Describes a study carried out in order to examine the relationships between the ventilation rate and the type of ventilation system on one hand, and objective nasal measures on the other. The method was to carry out a standardised investigation which included acoustic rhinometry and nasal lavage at a school. 279 persons at 12 primary schools in Sweden were invited and 84% participated. Both crude bivariate analysis and multiple regression models were used to analyse the relationships between nasal symptoms, nasal patency and the concentration of biomarkers and the type of ventilation system, the air exchange rate and the temperature. Concludes that a lower degree of nasal patency and increased levels of ECP and lysozyme in nasal lavage were associated with a lower air exchange rate. Although mechanically ventilated schools had higher air exchange rates, they were associated with more nasal symptoms. Concludes that both a low air exchange rate and mechanical ventilation systems based on dilution can be associated with reduced nasal patency. The best performing school had a displacement system.