The Maryland Department of the Environment (MDEP) is responsible for air quality programs in Maryland. Maryland is in compliance with National Ambient Air Quality Standards (NAAQS) for four of the six criteria pollutants but is continuing to comply with federal standards for ozone and sulfur dioxide. Additionally, as part of the Ozone Transport Region (OTR) all counties are required to offset their NOx and VOC emissions if the facilities exceed the state thresholds listed below for these pollutants.

Some counties (e.g. Baltimore) are nonattainment and have a lower PTE threshold than OTR. In Maryland a major new source or a major modification at an existing major source planned in a nonattainment area must obtain emission offsets as a condition for approval. These offsets must (1) offset the emissions increase from the new source or modification and (2) provide a net air quality benefit. Sources must obtain ERCs if they emit more than:

Nonattainment thresholds

  • 25 tpy of NOx
  • 25 tpy VOC

OTR thresholds

  • 40 tpy of NOx
  •  50 tpy of VOC
  • 40 tpy of SO2

In Maryland the current offset ratio for nonattainment areas is 1.3 to 1 tons of ERCs to each new ton of emissions. For OTR areas, the offset ratio is 1.15 to 1 tons of ERCs to each new ton of emissions.