I found a thread from 2011 discussing the Addendas released 5/9/11 removing the footnote that was previously changed under Addenda reliease 9/19/10. Can someone set me straight if i'm not interpreting the 5/9/11 addenda correctly? I interpret the new requirement as: Case 1) If I have a system that serves only 1 space that is densely occupied, the only requriement of this credit is a CO2 sensor. An OA measurement device is not required. Case 2) System that serves 20% or more non-densely occupied spaces, and has one densely occupied conference room. I will need to provide a CO2 sensor for the Conference room AND an OA measurement device on the system, since i'm serving 20% or more densely occupied spaces. Thanks!