Neal,
When did we get back to the old John Denver song, about the "Dead Skunk i
n the Middle of the Road, Stinkin' to High Heaven?"
If I remember correctly, it was a very bad guitar lick in G Major
(done it in D major as well) and the song (music and lyrics) stinks just ab
out as bad as the skunk. Played guitars all over the world and stil
l own 3.
There ain't nobody who doesn't have anosmia (the inability to smell) who ca
n miss a dead skunk, and even if you have, when that particular sulfur-
containing miasma comes in, it'll still make your eyes smart and your sin
uses contract. However, while I've know some dogs and people (mys
elf included) to be quite unhappy about a skunk contact, I've never yet s
een one to die of it. Unless, of course you were trying unsuccess
fully to drag it out of the highway and got run over by a truck. Mi
ssed that one.
If this is about how little does it take, consider the old one about how
sensitive a dog's nose is to a drop of ammonia or chlorine in 100,000 gal
lons of water. If I remember right, this is still true. A
nd you and I would generally consider this was just a way to render the wat
er potable or fit to swim in (perhaps not even enough if it were chlorine o
r a chlorine-active compound? - just don't add certain other reactive chemi
cals such as bleach).
Are we just back to the "if it smells bad it must be toxic?" issue (
often untrue) (let your mother cook cabbage when you're downstairs playing
with your chemistry set in the old days when nearly everything had some sul
fur it it; guess which one smelled worse?) I'd bet on the cabbage
.
What I missed was where this was going and why you needed it. We al
l know that "odor thresholds" are just plain garbage for determining airbor
ne "safe" chemical levels. Consider all the H2S issues. The
smell goes away because of olfactory fatigue, you stay in exposure becau
se if you can't smell it anymore, so it must be gone (around 250 ppm),
and die of delayed onset pulmonary edema. There are things that sti
nk to high heaven (such as mercaptans added to propane or LPG/natural gas)
that are not toxic in themselves at the added concentrations but that will
drive nearly anybody outdoors to seek safety in fresh air because of the ov
erwhelming stench). Where the stench is not the problem, but the
potential flammable/asphyxiant issues ARE. Meaning, its a good th
ing to get out of flammable gas exposures, if only driven out because of
a relatively non-toxic stench.
How many ppm are there in a haystack, and how many ppm does the average n
eedle have? Measure an average needle against an average length of
hay (A/B) (use calipers and a measuring tape). You could actually d
o this in a courtroom. Estimate how many such average lengths of ha
y there are in a haystack (C) (pull out say 100 samples and just use a tape
measure) and then do a mass/ratio calculation based on the 3 dimensions of
the haystack which could easily be determined with a surveyors tape measur
e and a stepladder (D). Determine a ratio of A/B, and 
;divide by C/D: the result is left as an exercise for the student
. I'd suggest it would be in the ppb range if not the ppt range.
Or to suggest an old movie with a bad plot about Cheyenne Mountain:
"Wouldn't you rather play a nice game of chess?"
Alan
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