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EH40 expert ?
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Muiryden  
#1 Posted : 09 March 2010 11:51:06(UTC)
Rank: Forum user
Muiryden
In EH40 many workplace TWAs are marked with a dash: For example : substance : 8 hr PPM mgm3 : comment "Hydrogen cyanide 74-90-8 - - 10 11 Sk" Does the dash mean zero and if so why is a "0" not shown? Many thanks in advance for any response.
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redken  
#2 Posted : 09 March 2010 12:06:59(UTC)
Rank: Super forum user
redken
74-90-8 is the Chemical Abstracts no( CAS) for hyrdrogen cyanide. The next two dashes are becuase it does not have short term exposure limits and the 10 11 are the long term exposure values. The Sk is skin. Look up the full entry in EH40/2005 Table 1 list
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Muiryden  
#3 Posted : 09 March 2010 12:17:40(UTC)
Rank: Forum user
Muiryden
Many thanks for the prompt reply, if there is no defined long term exposure limit but there is a short term one, where do I stand, is the limit "as low as reasonably practicable", is it zero PPM, one PPM two PPM, is it by reviewing historical occupational health data? Any guidance appreciated.
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Heather Collins  
#4 Posted : 09 March 2010 12:19:02(UTC)
Rank: Super forum user
Heather Collins
Wrong way round Redken. Hydrogen cyanide has no long term exposure limit, only a short term one. Makes sense if you think about what a nasty substance it is! 10 and 11 are the 15 minute limits in PPM and mg per cubic meter respoectively. Muiryden - having a limit of zero PPM is not the same as no limit having been set. In this case it is not appropriate to set a long term limit for this material because it's considered that it must be controlled within the strict short term limt due to the acute (very short term) nature of reactions to hydrogen cyanide.
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Heather Collins  
#5 Posted : 09 March 2010 12:24:02(UTC)
Rank: Super forum user
Heather Collins
Muiryden - have a read of the appendices to EH40. http://www.hse.gov.uk/pubns/priced/eh40.pdf It has this to say about short term exposure limits: "Exposure should be recorded as the average over the specified short-term reference period, normally 15 minutes, and should be determined by sampling over that period." So you must sample over 15 minutes and not exceed the short term exposure limit stated. And this must apply to ANY 15 minute period within the working shift.
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redken  
#6 Posted : 09 March 2010 12:24:44(UTC)
Rank: Super forum user
redken
Heather you are correct of course. The lesson to be learned is check it yourself do not rely on too hasty forum replies. http://www.hse.gov.uk/coshh/table1.pdf
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