Performance evaluation and demonstration of an activated carbon-based botanical air filtration system

A botanical air filtration system based on the principle of physical adsorption by activated carbon and VOC consumption by microbes in the plant's root system was developed. The filtration system was integrated in the HVAC system for a new office space (96.8m²). The room pollutant concentrations (hexanal, α-pinene, pentanal, toluene, formaldehyde and acetaldehyde) were monitored by Proton Transfer Reaction Mass Spectrometry (PTR-MS) under several combinations of outdoor airflow rate and air filtration flow rate: 5% outdoor air (119m³/h) in total air supply to the space plus botanical filtration system periodically on and off; 10% outdoor air without air filtration; 25% outdoor air without air filtration; and 50% outdoor air without air filtration. The results show that 5% outdoor air plus botanical filtration leads to the similar indoor formaldehyde/toluene concentration level as 25% outdoor air without filtration, which means the filtration system is equivalent to 20% outdoor air ventilation (476m³/h). The result was within 10% of the clean air delivery rate (527m³/h) obtained in a full-scale chamber test. The filtration system was then operated continuously for 60 days to investigate the long-term performance. Results indicate that the botanical filter performed consistently well on the formaldehyde and toluene removal over the relatively long testing period of 60 days while running continuously.