A page on the health and environmental effects of hydrogen sulfide.

Health effects vary with how long, and at what level, you are exposed. Asthmatics may be at greater risk. Low concentrations – irritation of eyes, nose, throat, or respiratory system; effects can be delayed. Moderate concentrations – more severe eye and respiratory effects, headache, dizziness, nausea, coughing, vomiting and difficulty breathing. High concentrations – shock, convulsions, unable to breathe, coma, death; effects can be extremely rapid (within a few breaths).

(Exposure information from OSHA.gov)

Questions

Post and answer questions about the health effects of hydrogen sulfide here:

Exposure limits from various sources, from an Airgas Materials Safety Data Sheet:

ACGIH TLV (United States, 3/2016).
 STEL: 5 ppm 15 minutes.
 TWA: 1 ppm 8 hours.
NIOSH REL (United States, 10/2013).
 CEIL: 15 mg/m³ 10 minutes.
 CEIL: 10 ppm 10 minutes.
OSHA PEL 1989 (United States, 3/1989).
 STEL: 21 mg/m³ 15 minutes.
 STEL: 15 ppm 15 minutes.
 TWA: 14 mg/m³ 8 hours.
 TWA: 10 ppm 8 hours.
OSHA PEL Z2 (United States, 2/2013).
 AMP: 50 ppm 10 minutes.
 CEIL: 20 ppm

Note that these show toxicity at levels close to the ability of the wearable electronic monitors (see above) can detect -- 10-15ppm; "STEL" means Short Term Exposure Limit, or an "acceptable average exposure over a short period of time."