Reactivity controls have been included in SMOKE to allow users to examine what happens to the air quality modeling results when the chemical mixture of the emissions is changed to reduce its ozone-forming potential. Examining the effect of reactivity controls is known as “reactivity assessment”. The implementation of this type of control includes permitting users to reset the base-year emissions, reset the SCC, and reset the chemical speciation profile. The controls can be applied to all sources that match an SCC or a specific facility or process within a facility.

Several issues are important when addressing emissions processing requirements for reactivity assessments. Reactivity assessment involves replacing one compound in the inventory by another compound. This replacement can impact emission projections, the total magnitude of the inventory pollutants, and the associated SCCs. The market penetration of the replacement compound may vary in time and space, which affects the future-year emissions. Also, the replacement compound may be needed in much greater or much smaller amounts, thereby affecting the total inventory emissions. Finally, if a different process is required in order for a source to use the different compound, the SCC for that source may change.

The scale of the reactivity assessment is important; it could be local, statewide, or national. A local case could involve investigating reactivity for one source. A statewide case could be implementing a change in compound based on reactivity considerations for a State Implementation Plan (SIP), and this would affect sources across the state. A national case could involve an EPA investigation of the formulation of nationally distributed consumer products.

In addition, exemptions from controls for certain sources must be permitted as part of an emissions control strategy. These exemptions can occur when a reactivity assessment determines that certain compounds and/or processes do not significantly affect pollution formation.

To address these issues, SMOKE is able to target changes in a VOC for specific classes of VOC emissions, and address the spatial and temporal considerations implied by market penetration issues. Furthermore, when replacement options are being investigated, the correct replacement operations are facilitated by SMOKE. These operations include selecting sources, changing underlying pollutant emissions, changing SCCs, correctly projecting future-year emissions based in part on market penetration issues, and appropriately speciating emissions for the new compound.

For a single run of Cntlmat, reactivity controls can be applied to only one pollutant, typically a VOC pollutant. Therefore, if you have more than one VOC pollutant in the inventory (e.g., a toxics VOC and a particulate pollutant), then separate reactivity matrices will need to be created for each pollutant that receives reactivity controls, and these controls will need to be applied in separate SMOKE runs (see Section 2.14.7, “Using Smkmerge to apply the multiplicative and/or reactivity control matrices” for more information).