Originally Posted by
Agaricus bisporus
This week's Flight international quotes a maximum allowable ash concentration of 10e-16g/cuM (That's ten to the minus seventeen). This was reduced to 10e-16 to allow flying to resume.
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Shurely shome mishtake?
(and I hope it isn't my maths)
Standing by to be corrected!
Your math looks ok but i think the starting numbers are out. Could be a misprint in the exponent (eg. e-6 vs e-16) or units - cubic cm / cubic M / cubic mm would all make rather a lot of difference.
A link to the flight article, if it's online, would be good (my quick search hasn't turned it up).
A couple of things don't tally:
1. the "previous" limit has always been referred to as "zero" - not any particular density. Elsewhere in the world this is apparently treated as "zero visible", in Europe as "zero detectable / zero predicted by model" - the latter obviously being a moving target that doesn't make sense. 10e-17g may be the current limit of detectablity I guess.
2. other reports have the
new limit at 2000 ug/cuM (micrograms / cubic metre), with no risk below 200, precautions between 200 and 2000 and no flight above 2000. Measured levels over the UK apparently never exceeded 100.
Those new levels are way off what you have quoted from Flight - I suspect they've just completely misprinted a number somewhere.