The various Excel files included in this dataset report data from tests performed to assess the technical capabilities of the Ground CO2 Mapper, a newly developed tool that can be used to help reduce uncertainty in the mapping of geological or anthropogenic CO2 leakage from the ground surface. These files include data from a number of laboratory experiments as well as tests performed at a controlled release site and a natural site where geological CO2 is released over a large area. This dataset was used to create the various figures presented in the article "Development and testing of a rapid, sensitive, high-resolution tool to improve mapping of CO2 leakage at the ground surface" by Graziani, Beaubien, Ciotoli and Bigi to be published in Applied Geochemistry.