Industrial Ventilation Silica - WorkSafe Queensland...Industrial Ventilation Silica Dr David...
Transcript of Industrial Ventilation Silica - WorkSafe Queensland...Industrial Ventilation Silica Dr David...
Industrial VentilationSilica
Dr David BromwichBSc(Hons), MAppSc(Med Phys, QIT), MSc(Occ Hyg, Lond), FAIOH, COH, PhD(Griffith)
Consulting Occupational Hygienist
Adjunct Associate Professor Centre for Environment, Population and HealthSchool of MedicineGriffith University
dbohs.com
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My Industrial Ventilation
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Sources of Respirable Crystalline Silica (RCS)
Construction Sandblasting
Jack hammering
Rock drilling, cutting, chipping or polishing
Brick or tile cutting and sawing
Concrete drilling, sawing, grinding and polishing
Tunnelling
Demolition
Asphalt milling
Tuckpointing
Stone countertop fabrication
Diatomaceous earth processing
Pottery production
Foundries
Work on linings of rotary kilns and cupola furnaces
Mining
Hydraulic fracturing
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Risk
0.25%0.5%2.5%
20%
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Risk
(%
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Respirable Crystalline Silica (mg/m3)
Lifetime risk of silicosis
ACGIH2010 Australia
1993
ACGIH1986
NIOSHAustralia
2005UK control
2002,
Hawke's Nest Tunnel
UK max2002
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Topics Historical context Toxicology
Dust Size
Free Radicals – age of dust
Hierarchy of Control & Industrial Ventilation Industrial Ventilation concepts Effectiveness of dust suppression with water Effectiveness of respiratory protection
Applying Industrial Ventilation concepts
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Historical Silicosis and Workers Compensation 1930’s in USA
Hawk’s Nest Tunnel (1927) USA About 1000 deaths (3000 workers)
Sydney Harbour Bridge (1923-1932) Many died from silicosis (250 stone workers)
Only 16 died from injuries
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Historic -1930
https://www.sciencespo.fr/silicosis/sites/sciencespo.fr.silicosis/files/ILO_Silicosis_Conference_1930_report_of_proceedings.pdf
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ILO 1930 Silicosis“The Relative Value of the Use of Water and of Ventilation in the Prevention of Silicosis”
To keep dust out of the air at the site where the stone was broken; water was very efficient, but the finest dust would pass any form of water
Ventilation is never 100% effective
Nor are water sprays for the very toxic fine silica particles
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Hierarchy of Control for Silica Elimination
Substitution
Isolation – control cabins
Engineering Controls New technology – water jet cutting
Water Sprays
Industrial Ventilation
Administrative Controls
Personal Protective Equipment Respiratory Protection
https://www.breton.it/
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Visible particulates
http://amienvironmental.com/
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Particle sizeNose
Mouth
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Industrial Ventilation concepts
Sucking and Blowing
Air flow away from face
Extraction close to source
Changing particle size
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Sucking and blowing
Many industrial ventilation systems (sucking air) are designed by people with an airconditioning background (blowing air)They often get it wrong
Adapted from McDermott 1976
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Imagine a black hole vacuum
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Imagine a black hole vacuum
Air flows from all directions
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Imagine a black hole vacuum Enlarge the hole
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Imagine a black hole vacuum Now join a pipe to the hole
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Imagine a black hole vacuum Capture zone
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Imagine a black hole vacuum Often contaminants escape…
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Shaping the airflow - flanges
https://www.nap.edu/read/4911/chapter/1
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Suction is not directional
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Industrial Ventilation concepts
Sucking and Blowing
Air flow away from face
Extraction close to source
Changing particle size
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Ideal flow is away from face
https://www.ccohs.ca/oshanswers/prevention/ventilation/hoods.html
Intended
Desired
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Industrial Ventilation concepts
Sucking and Blowing
Air flow away from face
Extraction close to source
Changing particle size
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Wet grinding benchtop
Source /www.cdc.gov/features/preventing-silicosis
HOOD
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Good design
90% of Industrial Ventilation design is with hood
If capture of toxic air is ineffective then Person breathes more toxic air
Larger vacuum / extraction fan needed – greater cost
Noisier
Many systems badly designed, even on tools
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HSE research (UK) RR926 - On-tool controls to reduce exposure to
respirable dusts in the construction industry - A review (2012) https://www.hse.gov.uk/research/rrhtm/rr926.htm
• On-tool LEV – reduces exposures by 90%• Hood design, suction• On-tool controls never completely eliminated exposure
•supplementary respiratory protective equipment (RPE)
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Industrial Ventilation concepts
Sucking and Blowing
Air flow away from face
Extraction close to source
Changing particle size
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Water Sprays
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Traditional water suppression
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Better water suppression
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Better water suppression
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Benchtops – saw silica dust control
Jared H. Cooper, David L. Johnson, Margaret L. Phillips, Respirable Silica Dust Suppression During Artificial Stone Countertop Cutting, The Annals of Occupational Hygiene, Volume 59, Issue 1, January 2015, Pages 122–126, https://doi.org/10.1093/annhyg/meu083
44.4
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Dry Wet Wet + curtain Wet + LEV
Resp
irab
le S
ilica
(m
g/m
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Tunnelling Brisbane has a number of new tunnels
Standard Practice is to supply fresh air to the cutting face
Air is filtered and returns along the tunnel
This is opposite of good practice, as filtration is never 100%
Other tunnel workers are exposed to respirable silica
https://accionacorp.blob.core.windows.net/
portofmiamitunnel.com
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Applying Industrial Ventilationto Respiratory Protection
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Air flow - inhalation
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Facial hair and RPE 1.3 cm/month = 150 microns/shift
Respirable dust 10 microns (0.01 mm)
Getting a good face seal on a respirator after a day's facial growth is as likely as a fence made of 6 m high powerlines will contain a mouse
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PPE Fit
Inhalation – air flows over surface of face (sucking)
Exhalation – air flows in a plume (blowing)
A face mask makes even more air flow over the surface of the face
Facial growth – holds face mask off face
A beard makes any face mask much less effective
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PPE
Source: https://www.abc.net.au/news/2018-10-12/what-is-the-dust-lung-disease-silicosis/10365604
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Seal to neck is important
Managing respirable crystalline silica dust exposure in the stone benchtop industry Code of Practice 2019 (Queensland)
https://www.worksafe.qld.gov.au/injury-prevention-safety/workplace-hazards/managing-respirable-crystalline-silica
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Silica dust control
Agglomerate dust with fine water spray
Remove this dust with well designed extraction ventilation Also use good respiratory protection
Quantitative Fit testing and training
Professional Respiratory Protection Program (not cheap!)
Thank YouDavid Bromwich
dbohs.com