#Hydrogen Sulfide danger
18 messages in this thread
Doug- Olfactory paralysis from H2S inhalation is a fact. I will endeavor to
find a medical description of the mechanism involved. Regrettably, work has
severely impacted on my free time lately…seems like always…and I haven't
been able to keyboard the H2S Toxicity data I mentioned a while back. Instead,
I will be happy to photocopy it ( about 4 pages ) and mail to anyone who wants
a copy.
Since I don't have it sitting here at home, I won't try to list specific levels
(ppm) at which various physiological effects begin and possibly be in error.
Regards-
Michael
Michael,
PMFJI
I've been lurking this forum for a couple of months, but this seems like a good
place to say something. I work around the H2S somewhat regularly, have taught
the safety course required by law for oil field workers, and just completed my
annual safety certification to work in the oil fields in an H2S environment,
here are the ANSI 23Z-1972 standards:
0.0002 percent (2ppm) Obvious odor
0.001 percent (10ppm) Beginning eye irritation (OSHA 8 hour max exposure)
0.0015 percent (15 ppm) STEL (Short Term Exposure Limit)
0.01 percent (100 ppm) Coughing, eye irritation, loss of smell in 2-5min
0.02 percent (200 ppm) marked conjunctivitis, respiratory tract irritation
in 1 hour
0.05 percent (500 ppm) loss of conciousness, possible death in 30 min-1hr
0.07 percent (700 ppm) Rapid unconciousness, breathing will stop and death
will occur if not promptly rescued
0.10 percent (1000 ppm) Immediate unconciousness, early cessation of
breathing and death within minutes. Death may occur even if moved to fresh air
at once.
This is dangerous stuff. The only gas more lethal (other than some specialized
chem warfare stuff) is hydrogen cyanide (HCN). Additionally mixtures of 4.3 to
46 pervent volume in air is explosive, it burns to form sulfur dioxide
(another poisonous, but less toxic gas), and is water soluable (4 parts H2S to
1 part water at 32 degrees F).
I think it's tough for people to understand even straightforward numbers like
relative risk of dying in a car versus an airplane… Can you place those
numbers in perspective? For example, what's a common way to produce H2S, and
how much of those reactants would produce enough gas in a closed 10 x 10 room
in order to reach 0.05 percent? What's a common reaction that produces the
whiff of obvious odor?
John-
The values Jim cited are volumetric basis. A 10x10x8 ft room contains 800 cubic
feet. You would have to have 0.4 ft^3 or ~11.5 liters of 100% H2S to reach a
500 ppm concentration. This is extremely unlikely in most circumstances at
home, but is entirely possible in some mines lacking ventilation.
A far greater risk to rockhounds is entering areas of low oxygen concentration.
Hypoxic conditions can occur anywhere insufficient air circulation combines
with oxygen hungry materials such as sulfide or telluride ore bodies or high
concentrations of organic material. Several years ago, three crew members of a
Tuna fishing boat died from both H2S exposure and hypoxia when they lost
refrigeration of the fish hold and the tuna began to rot. They attempted to
remove the decomposing tuna and died when they entered the confined space.
Death was immediate.
Oil and natural gas Refining necessarily produce H2S in desulphering crude oil
or gas. H2S naturally occurs in oil and gas fields. Many natural gas plants
desulfur the natural gas using Claus process sulfur recovery. If you ever fly
over Alberta, north of Calgary are huge, and I mean huge!, blocks of sulfur
recovered from natural gas. Most refineries produce H2S as a byproduct from
crude distallation, catalytic cracking units, hydrotreating and decoking (among
others). This H2S is usually converted to elemental sulfur using Sulfur
Recovery units.
We also operate a Sulfur Recovery Unit and produce about 20 Tons/day of molten
sulfur. Someday, I intend to play around with controlled cooling of molten
sulfur to try to produce large sulfur crystals. However, sulfur is *really*
peculiar. Unlike most liquids, molten sulfur viscosity increases with
temperature to become a tarry substance, further heating then results in a drop
in viscosity. This is due to the bonding nature of sulfur. It exists as
various species, S2, S3, S4, S6, S8 and polyermic S. Forming sulfur crystals
is very dependent on initial temperature and rate of cooling. No nearly as
simple as making "rock" candy.
Michael
My experiment uses large quantities of Argon-Ethane gas. One of the worst
contaminents is H2S, and every once in a while we get a truck full of it. I
always wondered why H2S is associated with ethane. Now I know – thanks!
How large are those "blocks of sulfur"?
John – I will have to make a phone call to find out. I do not want to
exaggerate the size, nor understate it. For now, I can definitely say that
from the air, they appeared to cover about 2-3 acres and were about 40 feet
high.
Will get the facts.
Michael
John,
The most common method of producing H2S is the decay of biological material.
Hence the name "rotten egg gas". Your nose can detect down to 0.13 ppm. That's
roughly 1/8 of 100 ppm or if you want a different comparison, about 1/6 of an
inch out of 15.5 miles. Around the home, H2S can be present in sewers, rotten
garbage, compost piles, and similar settings. The most common source is
probably by "passing gas". Entire oil drilling rigs have been cleared here in
Texas because one of the roughnecks ate too much Mexican food and "broke wind"
near a sensor. (The alarms are set to trigger at 10 ppm)
I can't really think of a common reaction that would fill a 10X10 room in a
houshold setting. Mixing sulfuric acid (present in some tile cleaners), with
ammonia could produce H2S. I doubt that lethal concentrations could build up
in a home under normal circumstances, but pouring sulfuric acid down the drain
in an older home (with iron sewer pipe.) might. In laboratories, reactions of
sulfuric acid w/ other sulfur containing compounds can produce H2S. I've heard
of High Schools were one of the kids decided to make a stink bomb with FeS and
H2SO4 and the entire building was evacuated. Pouring H2SO4 down the sewers
might, and muriatic acid (used for etching tile, and in swimming pools), could
react with sulfur containing compunds to produce the same result. I'll think
some more about it.
Jim
H2S is only produced by anaerobic reactions, right? A well-maintained compost
pile shouldn't smell like that, but that's a topic for the gardening forum.
🙂
As for the 10 x 10 room, I meant what sort of household reaction would produce
dangerous levels of H2S. As you said, there are certainly situations where
household chemicals can do it.
As for human-produced H2S, are you saying that the level could approach 10
ppm?
>>As for human-produced H2S, are you saying that the level could approach 10
ppm?
Yes, The situations I know about, the sensors that triggered, and the people
that triggered them were in the cellar, which is a confined spave below the
drilling rig, where the casin on the well comes out of the ground. According
to OSHA regs you can work in a max of 10ppm for 8 hours a day, 40 hrs. per week
with no additional protection.
>>H2S is only produced by anaerobic reactions, right?
Right.
Actually, human flatulence consists primarily of methane with lesser levels of
mercaptans and much lower levels of H2S. Mercaptans are sulfur-bearing
hydrocarbons that are more often associated with skunk odor, and are used to
odorize natural gas and LPG for domestic consumption.
As an aside, intestinal gas has resulted in surgery room explosions, albeit
rarely. In our house, with 4 males, explosion is the least of our worries, and
may answer your question about how to fill a 10×10 room.
<g>
Hmm, flatulence trivia… Japanese children have flashcards to help them learn
the 50-or-so basic phonetic sounds of their syllabary. One is "fu," and the
flashcard usually shows a fat naked guy (think of a Japanese construction
worker in loincloth, or a sumo wrestler) with comic-book-like "wind lines" near
his behind.
I see to remember that a variety of mercaptan is listed in the Guinness Book of
World Records, as a smell recognizable at the lowest levels, which makes it
"smelliest" in some sense.
Jim- don't forget about the dangers of setting up a Popeil Kitchen Refinery
(not available in stores).
<G>
Jim-
Thanks for the summary of H2S toxicology. It is what I have intended to post
for some time, but haven't somehow coordinated (wonder if a busy schedule is
any factor). I work in a sulfuric acid plant that processes up to 84 tons of
H2S per day. In 37 years, we have had zero incidents involving plant
personnel. Although 28 years ago, we did experience a significant leak in a
pipeline that did kill a rabbit and three birds.
Most forum members will not be exposed to substantial risk in their normal
activities, however there are some circumstances in the field where
significant concentrations of H2S can occur:
Sulfide zones of ore deposits evolve H2S which is slighty heavier than air.
Localized areas of fatal concentrations can occur.
Coal deposits and some carbonaceous shales are another potential exposure.
Hydrothermal zones near active volcanoes or other geothermal structures. If
sulfur deposits are present, you can bet H2S was the source.
SO2 (sulfur dioxide) is less lethal than H2S at similar concentrations, yet its
PEL (permitted exposure limit) is 5 ppm or half the allowable exposure limit of
H2S. SO2 has such an irritating effect on mucosal membranes that rarely will
an individual chose to remain in exposure for long, and certainly it warns you
well before you hit a lethal level.
The toxicity of H2S is due to its chemical binding with haemoglobin forming
methaemoglobin. The oxygen carrying capacity of the circulatory system is
rapidly and significantly diminished. Fortunately, the effects are relatively
quick to reverse, provided the victim is removed to an H2S free area. There is
a marvelous training film on H2S that demonstrates the effect of H2S exposure
and subsequent recovery on a rat.
Regards-
Michael
Hi, Jim–
Welcome to the forum/section!
Thanks for the info. I am pleased to hear there is a lot of watering of the
eyes and other symptoms to drive one away before the danger gets severe,
provided one does not generate too much H2S too fast. It suggests to me I am
not being crazy when I heat a small specimen in my apartment, though I will
continue to make sure the fan is on and the windows open when I do such things.
Anyone care to figure roughly how big a specimen of sulfide ore would have to
be to endanger one's life before one could be driven out of a room by the smell
and irritation? Let's say 0 to 500 ppm in a minute is too fast, or 11
liters/minute is too fast (see Michael's post in this topic). How much sulfide
ore can make 11 liters of H2S gas (at room temperature/pressure)? Without a
ready supply of acid, and assuming there is not a lot of bisulfide in the ore,
it may be quite large.
Anyway, dripping a bit of HCl on a specimen and smelling the bubbles for H2S
cannot be producing enough unless they are _very large_ bubbles.
–Doug
Remember–from Jim's table– 1000ppm will cause immediate unconciousness.
1000ppm is equivalent to 1 milliliter(100%H2S)/liter. One shallow breath is
approximately 1 liter. So all that needs to be evolved near your snout is 1 to
2 mls of H2S to put you down. A pound of sulfide ore in acid sould provide
more than that I think. Haven't done the stoichiometry yet.
Michae
Hi, Michael–
I knew there was a reason I only heat small grains of mineral, and only put a
drop or two of acid on a specimen (besides destroying too much of the specimen,
that is). 🙂 Even that pound in acid might not generate that ml of H2S fast
enough to knock me over before it disperses a bit (assuming I do not heat the
acid), but I am not ready to bet my life on it.
–Doug