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type, and correcting fo r the reduction of pollutants by any air pollution control equipment in operation. 

In addition, the SO$_{2 }$emission factors are reflective of the fuel sulfur content of the fuel, which may be obtained from the fuel supplier and/or the airport operator . PM emission factors are reflective of the fuel ash content of the fuel. This may be obtained from the fuel supplier, airport operator, or may be taken from calculation of default ash content of fuels as described in Chapter 1.3, Fuel Oil Combustion of EPA’s AP-42 21 . 

The methodology for obtaining the appropriate emission factors is expressed by Equation A5-2 ( Emission Factors for Boilers and Heaters ). 

Where: 

EF = emission factor of pollutant (i.e., CO, SO$_{2}$, PM$_{10}$, PM$_{2.5}$, NO$_{x}$, or VOC), expressed in pounds per thousand gallons (for liquid fuels), million cubic feet (for natural gas), or ton of fuel (for coal). 

<img src='content_image/583732.jpg'>

UEF = uncontrolled emission factor of pollutant, expressed in pounds per thousand gallons (for liquid fuels), million cubic feet (for natural gas), or ton of fuel (for coal). 

CF = air pollution control factor, expressed as a percentage. 

FM = fuel modifier (fuel weight percent sulfur for SO$_{2 }$ emission factor; fuel weight percent ash for PM emission factor; ignore for other pollutants). 

## A5.2.2 Generators 

Generators at airports typically are fixed in place and located throughout the airport to provide supplementary or emergency power. These generators are likely powered by gasoline or diesel - fueled reciprocating internal combustion engines. 

## A5.2.2.1 Methodology 

There are two methodologies to calculate emissions from generators: (i) EPA’s AP-42 method, which calculates emissions based on the capacity rating (in horsepower) of generator engines, and (ii) the U.S. Air Force’s method, which calculates emissions based on the amount of fuel consumed. 

Data inputs required for the emissions calculation for both met hodologies (e.g., capacity of generator engine, time of gene rator usage, type and quantity of fuel burned, and air pollution control factor) for each generator should be obtained from the airport operator, the equipment manufacturer, and/or the fuel supplier. 

