Gas phase air filters in HVAC systems for better indoor air quality

Activated carbon filters have been installed within the air handling unit of an HVAC system feeding 100% fresh air to an office building. The filters efficiency against ozone (O3) and nitrogen oxides (NO2 and NO) as function of time and outdoor air parameters (temperature, relative humidity) has been measured continuously over a one-year period. The results show that the filters efficiency is high (generally between 70 to 90 %) and varies along time with temperature and relative humidity of air. It has also been shown that the use of this kind of filters improves the indoor air quality as the indoor gas concentrations (O3 and NO2) inside the building are lower after the filters have been installed. This paper reports on the first 6 months of the study( May to November 2005)