We are utilizing LEED for a 5-story, 50 unit multifamily apartment building in downtown Seattle. As with other residential buildings utilizing the commercial rating system, we will meet the intent of Prerequisite 2 by prohibiting smoking in all common areas and by placing all residential units at negative pressure, with the corridors at positive pressure. All of the units are designed and constructed with continuous exhaust ventilation. Both our consulting engineer and our technical consultant from the Energy Management Services division at Seattle City Light have recommended utilizing a manometer to test for the pressure differential and verify negative pressure in the units. A digital manometer would be used to test the pressure differential between the in unit private residential spaces and the common area corridors and common spaces in the building when all systems are fully operational. Two units will be tested per floor [a total of 10 units and a sampling rate of 20%] to establish the negative pressurization and atmospheric isolation of the units from the common spaces. A blower door test of the units will also be done to establish specific areas of potential air leakage and the overall air tightness of the residential units. Would you please verify that the above testing method will allow us to meet the requirements of EQ Prerequisite 2. Previous credit interpretation requests (1/18/2002 & 1/31/2003) have been based on the use of a tracer gas testing to verify negative pressure. Should this method be required in lieu of the manometer testing suggested above, would you please elaborate on your response of 1/18/2002 in which you note that the tracer gas testing study needs to be "properly designed"? Does this simply mean, as you suggest, testing an appropriate variation of unit locations (as we would do in conducting the manometer testing) or is there a more detailed protocol that must be followed?