According to USGBC, the addendum was intended to give project teams more flexibility in testing locations. The 1/25,000 SF testing rate is still a good rule of thumb and is acceptable. USGBC is trusting that the project's industrial hygienist will have the best understanding of how to accurately test the spaces in the project. Select spaces to be tested so that each occupiable space type is adequately represented. Additional guidance can be found in the pilot prerequisite for performance-based IAQ.