We contacted individuals, groups or organisations that were known to have collected representative spirometry data from asymptomatic lifelong non-smokers, using methods and techniques that complied with temporal international recommendations. Most invitations arose from searches of the literature for titles in peer reviewed journals. All data were anonymised prior to submission, and accompanied by information detailed in a data collection template. Any person, group or organisation sharing data with the working group specified in writing that their ethics committees or organisations had given permission for the data to be used in a research publication.