV System Enclosing Capturing Receiving Source:

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Occupational Hygiene – Control of Chemical Health Risks – Part 2Frances Wright

Occupational Hygiene – Control of

Chemical Health Risks – Part 2

Frances Wright

Occupational Hygienist Wright Environmental Services

Module OSH10020

Part 1

Hierarchy of Control

Part 2

Ventilation and Respiratory Protective Equipment

Occupational Hygiene – Control of Chemical Health Risks

Identify Processes

& Workers

Evaluate the RiskControl the Risk

Document,

Communicate &

Review

Identify the Chemical Hazards

CHEMICAL

RISK ASSESSMENT


� Elimination

� Substitution

� Process changes

� Engineering controls

� Automation

� Containment

� Local Exhaust Ventilation

� General Area Ventilation

� Administrative controls

� Respiratory Protective Equipment

Least Preferred

Most preferred

Dilution

ventilation

Local exhaust

ventilation

Dilution Ventilation• Dilutes concentration in the general area

• USES:

• Operator is removed from source

• Low toxicity substances

• Low level concentrations

• Odours

• Improve indoor air quality

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Dilution Ventilation• ADVANTAGES:

• Less maintenance than LEV

• Lower costs

• Independent of operator

Dilution Ventilation• DISADVANTAGES:

• Does not completely remove contaminant

• Can spread the contaminant around workplace

• Make up air (heating/cooling)

Dilution Ventilation• DESIGN

• Move the contaminant away from worker

AIR EXTRACT AIR INSOURCE

Dilution Ventilation

Local Exhaust Ventilation� Removes the contaminant from the workplace

at the source

LEV - Components

• Hood – Contaminant to enter

• Ducting – Transports contaminant

• Air Cleaner – Cleans air

• Air Mover – Fan to move air

• Discharge Point – Safe emission point

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A Typical LEV SystemEnclosing

Capturing

Receiving

Source: HSE

The three basic types of LEV hood

Full Enclosure - Isolator/Glove Box Partial Enclosures - Fume Cupboard

Room Enclosures –Spray Booth Receiving Hoods - Circular Saw

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Capturing Hoods – Evaporation LEV DesignImportance of Enclosure

Increased Efficiency

LEV Design� Capture Velocity

� Face Velocity

� Transport Velocity

� Capture Zone

LEV DesignMaintenance and Testing

Smoke Test

Hot Wire Anemometer

Capture Zone

LEV DesignHood Placement — Capture Contaminant

LEV Design

Hood Placement – Move the contaminant from the

breathing zone

Direction of

air flow

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LEV Design

Hood placement – Move the

contaminant from the breathing

zone

LEV Design

LEV Design LEV Design

LEV Guidance� Heath and Safety Authority (Ireland)

� Due for publication in 2014

� Health and Safety Executive (UK)

� “Controlling airborne contaminants at work –

A Guide To Local Exhaust Ventilation”

Respiratory Protective Equipment � Air Purifying� Filters/Reduces the contamination

� Clean Air Supply� Provides uncontaminated air supply

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Air Purifying Respirators� Particulates

– Dusts, fumes, fibres, mists

� Gases and vapours

� Combination filters

Air Purifying Respirators� Non – powered

� Powered

Air Purifying RespiratorsNon powered

“Disposable” Half face piece Full face piece

Air Purifying RespiratorsPowered

Supplied Air RespiratorsClean Air Supply Via Air Line

Workplace Example Supplied Air Respirators - Air Line

Spray Painting - Isocyanates

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Workplace Example Supplied Air Respirators - SCBA

Self Contained Breathing Apparatus (SCBA)

Workplace Example Supplied Air Respirators - SCBA

Emergency/Rescue

Protection Provided Protection Factor (PF)

PF =

Ratio of the Concentration Outside RPE Versus Concentration Inside RPE

Concentration inside RPE must be below the Occupational Exposure Limit

Concentration Inside

Concentration Outside

Consider an asbestos atmosphere of 10 fibres / cc

Exposure limit 0.1 fibres / cc

Concentration inside mask

(PF10)

1.0 fibres / cc


(PF 50)

0.2 fibres / cc


(PF 100)

0.01fibres / cc

Rearrange the Formula : Concentration Inside = Concentration Outside

PF

Respiratory protection limitations� Not 100% efficient

� Contaminant concentration must be known

� Requires face fit and RPE programme

� Training essential

� Other staff not protected

� Communications difficulties

� Discomfort

� Always worn?

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Examples of uses of RPE

� Bottom of hierarchy of control

� Addition to other controls

� Short term or occasional use

� Maintenance

� Escape

Guidelines on Respiratory Protective Equipment

Dilution

ventilation

Local exhaust

ventilation

SummarySummary –

Respiratory Protective Equipment

� Air Purifying� Filters/Reduces the contamination

� Clean Air Supply� Provides uncontaminated air supply

Part 1


Part 2

Ventilation and Respiratory Protective Equipment

Occupational Hygiene – Control of Chemical Health Risks

Learning OutcomesHaving completed all of the learning activities associated with this

lecture, you should be able to:

� Apply the hierarchy of control measures to the management of

chemical hazards to health

� Give examples of control measures appropriate to different

health hazards

� Differentiate between local exhaust ventilation and dilution

ventilation

� Discuss the limitations on the use of respiratory protective

equipment, and provide the rationale for its use in different

circumstances

� Describe the different types of respiratory protective equipment

available.

Documents

Occupational Hygiene Control Part2...3 Occupational Hygiene – Control of Chemical Health Risks – Part 2 Frances Wright A Typical LEV System Enclosing Capturing Receiving Source: