The BUILDAIR Symposium, the leading conference on the topic of airtightness, is celebrating its 20th anniversary this year. Some may remember its first steps in 1993. Back then, it became clear that there was a great need for a regular exchange of experience among the first 50 providers of measuring servicesin Germany. The new measuring procedure, the “BlowerDoor Test”, completely revolutionized building quality and provided many aspects for discussion for an annual meeting of practitioners in the field. This is how the first BlowerDoor Symposium at the Energie- und Umweltzentrum [Center for Energy and the Environment] am Deister came about.