0.00047 ppm is the recognition threshold, the concentration at which 50% of humans can detect the characteristic odor of hydrogen sulfide,[12] normally described as resembling "a rotten egg".
Less than 10 ppm has an exposure limit of 8 hours per day. 1020 ppm is the borderline concentration for eye irritation.
50100 ppm leads to eye damage.
At 100150 ppm the olfactory nerve is paralyzed after a few inhalations, and the sense of smell disappears, often together with awareness of danger.[13][14]
320530 ppm leads to pulmonary edema with the possibility of death.
5301000 ppm causes strong stimulation of the central nervous system and rapid breathing, leading to loss of breathing.
800 ppm is the lethal concentration for 50% of humans for 5 minutes exposure (LC50).
Concentrations over 1000 ppm cause immediate collapse with loss of breathing, even after inhalation of a single breath.
Nasty stuff, not to mess with, but seldom found in high enough concentrations to kill you outside of enclosed spaces, gas plants, and (sour) oil production locations. In an airspace as large as the Gulf, it is highly unlikely that there is sufficient H2S in any offshore well to present a hazard to anyone on land. The H2S if present will dissipate before the oil gets to shore.
The EPA has stated on their site that there is enough to cause eye irritation, nausea and headache along with a ‘rotten egg’ smell.
I will try to find the link on the PPM.