I have been certifying many large office buildings in NYC and would like some help on the below:

I provide a survey to building occupants in multiple forms (e.g. online survey, in-person, emailed attachment), how can i ensure that no double-counting of occupants has occurred?

In previous buildings we would ask for some unique identifier (e.g. first initial and last name, ID card #, etc.). However, we encountered many people that understandably did not want to provide this information, even though we informed them that the purpose was only to remove duplicate entries from the results. I would like to remove these unique identifier questions from the survey to increase the response rate, and have been racking my brain on how to do this.

My best alternative is: at the top of the survey place a check box next to the following statement: "This is the first and only time that I have filled out this survey and I confirm that I am a regular building occupant."

Does anyone think this route would work in the eyes of the GBCI reviewers? Does anyone have any alternate suggestions?