Air pollution episode

From Glossary of Meteorology

air pollution episode

  1. An extended period of a high concentration of pollutants in the atmosphere.

  2. A public alert or notification of unhealthful air quality.

    In the U.S., the degree of alert is often based on the pollutant standards index (PSI):
    Stage 1 episode or alert, for 200 ≤ PSI < 275. Public recommendation: avoid strenuous activities. Children and elderly people advised to stay indoors.
    Stage 2 episode or alert, for 275 ≤ PSI < 400. Public recommendation: cease all physical activity, and stay indoors. Industry can be ordered to reduce emissions, and employees forced to carpool or use mass transportation for their necessary travel.
    Stage 3 episode or alert, for PSI ≥ 400. Everyone ordered to remain at home with windows closed. Minimize physical exertion and avoid driving vehicles. Automobile travel could be restricted and industries ordered to reduce emissions.