Air Quality and Thermal Comfort in an Office with Underfloor, Mixing and Displacement Ventilation

An underfloor ventilation system providing three different airflow patterns, a mixing ventilation system, and a displacement ventilation system utilizing a wall-based diffuser were tested in a mock-up of a typical office. The systems were operated under identical conditions. The criteria for evaluation included the distribution of air exhaled by two breathing thermal manikins, pollution emitted from the floor covering, velocity and temperature. It was shown that the inhaled air quality in rooms with underfloor ventilation depends on the association between the vertical penetration height of supply airflows and the stratification height of exhaled pollutants. However, no difference between the ventilation systems was found in regard to the floor pollution. The main conclusion is that underfloor ventilation systems providing a short vertical throw can ensure both a high air quality and a lower risk of thermal discomfort as compared to displacement ventilation and underfloor ventilation with a horizontal discharge pattern.