Lethal sulphur dioxide (SO₂) concentrations in air At about what SO₂ concentration (ppm) can death occur after short exposure in severely polluted air scenarios?

Introduction / Context: Sulphur dioxide is a strong respiratory irritant. Acute exposure to very high concentrations can be life-threatening. Engineers should understand approximate fatality thresholds to evaluate hazard scenarios like accidental releases.

Given Data / Assumptions:

• Units are ppm in air.
• “Death may occur” refers to short-term, high-level exposure in the absence of rapid evacuation.

Concept / Approach: SO₂ causes bronchoconstriction, airway inflammation, and pulmonary edema at high concentrations. Historical toxicology references cite lethality risk in the several-hundred ppm range for short exposure. Therefore, 400 ppm is the representative single-choice value used in many environmental engineering MCQs.

Step-by-Step Solution:

Verification / Alternative check: Emergency response guides and classical toxicology tables indicate rapidly increasing danger moving from 200 to 500+ ppm; 400 ppm is a standard “danger of death” benchmark for didactic purposes.

Why Other Options Are Wrong:

Common Pitfalls: Confusing occupational short-term exposure limits (STELs) with acute lethality thresholds; the latter are much higher.

Final Answer: 400