content_image/552411.jpg content_image/552409.jpg
For this example, and as shown in Table B-5 ( Conversion Factors ), the THC to TOG conversion factor is 1.16. Therefore, the amount of TOG emitted by the A320 aircraft is an estimated 322 kilograms (or 278 kilograms times 1.16). 

To speciate the TOG emissions, the HAP speciation profile (i.e., the percentage of emissions associated with a particular HAP) is obtained. To then derive the emission rates for an individual HAP, the mass fraction profile is multiplied by the total amount of TOG emission. The calculation for obtaining the estimated emission rate for an individual HAP (i.e., benzene, formaldehyde) is provided in Equation B-4 ( Aircraft HAP Emissions Using TOG ). 

Where: 

<img src='content_image/552411.jpg'>

i = HAP of interest 

For demonstration purposes, Table B-6 ( Example HAP Emission Estimates ) provides the emission estimate for the A320 aircraft example for three individual HAPs. As shown, computed emission totals for ethylene, formaldehyde, and toluene emissions are approximately 43, 34, and 2 kilograms, respectively. 

<img src='content_image/552409.jpg'>

Source: Recommended Best Practice for Quantifying Speciated Organic Gas Emissions from Aircraft Equipped with Turbofan, Turbojet, and Turboprop Engines , May 27, 2009, http://www.epa.gov/otaq/regs/nonroad/aviation/420r09901.pdf. 

## B.2.2 Auxiliary Power Units 

For large commercial and cargo aircraft, APUs generate on-board electricity and air conditioning (A/C) while an airplane is taxiing or parked at the gate. In some cases, GPUs are used. APUs and GPUs are traditionally powered with jet fuel and diesel fuel, respectively. At many airports, gate furnished electricity and air conditioning are used to supplement and/or replace usage of APUs/GPUs. 

## B.2.2.1 Methodology 

With one exception, the procedure for calculating HAP emissions for an APU is the same as the procedure used to compute HAP emissions for an aircraft eng ine, described in the previous section. For APUs however, the amount of fuel consumed is based on the run time of an APU 

