General population should reduce vigorous outdoor activity. Elderly and persons with existing heart or lung disease should stay indoors and reduce physical activity. General population should avoid vigorous outdoor activity. Over 300 Hazardous Early onset of certain diseases in addition to significant aggravation of symptoms and decreased exercise tolerance in healthy persons. At PSI levels above 400, premature death of ill and elderly persons may result.
Healthy people experience adverse symptoms that affect normal activity.
Elderly and persons with existing diseases should stay indoors and avoid physical exertion. At PSI levels above 400, general population should avoid outdoor activity. All people should remain indoors, keeping windows and doors closed, and minimize physical exertion. Several metropolitan areas in the U.S. have more severe air pollution problems, and may often experience PSI levels in excess of 100. However, even in these areas, PSI reading in excess of 200 are quite rare.