APPENDIX A5$_{ }$ Tank Type 1  Evaporative Emission Losses  openings and because fuel clings to the tank walls as the liquid level and roof are lowered. $^{4 }$Domed external floating roof tanks usually result from retrofitting an external floating roof tank with a fixed roof.  E$_{HC }$= EB + EW  Where:  E$_{HC }$= total hydrocarbon emissions from a single tank over a given time period.  EB = breathing emissions from the tank.  EW = working emissions from the tank.  A5.3.1.1  Methodology  Equation A5-9. Evaporative Emissions for Storage Tanks  Data Inputs  Description  Source  Tank Type  Refer  to  Table  A5-3  ( Evaporative  Emission Losses of Fuel Storage Tanks ).  Information may be obtained from the airport  operator,  fueling  contractor,  or  by  visual  inspection of the tank(s).  Tank Dimensions  Tank dimensions (e.g., shell diameter, and  height) are necessary to calculate emission  losses.  Information may be obtained from the airport  operator,  fueling  contractor,  or  by  visual  inspection of the tank(s).  Fuel Type  Specification of the type of fuel stored in  Information is given in Section 7.1,  Organic  Table A5-4. Data Inputs for Fuel Storage Tanks  Evaporative emissions from fuel storage tanks at airports can be estimated using FAA’s  EDMS/AEDT or EPA’s TANKS program. Both models are based  on the emission estimation  procedures detailed in Chapter 7,  Liquid Storage Tanks,  of EPA's  AP-42 28 .  The general methodology for calculating storage tank evaporative emissions is expressed by  Equation A5-9  ( Evaporative Emissions for Storage Tanks ).  The methodologies for calculating breathing emissions and working e missions is different for  each tank type (e.g., fixed, horizontal, floating, etc.) and is dependent on  data inputs, such as  physical tank dimensions, fuel type being stored, meteorological data, fuel throughput, and other  tank-specific characteristics that are further detailed in Chapter 7.1,  Organic Liquid Storage  Tanks 29 , of EPA’s AP-42. An overview of these data inputs and the likely sources of obtaining  this information are given in  Table A5-4  ( Data Inputs for Fuel Storage Tanks ).  28  EPA, AP-42, Chapter 7,  Organic Liquid Storage Tanks,  http://www.epa.gov/ttnchie1/ap42/ch07/.  29  EPA, AP-42, Chapter 7.1,  Organic Liquid Storage Tanks ,  http://www.epa.gov/ttn/chief/ap42/ch07/final/c07s01.pdf.  33$_{ }$