The Real Life Efficiency of Gas Phase Filters Used in General Ventilation and their Influence on the Indoor Air Quality of an Office Building

Gas phase filters were installed within the air handling unit of a HVAC system feeding 100 % fresh(outdoor) air to an office building. The filter efficiency for ozone (O3) and nitrogen oxides (NO2 and NO) was measured continuously over a one year period as a function of time (filter's life) and outdoor air parameters (temperature and relative humidity). The results show that the filter efficiency varies with time and depends on the temperature and relative humidity of air. It was also shown that the use of this kind of filter improves the indoor air quality as the indoor / outdoor concentration ratio is lower with the use of the gas phase filters than without.