At what AQI level should longer, passive activities (such as prolonged instruction) be moved indoors? (TK-12; Childcare Programs) The Centers for Disease Control and Prevention (CDC) and Environmental Protection Agency (EPA) recommend that unusually sensitive people consider reducing prolonged or heavy exertion when the Air Quality Index (AQI) is between 51-100 and that all children and teenagers reduce prolonged or heavy exertion when the AQI is above 100.