Scientific Efficiency Results

Research Triangle Parks Lab (RTP Labs) performed in fall 2009 tests of filtration efficiency of Andrea.  Air contaminated with formaldehyde was continually passed across the air filter or across the plant and removed from the exit fan of the filter at a constant rate.

In the Andrea test, over a period of three hours, the average inlet concentration of formaldehyde in the air ranged from 28.2 to 31.8 ppm and the average exit concentration of formaldehyde in the air ranged from 12.8 to 15.4 ppm. The average efficiency of air filtration of Andrea based on these tests was 53%. In the plant-only test, over two hours, the average inlet concentration of formaldehyde ranged from 17.2 to 22.1 ppm and the average exit concentration of formaldehyde ranged from 17.1 to 18.8 ppm, giving an average efficiency of air filtration by the plant alone based on these tests of 15%. As further comparison, Chen et al. (2004) measured the formaldehyde efficiency of filtration of a range of HEPA and activated carbon filters and found that the mean efficiency of portable systems was 1.2%.

The very high efficiency of Andrea in comparison to these standard filters reflects both the unique advantage and need for plant filtration in indoor settings and the local cleaning nature of the system.  The Andrea filter, while very efficient at the removal of volatile toxic gases like formaldehyde, cleans air at a relatively slow rate compared with standard HEPA and carbon-filter systems.  It should be used to clean air in local stagnant zones of a home or office where prolonged human presence occurs.

* Chen, Wenhao and Jianshun S. Zhang, Zhibin Zhang, Jim F. Smith. Performance evaluation of air cleaning/purification devices for control of volatile organic compounds in indoor air. Syracuse University Report (2004).