Initial treatment of hydrogen sulfide exposure requires immediate removal of the victim from the contaminated area into a ventilated/fresh-air environment. Emergency responders must take hazardous materials precautions to avoid exposure to the gas; recommendations on recognizing and responding to chemical suicides are available from Chemical Hazards Emergency Medical Management.  Precautions include using respirator devices (self-contained breathing apparatus [SCBA]).
In severe cases, intubation may be necessary for ventilatory support and airway protection. Establish intravenous (IV) access or initiate other initial supportive care as necessary. Search the patient's pockets for discolored copper coins, which can be an early diagnostic clue.
In the emergency department, high-flow (100%) oxygen is the mainstay of therapy for hydrogen sulfide poisoning. Supportive therapy includes aggressive ventilation and possible use of positive pressure ventilation for the patients with evidence of acute lung injury.
IV fluids and vasopressors should be administered to hypotensive patients. Correction of acidosis based on arterial blood gas and serum lactate values is indicated.
Based on the similarities in cyanide and hydrogen sulfide toxicity, induced methemoglobinemia may be used in hydrogen sulfide toxicity. Methemoglobin acts as a scavenger, and it has a stronger affinity to hydrogen sulfide than to cytochrome oxidase. Administer 10 mL of 3% sodium nitrite IV over 2-4 minutes (adult dose). Obtain a methemoglobin level 30 minutes after administration of antidote. However, there is a lack of research evidence supporting efficacy. 
Patients who have suffered significant exposure (ie, anything other than chronic low-level exposure with mucous membrane irritation) should be admitted to the intensive care unit. Patients who are unresponsive to intravenous nitrites or who have persistent or delayed neurologic sequelae should be considered for hyperbaric oxygen therapy (HBO). Anecdotal reports indicate a salutary effect. All patients should be discussed with the local poison center and/or a medical toxicologist.