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the equipment manufacturer. Information on fuel composition (i.e., sulfur and ash content) may be obtained from the fuel supplier. 

## A5.2.1.1 Methodology 

Emissions from boilers and heaters are estimated based on the amount and type of fuel burned by those sources over the time period being analyzed. Emissions for each pollutant are calculated by multiplying the fuel consumption rate by the emission factor specific to each pollutant. This technique is repeated for each boiler or heater in order to obtain total emissions for these stationary combustion sources. 

Total pollutant emissions from boilers and heaters may be estimated by applying Equation A5-1 ( Total Pollutant Emissions for Boilers and Heaters ). 

Where: 

E = total emissions of pollutant from the stationary source for a given time period, expressed in pounds. 

<img src='content_image/573446.jpg'>

F = total amount of fuel consumption for a given time period; liquid fuels should be expressed in terms of thousand gallons, natural gas as million cubic feet, and coal as tons. 

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). 

## Equation A5-1. Total Pollutant Emissions for Boilers and Heaters 

As shown in Equation A5-1 ( Total Pollutant Emissions for Boilers and Heaters ), the total fuel consumption is multiplied by the emission factor to estimate emissions from the boiler or heater. The accuracy of this methodology depends upon the ability to determine an appropriate emission factor for each pollutant. The following section describes how to obtain EPA-approved emission factors for each combustion source. 

## A5.2.1.2 Emission Factors 

EPA provides emission factors for a wide range of boilers, but provides little emission information specific to heaters. Therefore, for the purpose of airport emissions inventories it can be assumed that the emission factors provided for boilers are applicable to heaters of a comparable size and fuel type. 

Emission factors for most stationary combustion sources found at airports are found within Chapter 1, External Combustion Sources, of EPA’s Compilation of Air Pollution Emissions Factors (i.e., AP-42) 20 . These emission factors take into consideration several elements that have a significant impact on pollutant emissions, including: fuel type, fuel sulfur content, fuel ash content, boiler size, boiler type, and pollution control equipment. The emission factors calculated by obtaining the uncontrolled emission factor based on fuel type, boiler size and boiler 

