🔍 Key Concepts

• Hydrogen sulfide (H2S) toxicity at low, moderate, and very high concentrations • How H2S affects the nervous system and respiratory system • Difference between irritation symptoms (eyes, dizziness) and life‑threatening effects

💭 Think About

• Which option best matches what happens at very high H2S concentrations, not mild exposure? • Think about which body system failure would be most rapidly fatal if it occurred suddenly. • Which symptoms (dizziness, eye irritation, muscle contractions, breathing paralysis) are usually seen earlier versus at extreme exposure levels?

✅ Before You Answer

• Identify which choice describes a direct, immediate threat to life rather than discomfort or early warning signs. • Separate irritant effects (like on the eyes) from system shutdown effects. • Recall that at very high H2S levels, victims may collapse suddenly with little or no warning symptoms. Which option fits that?