The declaration of episode stages shall be in accordance with the following criteria:

(1) Stage: "First or forecast" - the forecast stage indicates the presence of meteorological conditions conducive to the accumulation of air contaminants. A forecast stage may be declared when an air stagnation advisory is issued by the national weather service or there is equivalent indication of stagnant atmospheric conditions and conditions are forecast to persist for 24 hours. Declaration of this stage will activate increased air quality surveillance.

(2) Stage: "Second or alert" - the alert stage is that concentration of pollutants at which control actions are to begin. An alert will be declared when any one of the following levels is reached:

(a) SO2 - 800 µg/m3 (0.3 ppm), 24-hour average.

(b) PM-10 - 350 µg/m3, 24-hour average.

(c) CO - 17 mg/m3 (15 ppm), 8-hour average.

(d) Oxidant (O3) - 400 µg/m3 (0.2 ppm) - 1-hour average.

(e) NO2 - 1130 µg/m3 (0.6 ppm) 1-hour average, 282 µg/m3 (0.15 ppm) 24-hour average; and meteorological conditions are such that the pollutant concentrations can be expected to remain at or above the alert levels for 12 or more hours or can be expected to recur within 24 hours unless control actions are taken.

(3) Stage: "Third or warning" - the warning stage indicates that air quality is continuing to degrade and that additional control actions are necessary. A warning will be declared when any one of the following levels is reached:

(a) SO2 - 1,600 µg/m3 (0.6 ppm), 24-hour average.

(b) PM-10 - 420 µg/m3, 24-hour average.

(c) CO - 34 mg/m3 (30 ppm), 8-hour average.

(d) Oxidant (O3) - 800 µg/m3 (0.4 ppm), 1-hour average.

(e) NO2 - 2,260 µg/m3 (1.2 ppm), 1-hour average; 565 µg/m3 (0.3 ppm), 24-hour average; and meteorological conditions are such that pollutant concentrations can be expected to remain at or above the warning levels for 12 or more hours or can be expected to recur within 24 hours unless control actions are taken.

(4) Stage: "Fourth or emergency" - the emergency stage indicates that air quality is continuing to degrade toward a level of significant harm to the health of persons and that the most stringent control actions are necessary. An emergency will be declared when any one of the following levels is reached at any monitoring site:

(a) SO2 - 2,100 µg/m3 (0.8 ppm), 24-hour average.

(b) PM-10 - 500 µg/m3, 24-hour average.

(c) CO - 46 mg/m3 (40 ppm), 8-hour average.

(d) Oxidant (O3) - 1,200 µg/m3, (0.6 ppm), 1-hour average.

(e) NO2 - 3,000 µg/m3 (1.6 ppm), 1-hour average; 750 µg/m3 (0.4 ppm), 24-hour average; and meteorological conditions are such that this condition can be expected to remain at or above emergency levels for 12 or more hours, or can be expected to recur within 24 hours.

(5) Stage: "Termination" - once declared, any stage reached by applying these criteria will remain in effect until the criteria for that level are no longer met. At that time, the next lower stage will be declared. When conditions improve to where the criteria are no longer met for any episode stage, the episode will be terminated.