There’s a suggestion that olfactory fatigue occurs but not to the degree or as well-documented as H2S.
Here’s a tidbit I found about methyl mercaptan (http://tools.niehs.nih.gov/wetp/Public/DOE_Trainers/13_HANDOUT_SENSE_OF_SMELL.pdf)
For example, because methyl mercaptan has an odor recognition threshold of only 0.0021 ppm, it is often mixed with natural gas as an indicator of leaks. However, approximately one person in 1000 is unable to detect the strong odor of this mercaptan. Impulses travel to the olfactory bulb located at the base of the front brain. At the bulb, fibers from the nose contact other nerves, which travel on to various parts of the brain. An estimated 100 million receptor cells are present in humans. For a substance to be detected as an odor by the receptor cells, several criteria must be met:
The substance must be volatile enough to permeate the air near the sensory area.
The substance must be at least slightly water-soluble to pass through the mucous layer and to
the olfactory cells.
The substance must be lipid-soluble because olfactory cilia are composed primarily of lipid
A minimum number of odorous particles must be in contact with the receptors for a minimum length of time.
An estimated 30% of the elderly have lost the ability to perceive the minute amount of this mercaptan used in natural gas.
The current OSHA PEL is 10 ppm (ceiling). The 1998 OSHA PEL is 0.5 ppm. The ACGIH TLV and NIOSH REL is 0.5 ppm. (http://www.cdc.gov/niosh/idlh/74931.html)
I’m thinking at 0.0021 ppm odor threshold, this little newspaper tidbit still seems odd.
I did not have a lot of time to dive into the literature, but olfactory fatigue is reported for ethyl mercaptan at 4ppm. I would suspect methyl mercaptan would also have a similarly low threshold for olfactory fatigue.
Sufficient concentration of the highly stinky gas, hydrogen sulfide, will
knock out one's sense of smell. Is it possible that the same applied to its
From: DCHAS-L Discussion List [mailto:dchas-l**At_Symbol_Here**MED.CORNELL.EDU] On Behalf Of
The initial statement about the amount of Mercaptan let loose and undetected
is also at odds with common sense :
"Chemical manufacturer DuPont has reported that about 23,000 pounds of a
flammable toxic chemical escaped in the building where four of its workers
died two weeks ago at a Houston-area plant.
DuPont disclosed in a news release the quantity of the methyl mercaptan that
led to the deaths Nov. 15."
Did anyone else find this tidbit odd? How could there be methyl mercaptan
vapor build up and no one notice it? Around here, someone takes the sealed
jar out of the dessicator to take to the fume hood and there's howling up
and down the hall from the smell.
Debbie M. Decker, CCHO, ACS Fellow
Chair, Division of Chemical Health and Safety University of California,
Birkett's hypothesis: "Any chemical reaction that proceeds smoothly under
normal conditions, can proceed violently in the presence of an idiot."
SAFETY FLAWS LED TO DEADLY DUPONT LEAK
Tags: us_TX, industrial, follow-up, death, other_chemical
HOUSTON -- It was DuPont's third deadly U.S. accident in five years and the
deadliest of them all. On November 15th, a chemical leak in LaPorte took the
lives of four workers, including two brothers.
They were inside a building that manufactured insecticides.
Federal investigators have now claimed there were problems both with the
building and with how things were done there.
"What we are seeing here in this incident in LaPorte is definitely a problem
of safety culture in the corporation of DuPont," said Rafael Moure-Eraso,
Chairman of the U.S. Chemical Safety Board.
After months of investigating, the independent agency found a ventilation
system had been broken that allowed a harmful chemical called methyl
mercaptan to build up without anyone knowing it.
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