GHG emissions associated with refrigerant usage at an airport should be based methodology established by  The Climate Registry, General Reporting Protocol 69 . The method  for computing GHG emissions from refrigerants is based on material balancing, which takes into  account the charging, operating, and disposal of refrigerants.  The Climate Registry, General  Reporting Protocol  contains a screening method to establish significance of GHG emissions and  quantification approaches to quantify GHG emissions. One can choose a quantification approach  based on data availability, purpose of quantification, and the level of accuracy required.  The screening method is intended for entities that do not own or operate a significant amount of  equipment that use HFCs or PFCs, but may own or operate  equipment that use refrigerants.  Typically the GHG emissions from these sources represent  a small percentage of an emission  inventory at an airport and thus, a screening method can be used to conservatively estimate these  emissions.  The screening approach requires data including the number of units, the type of refrigerant used,  the total refrigerant charge for each type of equipment, and the annual leakage rate. information should be available from the facility  as it is often required reported for Refrigerant  Management Plans.  The Climate Registry, General Reporting Protocol  provides default values  for equipment charge, equipment lifetime, assembly/installation emission factors, annual leakage  rate, and recycling efficiency. This approach is used only as a screening method since default  emission factors can be highly uncertain. The HFC and PFC emissions should then be adjusted to  account for GWP with a result of  CO$_{2e }$ (in metric tons). These gases have high GWP ranging  from 140 to 11,700 times that of  CO$_{2}$.  Equation C-14,  ( CO$_{2e }$ Emission Calculation for  Refrigerant Usage ), provides an example for refrigerant usage.  The quantification approach requires information on the quantity of refrigerant used to fill new  equipment during installation, the quantity of refrigerant used to service equipment, the quantity  of refrigerant recovered from retiring equipment, and the full and proper charges of new and  retiring equipment. The approach tracks emissions from equipment manufacturing, operation,  servicing, and disposal.  Equation C-14. CO$_{2e }$Emission Calculation for Refrigerant Usage  Emissions (metric tons)  =  Capacity charge x % of capacity/year + Refrigerant Added – Refrigerant  Recovered  CO$_{2e }$Emissions (metric tons) = Emissions (metric tons) x GWP  69 Climate Registry, General Reporting Protocol, Version 2.0,  Accurate, Transparent, and Consistent  Measurement of Greenhouse Gases Across North America , March 2013,  http://www.theclimateregistry.org/downloads/2013/03/TCR_GRP_Version_2.0.pdf.  73$_{ }$ APPENDIX C$_{ }$