Symptoms at Various Concentrations

0.0047 ppm is the recognition threshold, the concentration at which 50% of humans can detect the characteristic odor of
hydrogen sulfide,normally described as resembling “a rotten egg”. (Well below Gas Badge detection level.)

 10-20 ppm is the borderline concentration for eye irritation. (Above the Gas Badge detection level.)

 50-100 ppm leads to eye damage.

 At 150-250 ppm the olfactory nerve is paralyzed after a few inhalations, and the sense of smell disappears, often together
with awareness of danger

 320-530 ppm leads to pulmonary edema with the possibility of death.

 530-1000 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).

 1000 ppm > cause immediate collapse with loss of breathing, even after inhalation of a single breath.

Note the huge difference between smell (.0047 ppm) and irritation (10-20 ppm) etc
.