Cardiovascular Emergencies Test No. 3 From Paramedic Emergency Care 3rd Edition Progress Indicator: Question 3 of 20 3.  What is the origin of hydrogen sulfide? Choices: It is liberated by old timbers. It is liberated by burning explosives containing sulfur such as black powder or dynamite. It is liberated from pools of stagnant water in the mine. It is liberated when the methane content of air reaches five (5%0 percent or above.