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 ). 

## Stationary Sources 

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: 

• 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. 

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. 

## Ground Access Vehicles 

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 

