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General Conformity

De Minimis Levels

40 CFR 93 § 153 defines de minimis levels, that is, the minimum threshold for which a conformity determination must be performed, for various criteria pollutants in various areas. The information is summarized here:

Pollutant Area Type Tons/Year
Ozone (VOC or NOx) Serious nonattainment
50
Severe nonattainment
25
Extreme nonattainment
10
Other areas outside an ozone transport region
100
Ozone (NOx) Marginal and moderate nonattainment inside an ozone transport region
100
Maintenance
100
Ozone (VOC) Marginal and moderate nonattainment inside an ozone transport region
50
Maintenance within an ozone transport region
50
Maintenance outside an ozone transport region
100
Carbon monoxide, SO2 and NO2 All nonattainment & maintenance
100
PM-10 Serious nonattainment
70
Moderate nonattainment and maintenance
100
PM2.5
Direct emissions, SO2, NOx (unless determined not to be a significant precursor), VOC or ammonia (if determined to be significant precursors)
All nonattainment & maintenance
100
Lead (Pb) All nonattainment & maintenance
25

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