Substance with lowest smelling threshold

polysom

Well-known member
Apr 4, 2021
Today I received my Geosmin, which is said the nose can detect it up to a concentrations as low as 400 parts per trillion. So, I was wondering if this is the substance with the lowest smelling threshold or if there is a substance which can be smelled in an even lower concentration?
 

birdie

Well-known member
Dec 11, 2016
The worst smelling substance is supposed to be thioacetone. When they made a small amount in a lab outside Freiburg in 1889 people in the nearby town started to vomit and faint. It's a fun Youtube video about it.

From Wikipedia:
In 1967, Esso researchers repeated the experiment of cracking trithioacetone, at a laboratory south of Oxford, UK. They reported their experience as follows:

Recently we found ourselves with an odour problem beyond our worst expectations. During early experiments, a stopper jumped from a bottle of residues, and, although replaced at once, resulted in an immediate complaint of nausea and sickness from colleagues working in a building two hundred yards [180 m] away. Two of our chemists who had done no more than investigate the cracking of minute amounts of trithioacetone found themselves the object of hostile stares in a restaurant and suffered the humiliation of having a waitress spray the area around them with a deodorant. The odours defied the expected effects of dilution since workers in the laboratory did not find the odours intolerable ... and genuinely denied responsibility since they were working in closed systems. To convince them otherwise, they were dispersed with other observers around the laboratory, at distances up to a quarter of a mile [0.40 km], and one drop of either acetone gem-dithiol or the mother liquors from crude trithioacetone crystallisations were placed on a watch glass in a fume cupboard. The odour was detected downwind in seconds.[8]
 

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