B3 Ollie Flashcards
Ventilation
General Dilution Ventilation :
The introduction of fresh air in order to dilute airborne contaminants to a safe level
Local Exhaust Ventilation :
A system of removing contaminated air close to the point of production
General Dilution Ventilation
Natural ventilation: Flow of fresh air Mechanical/force d ventilation: Mechanical supply needed to: Provide oxygen for breathing Remove excess heat Dilute and remove odour Dilute and remove workplace contaminants (harmful to health and flammable)
Dilution Ventilation (1)
Low toxicity Multiple s ources Low concentrations Steady and low rate of release Workers are positioned at 90 degrees to airflow Must not interfere with airflow to LEV systems
Dilution Ventilation (2)
Must control exposure to below the WEL
Must maintain flammable sources to 10% of the LEL Not practicable to extract at source
Not dust
Heat loss not a problem
Dilution Ventilation - Advantages
Advantages:
Quick and simple
Cheap to install and run Few moving parts to service Failures are obvious
Dilution Ventilation - Dis-advantages
Disadvantages: Causes uncomfortable draughts Air flow may be uncontrolled Positive pressurisation may occur Only suitable for nuisance contaminants Benefit is not universal
Dilution Ventilation -Design
Rate of emission of chemical contaminant
Size of the workroom
General ventilation rates (8-36l/s ec/occupant) Seas onal changes
Poor mixing/airflow/pockets of stagnation Workers located downstream of contaminant Maintenance
LEV - Design
The size,shape and position of the source
The physical nature of the contaminant
The speed and direction of the contaminant
The rate of generation of the contaminant
The nature of the operation which generates the contaminant The position of the plant or machine operator
Local air movement due to general ventilation
Types of LEV Hood
Enclos ing (Partial/full enclosure) Receiving (Receptor hoods – canopy hoods and others ) Capturing (Captor hoods)
Receptor Hoods
Be big enough to receive the contaminant Emptied as fas t as it’s filled
As near to the process and source as possible As enclosing as possible
Shielded from draughts
Captor Hoods
Fixed, movable, low volume high velocity (LVHV)
Hood has to generate sufficient airflow at and around the source to capture and draw in the contaminant-laden air
Capture velocity:
Air velocity required to capture contaminant
Face velocity:
Air velocity at face of hood
Capture zone:
Area around hood where air velocity is sufficient
Capture Hoods - Maximising Performance
Maximise enclosure
Hood design - flanges
Capture zone must include working zone Training of operatives
Testing/trying using smoke tubes and pellets
Ductwork
Airflow (duct velocity) sufficient to keep particles
suspended Robust
Changes in direction kept to a minimum
Smooth junctions
Access points for cleaning May be flexible
Airflow must be balanced
Air Cleaners
Air filters (HEPA High Efficiency Particulate Air) Particulate dust and fume collectors
Devices to remove mists , gas es and vapours Needed because:
Harmful nature of contaminants Air recirculation Environmental considerations
Bag Filters
Fabric filter with shaker Hole in filter
Wrong filter
Shaker failure
Wet material
Electrostatic Precipitator
Very effective on oil must Potential for fires
Casing prone to corrosion
Fans -General
Centrifugal or axial
Selectiondepends on:
Airflow Resistance Contaminant Space Flammability Noise
Fans - Centrifugal
Good for high resistance
Often used for smaller volumes Backward curved blades are better
Fans -Axial
Cased axial
Belt driven axial
Bifurcated axial (least efficient but useful for flammable and corrosive materials)
Good for high volume low resistance air movement as in general ventilation.
Flue/Stack
Sufficient dis tance from air inlet
Design to avoid entry of water/vermin
Environmental cons iderations
Standards of emissions s et by Environment Agency/Local Authority Permit maybe required under The Environmental Permitting Regulations /Pollution Prevention and Control Regulations
Monitoring and Maintenance of Controls - COSHH Regulation 9
Plant and equipment in good repair, efficient state LEV every 14 months
Monitoring and Maintenance of Control Measures - LEV Requirements
LEV every 14 months Weekly check (ACOP): Ensure LEVis always on Observe condition of booth Observe visible ducting/dampers Observe evidence of failure e.g. odour, deposits Observe any pressure/flow device Undertake minor service work e.g. filter bins Records
Monitoring and Maintenance of Control Measures - Thorough Examination and Test
Examiner s hould refer to:
LEV system commissioning report
The LEV us er manual
The log book for the system
The previous LEV s ys tem s tatutory report
Confirmation that there have been no changes to the LEV, layout or process since the last test
Thorough Examination and Test - Stages
Stage 1:
A thorough visual examination to verify the LEV is in efficient working order, in good repair and in a clean condition
Stage 2:
Measuring and examining the technical performance to check conformity with commissioning data
Stage 3:
Assessment to check the control of worker exposure
is adequate
Pitot Static Tubes -PressureTest
Glass /steel tubes consisting of two concentric tubes
Positioned in ductwork facing direction of airflow
The device deduces the airs peed by measuring the pressure rise (velocity pressure) caused by the airflow
Pressure exerted at holes in sides of the tube can be used to measure static pressure
Rotating Vane Anemometer - Face Velocities
Connected to meter
Lose precision below 0.25m/s
Some intrinsically safe
Do not touch vanes
Not suitable for ducts or narrow openings
Several readings taken at hood face and average taken
Hot Wire Anemometer - Face Velocities
As the air moves over the heated wire, the wire cools
The amount of cooling is proportional to the airs peed, and this is calculated electronically
No use in flammable atmospheres
Require regular calibration
Windshield must be exactly aligned with airflow
Assess Control Effectiveness
Challenge tests with smoke with the process running, to check for
smoke leakage, eddying and breathing zone encroachment
Dust lamp tests with the process running to check for escape of dust or mist
Observation of the way operators work,whether they are using the methods specified and whether these methods are sustainable
Test Records
Name and address of employer Identification of LEV and process Date of last test
Test conditions
LEV design performance Method of test Equipment used
Date of test
Name and signature of tester Details of any necessary repairs Kept for 5years
Selection of PPE (1)
Nature of the hazard
Duration and frequency of use Other risks from work activity Compatibility
Ergonomic considerations Communication requirements Maintenance and storage Training required
Selection of PPE (2)
Fit and comfort Pers onal choice/employee acceptance Ethnic/religious considerations Pers onal fitnes s levels Durability of the PPE Cost British standards (BCE markings)
Personal Protective Equipment at Work Regulations 1992 - Requirements
Application
Provision of PPE
Compatibility
Assessment
Maintenance and replacement Accommodation
Information, Instruction and Training Use of PPE
Reporting Loss or Defect
Protection
Solid particles Chemical splash Gases and vapours Molten metal Non ionising radiations Glare Spectacles Goggles Face shields
Hand Protection
Cuts and abrasions Temperature Vibration Irritation and dermatitis Toxic and corrosives
Hand Protection - Types
Natural rubber:
Not suitable for solvents , strong acids or alkali
Nitrile:
Not suitable for strong acids or alkali
Neoprene:
Can be used for strong alkali
Hand Protection - Considerations
Factors to consider:
Breakthrough times
Penetration
Degradation
Possible problems: Sensitisation Sweating Lack of touch Lack of dexterity
Barrier Creams
Limited protection and information available
Workers may not apply them properly, leaving part of their skin uncovered
Variation in application
Protection may be removed while working without workers noticing Suncream
Whole Body Protection
Low risk - lab coats
Chemical
High visibility Mechanical - kevlar
Temperature
Respiratory Protective Equipment - Considerations
Oxygen level Substances present Hazardous effects Form Concentration WELs Additional hazards Length of wear Decontamination Face fit
Assigned Protection Factor (APF)
Concentration of contaminant outside face-piece divided by Concentration of contaminant inside face-piece:
Simple ratios o no units
Level of respiratory protection that can realistically be achieved by 95% of trained wearers
Based on survey of 10samples in lab
Gives measure of efficiency of RPE Higher the RPE, better efficiency
Minimum Protection Required (MPR)
Concentration of contaminant outside face-piece divided by the prescribed WEL
WEL is maximum allowed
In practice give allowance of twice the MPR
Types of RPE
Respirators
Filter contaminated air - not suitable for oxygen deficient atmospheres
Breathing apparatus
Independent air supply
Types of RPE-Respirators
Filtering face-pieces
Half-mask respirators with replaceable filters Full-face mask respirator with replaceable filters
Power assisted respirators with replaceable filters
Filtering Face-pieces
Particles and aerosols Standard: EN149: 2001
FFP1 – APF of 4
FFP2 – APF of 10
FFP3 – APF of 20
Particle Filters
Particle filters not suitable for gas es Marked P1,P2,P3 – white in colour
P1 low efficiency/P3 high efficiency TH for powered
respirators
TM for hoods
Change daily/hard to breathe through/damage Expiry dates
Gas/VapourFilters
Class 1(lowcapacity)toClass 3(highcapacity)
Colour coded for different substances e.g. inorganic gases and vapours – grey
Also marked for powered respirators (THor TM)
Change filters as instructed by the manufacturer, e.g.
single us e only or 50 hours /damaged/contaminant
tested
Generally gas filters last longer than particle filters
Expiry dates
Combined Filters
Markings for particles and vapours e.g. A2P3 — organic vapour filter with capacity class 2 and high efficiency particle filter
RPE - APF Values
Filtering Facepiece: 4-20 Half Mask:4-20 Full Face Mask:4-40 Air fedvisor:10-40 Compressed airline mask: 10-100 SC Breathing Apparatus : 40-2000
Breathing Apparatus
Separateair supply Fresh air hoses Compressed air line Self-contained breathing apparatus (SCBA) Escape sets
Face Fit
Filtering face-piece – qualitative
Half masks , full face masks – quantitative
Testing required by COSHH/CLAW/CAW ACOPs
Qualitative test – taste
Not needed for hoods /helmets /visor/blouses
Face Fit - Quantitative
Particle counting tes t (e.g. Portacount Plus ) Negative pressure device
Numerical value: required Full facemasks:2000 Half masks:100 Filtering facepieces:100 Competence: Fit 2Fit RPE Fit Tes tProviders Accreditation Scheme
RPE - Inspection and Maintenance
COSHH Reg 8:
Test at suitable intervals
Thorough examination normally once per month
At least once every three months
Visual examination all parts - straps , face pieces , filters
Records kept; 5 years
Air quality BA every three months
