The Spcmat program controls the order of the species in the output files. The order does not matter to any of the AQMs that SMOKE supports, so there is not very much user control of the order. Spcmat arranges the output species first by the order in which their associated pollutants appear in the inventory table (INVTABLE) file, and next in alphabetical order. For example, if an inventory included CO, NO_x, and VOC, the CO species from the CO pollutant would be first, followed by the NO and NO₂ species for NO_x. After that, all of the VOC species would be output in alphabetical order (e.g., ALD2, ETH, FORM, ISOP, NR, OLE, PAR, TOL, XYL). If two pollutants create the same species, the first pollutant in the INVTABLE file with which the species is associated will determine its output order.