Objective: To test whether a reduction in air temperature within the clinical range [37 C to 30, 100% relative humidity (RH)] altered mucus transport velocity (MTV) and ciliary beat frequency (CBF) in an in vitro ovine tracheal model. Design: Controlled laboratory study. Setting: University research laboratory. Subjects: Farm-reared sheep. Interventions: Tracheae were mounted flat in an organ bath. Krebs Henseleit bathed the serosal surface and air at 100% (RH) was passed over the mucosal surface at 4 l/min.