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Posted By paul debney
At what size does a dust particle become 'respirable' as opposed to 'inhalable'?
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Posted By IanD
Thinking back to my old pit days it used to be 7 - 11 microns
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Posted By Keith E
Depends which standard you are working too:
Think US use 5microns
UK use 7 microns
Search web for the Johanesberg Curve - not sure spelling is correct - (as in South African city)
You should also be able to find a graph plotting particle size against inhaled region of the lungs
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Posted By Dave Wilson
This was in the first ACOP when the original COSHH Regs came out, if memory serves me right!
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Posted By David O'Hara
10 microns I think!
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Posted By Dave Wilson
10 does it for me!
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Posted By Kevin Walker
Hi
There seems to be a little confusion in the answers so far:
Total Inhalable Dust: is generally less than 100 microns in diameter. The exposure standard or WEL for this is less than 10 milligrams/m3.
Respirable Dust: is 5 microns(diameter)and less as get get right into the lower levels of the lungs. The exposure standard or WEL for this is less than 5 milligrams/m3.
cheers
kevin
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Posted By Philip McAleenan Depending upon the size of the particles, inhaled substances may · Be filtered off by the nasal hairs or deposited in the upper respiratory tract to be spat, sneezed or coughed out of the body, (greater than 10 microns in diameter), · Settle in the mucus covering the bronchi & bronchioles and are then wafted up by tiny hairs towards the throat (5 microns - 10 microns in diameter), or · Reach and settle in the lung tissue (less than 5 microns in diameter). Fibres, such as asbestos, which predispose to disease, have a length to diameter ratio of 3:1 with a diameter of 3 microns or less; the longer the fibre the more damaging to the lungs it will be. Note: here that coughed up particles may again enter the body via the digestive tract. See also http://www.parrett.uk.com/dustmeas1.htm Philip
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Posted By Paul Leadbetter
Don't forget that inhalable / respirable curves are based on aerodynamic diameter not physical diameter. If we assume that the particles are actually spherical, the aerodynamic and physical diameters will only be the same if the specific gravity of the particles is 1.
Paul
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Posted By Adrian Watson
The simple answer is there is no simple answer! There is a standardised set of curves for total inhalable, thoracic and respirable particles for a healthy normal person breathing through their nose. The curves are specific for a 1450-mL tidal volume (moderate to heavy activity) at the rate of 15 respirations per minute. (The diagram can be found on the SKC website). The median figure for total inhalable particles is 50 um EUDS, thoracic particles is 10 um EUDS and respirable particles is 4 um EUDS.
Regards Adrian Watson
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Posted By Adrian Watson
The simple answer is there is no simple answer! There is a standardised set of curves for a healthy normal person breathing through their nose. The curves are specific for a 1450-mL tidal volume (moderate to heavy activity) at the rate of 15 respirations per minute. (The diagram can be found on the SKC website). The median figure for total inhalable particles is 50 µm EUDS, thoracic particles is 10 µm EUDS and respirable particles is 4 µm EUDS.
Regards Adrian Watson
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Posted By Dave Wilson
Adrian you scare me some time mate!
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