Based on the LEED Energy Modeling Protocol (EMP), and our results using the LEED Calculator.xls, the use of CO2 monitoring systems provides one (1) point under the \'Indoor Environmental Quality\' Credit 1. Demand controlled outdoor air based on CO2 levels is incorporated on this project and this credit interpretation, is to obtain approval for the resulting energy saving, under the \'Energy and Atmosphere Credit 1 - Optimize Energy Performance Category\'. We believe that a similar Credit Inquiry request was submitted under Inquiry ID Number 0050-EAc11-071001 which ruled "An engineering narrative must provide a theoretical basis and describe the expected interactive modes the measure will have with other systems of the basic simulation, and it shall describe all of the assumptions in the analog system model used to predict the savings. Advanced approval (prior to Application) of the proposed analog model and the predicted savings through this Credit Interpretation Request process is suggested." This response was not explicit and thus we are following through with the following request for credit interpretation. In support of this application we have computed energy savings using the LEED EMP. The air handling systems for the West Chevron Expansion at the Vancouver International Airport must be capable of providing substantial quantities of outdoor/ventilation air for the many passengers and staff during peak occupancy periods. Throughout most of the year and for many hours during every day, the occupancy levels will be only a fraction of the peak volume. It is proposed that multiple CO2 sensors will be installed throughout the airports public spaces. Feed back from these sensors will vary the volume of outdoor air supplied by the modular air handling units through the Building Management Controls system to maintain air quality as per ASHRAE Std 62.1999 regardless of the number of people in the terminal. This methodology will reduce energy consumption substantially particularly during the winter, and prolong the life of both particulate and gaseous absorption filters installed in each unit. Airline scheduling of the gate operations will also be factored into the Building Management Systems controls sequence to permit reinstating higher ventilation rates just prior to increased occupancy levels. Using the LEED EMP guidelines, the Design Energy Cost (DEC) for the proposed building with CO2 based demand controlled outdoor air is $281,701 equating to an energy savings of 6.6% over the ASHRAE 90.1. When CO2 based demand control outdoor air is not considered in the ASHRAE 90.1 model, the energy savings achieved for the proposed building model is 20.7% better than ASHRAE 90.1. Given the wide fluctuations in airport terminal building occupancy, a situation which is quite unlike that of most other facilities, we believe that the energy savings resulting from the use of CO2 based demand control outdoor air should be accounted for in the comparison of the \'LEED\' proposed building with a base building which utilizes a minimum outdoor air setting based on peak occupancy. The ruling based on this principle will provide 2 Credits under the \'Energy and Atmosphere Credit 1 - Optimize Energy Performance Category\'.