Aviation Emissions and Air Quality Handbook  should be considered as these variables factor into the frequency and duration with which an  APU is operated (see  Appendix A2 ,  Auxiliary Power Units Emission Inventory for Criteria  Pollutants ).  Currently, EDMS/AEDT can estimate criteria pollutant emissions from the following stationary  sources of air emissions, categorized based on whether the emissions occur from fuel combustion  or from passive, non-combustion processes such as evaporation or erosion:  For combustion-related stationary sources, activity levels in the form of an operating schedule  (e.g., annual hours of operation) or a mass of fuel consumed (e.g., annual  cubic feet of natural  gas) are factored against appropriate emissions factors to derive an emissions inventory. For non- combustion sources, the activity levels required for an emissions calculation relate to a number  of factors including (but not limited to) the level of material or fuel moved through or stored  within the device, the dimensions and size of the device, and the application area over which a  substance is applied.  Appendix A5  ( Stationary Sources Emission Inventory for Criteria Pollutants ) contains detailed  data input requirements and calculation steps used to compute emissions from all combustion and non-combustion stationary sources identified in this section.  Motor vehicle criteria pollutant emissions inventories typically focus on three distinct types of  activities: (i) vehicles traversing airport roadways; (ii) vehicles accessing parking facilities; and  (iii) vehicles accessing the terminal curbside areas for passenger pickup and drop-off.  The EPA’s Motor Vehicle Emissions Simulator (MOVES) is the current federally-approved tool  to compute motor vehicle emissions rates representative of the types of activities specified  above. Using locally developed data on vehicle types, fuel types, vehicle ages, inspection and  maintenance programs and other factors, MOVES will gener ate emissions rates in grams of  pollutant per vehicle mile of travel (g/VMT) or grams per vehicle hour of operation (g/hour)  against which airport motor vehicle activities can be applied. See  Appendix A4 ( Ground Access  Vehicle Emission Inventory for Criter ia Pollutants ) and  Appendix E  ( Roadway Dispersion  Modeling [Hot-Spot Analysis] ) for further details on how best to execute the MOVES for  specific applications.  In order to utilize MOVES emission rate information to estimate roadway emissions, a total  VMT must first be calculated for each type of vehicle using the airport (e.g., separate VMT for  all passenger cars, all diesel shuttles, CNG buses, etc.), which is a function of the traffic volumes  for a given type of vehicle and its travel distance. By factori ng a vehicle type’s VMT against its  corresponding emissions factor in g/VMT, a total mass of pollutant is obtained.  Travel-based VMT must also be computed for parking and curbside activities and converted to a  total mass of pollutant(s). However, the majority of the motor vehicle emissions attributable to  41$_{ }$ Stationary Sources  Ground Access Vehicles  • Combustion Sources - Boilers and heaters, generators, snowmelters, incinerators, fire  training facilities, and aircraft engine testing; and  • Non-Combustion Sources - Fuel storage tanks, cooling towers, coating and  painting  operations, de-icing and anti-icing operations, solvent degreasing, and salt and sand piles. 