The problems of air change and airtightness in buildings are not sufficiently recognized in Poland, which results in the lack of precisely defined standards for building design. This paper discusses the correlation between airtightness and air change rates and presents measured and calculated air change rates with and without different sources of airflows in occupied houses. It discusses also the influence of pressure differences that were measured on the air change. The results of tests can be used to verify present standards in the field of airtightness and air change rates and give the basis for further testing of these processes.