🔍 Key Concepts

• Hydrogen sulfide (H₂S) toxicity increases rapidly with concentration • Difference between short-term exposure (immediately dangerous) and regular/occupational exposure limits • Typical regulatory limits use parts per million (ppm) for gases in air

💭 Think About

• Think about which level would reasonably allow workers to be exposed day after day without adverse effects, not just for a brief emergency period • Recall that as H₂S concentration rises, symptoms progress from mild irritation to serious lung and nervous system effects—what range is still considered ‘safe’ for ongoing exposure? • Compare the choices with what you know about other toxic gases’ occupational exposure limits—are regular limits usually closer to 10 ppm, 40 ppm, or 80 ppm?

✅ Before You Answer

• Confirm which of these values is closest to the commonly accepted occupational exposure limit (OEL) for H₂S for an 8‑hour workday • Eliminate any values that would more likely correspond to short-term exposure or immediately dangerous levels rather than routine exposure • Make sure the value you select is one that safety standards would consider acceptable for continuous or repeated daily exposure without expected harm