The pollutant-to-pollutant conversion factors file is required when there is a mismatch between the pollutant in the inventory and the pollutant for which the speciation profiles have been developed. The typical example is when the inventory has VOC (or ROG), but the speciation profiles are developed for TOG. SMOKE permits such a factor to be applied to any pollutant. The same format is used by all source categories.

These factors can be applied to the inventory using one of two assignment approaches: either by FIPS/SCC or by Speciation Profile ID. The same approach must be used for all sources in a single run of Spcmat. Historically in SMOKE, the FIPS/SCC approach has been used; however, starting with SMOKE version 2.3, users may instead apply these factors by Speciation Profile ID. For assignment of factors using the state/county FIPS and SCC codes, the available combinations and hierarchies for applying the factors are the same as for the speciation cross-reference (see Section 6.16, “Spcmat”), with the exception of the plant ID and other more specific source characteristics for point sources. For assignment of the factors using Speciation Profile ID, there is no assignment hierarchy - whatever profile was assigned to a source by the GSREF file will be used to choose the factor to apply from the GSCNV file, for the appropriate pollutants. To assign these factors by Speciation Profile ID, a special header line is needed, as described below. SMOKE version 2.3 is backward compatible with previous GSCNV files used with earlier versions.

The GSCNV file is not needed if there is no mismatch between the inventory and the pollutants in the speciation profiles file. The Spcmat program will input and use this file only when the POLLUTANT_CONVERSION environment variable is set to Y.

If emissions types (emission process/pollutant combinations) are being used, as with mobile source processing using the Emisfac program (see Section 2.8.4.5, “Emission processes”), the emission type must be listed instead of the pollutant. For example, if exhaust running VOC emissions were being converted to exhaust TOG, then EXR__VOC and EXR__TOG would need to appear in their respective columns on the header line (line 1 in the "old" format below or in the first and second columns in the "new" format). It would not be correct to put only VOC and TOG. All emission types must be listed, or the conversion factor that will be applied is 1. This approach permits conversion factors that are specific to each emission process (e.g., different conversions for EXR and EXS).

The "old" format of the GSCNV file for FIPS/SCC assignments is shown in Table 8.63, “Old format for GSCNV (using FIPS/SCC assignments)”.

The "new" format of the GSCNV file for Speciation Profile ID assignments is shown in Table 8.64, “New format for GSCNV (using Speciation Profile ID assignments)”. The new format is consistent with the format created by the Emission Modeling Framework Speciation Tool.