# Estimating amount of Hydrogen Sulfide released into the air? and how fast does gas expand when it is produced?

I unknowingly exposed myself to hydrogen sulfide gas and am trying to figure out how much Hydrogen Sulfide gas i may have been exposed to.

I mixed .5 grams of Sodium Sulfide Nonahydrate into a solution containing excess acid (NH4+) as shown below. So I expect all of the Sodium Sulfide to react to form Hydrogen Sulfide.

KH2PO4  0.4
NA2HPO4 0.53
NH4CL   4.0
Na2S.9H2O   0.5

100mL water


If all the Na2S.9H2O reacts , then 70.83mg of Hydrogen Sulfide are produced.

At room temperature and one atmosphere (inside of a small room say a studio sized room), is there any way to estimate how much exposure I received? in terms of PPM given how much Hydrogen Sulfide was produced?

I immediately smelled rotten eggs and then the smell went away after a second. Is this because I inhaled so much? Or because it dissipated so quickly?

That Hydrogen Sulfide is heavy also complicates things (does it not spread as easily? would it settle around me instead of spreading all around the room?)

To add, this paper shows that most of the hydrogen sulfide is released from solution amost immediately in HEPES buffer, so I wonder if it would be the same here, and what that means for exposure (did i just breath in most of the hydrogen sulfide at once, or did it spread out into the air so fast i did not breath much in?) https://www.sciencedirect.com/science/article/pii/S0003269711006695?via%3Dihub

"A preweighed crystal was dropped into an open 150-ml beaker containing 100 ml of
Hepes buffer (arrow). The solution was mixed with a magnetic stir bar, and H2S
was recorded with the H2S sensor. More than 80% of the H2S was formed during the
first 10 s, essentially as fast as the crystals was dissolved, and H2S
concentration subsequently declined due to volatilization. Panels A and B are
from the same experiment with different time scales."

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• H2S Is known to affect human smelling so it is not being noticed later even in high concentration. – Poutnik Jul 16 '20 at 11:45