The effect of relative humidity level, VOC type and multiple VOCs on the performance of full-scale GAC filters Ali Khazraei Vizhemehr 1 , Hamid Kholafaei 1 , Fariborz Haghighat 1 *, Chang-Seo Lee 2 1 Concordia University, Montreal, Canada 2 Dectron Inc, Montreal, Canada *Corresponding E-mail: haghi@bcee.concordia.ca SUMMARY This study aims to investigate the effect of three parameters on the performance of full-scale in-duct granular activated carbon (GAC) filters. These factors include the relative humidity level, VOC type and multiple VOCs. The full-scale tests were carried out in a test rig similar to ASHRAE standard 52.2 for a fixed bed filled with GAC. And The GAC was challenged with three different single VOC (i.e. toluene, n-hexane and MEK) and a ternary mixture of aforementioned compounds. This comparison shows how the presence of other compounds in the mixture influences the performance of the filter in removing each VOC. The maximum capacity and breakthrough time are notably reduced when GAC was challenged with the mixture. For single gas challenge test of n-hexane, the effect of relative humidity (i.e., 25%, 40% and 55%) was also investigated. IMPLICATIONS This study involves the analysis of different parameters on the GAC filters used in building application. The results of these experiments will provide a better understanding of the effect of gaseous contaminants and relative humidity level on the efficiency and adsorption capacity as the performance of the filters. KEYWORDS Indoor Air, relative humidity, VOC, mixture gas adsorption, GAC filter INTRODUCTION Many sources of volatile organic compounds exist in indoor air environment which may adversely influence people’s health and comfort. Recent studies on adsorbent filters have shown that granular activated carbon can be effectively used to limit indoor VOC levels (Haghighat et al. 2008, Bastani et al. 2010). The performance of GAC filters is influenced by the physical properties of the gas contaminants it is exposed to. In general, less volatile compounds with a higher molecular weights and boiling points are adsorbed better on the carbon surface than light and very volatile compounds. GAC is hydrophobic and non-polar. Hence, non-polar compounds adsorb better than polar compounds. The competitive adsorption in the mixture gas test significantly changes the filter’s parameters compared to the single gas test. Water vapor plays an important role in the performance of full-scale GAC filters due to competition between water vapor and challenged VOCs. Although activated carbon is hydrophobic and has negligible affinity for water vapor, previous studies have shown that high relative humidity (RH> 50%) can negatively influence the performance of activated carbon. Nelson et al. (1976) assessed the influence of the relative humidity on the performance of activated carbon in removing seven VOCs at 1000 ppm and humidity levels of 20 to 90%. Their results show that the effect of relative humidity was minimal for 20%