Reducing Indoor Air Pollutants Through Biotechnology - Biotechnologies and Biomimetics for Civil Engineering - page 186

Fig. 8.1 Scheme of the experimental chamber apparatus used by Xu et al. ( 2011 ). (A) air pump,
(B)N 2 gas cylinder, (C) needle vale, (D) flowmeter, (E) formaldehyde solution (37 %) vessel,
(F) mixing vessel, (G) buffer vessel, (H) gas sampling port, (I) dynamic chamber, (J) water
injecting port
concentrations. The authors, however, did not assess CO 2 concentrations, thus
leading to ambiguity as regards the true effect of the system as a replacement for
HVAC. Rodgers et al. ( 2012 ) installed an active 'Biowall' into a mock residential
house, to investigate its potential energy saving capacity. This system was inte-
grated into an air-conditioning system drawing outside air only, and yielded an
86 % reduction in total energy expenditure for ventilation, when compared to the
air-conditioning system alone.
The only in situ study to show significant reduction in airborne TVOC levels
using passive botanical air cleaning systems is by Wood et al. ( 2006 ), who found
that three or six standard potted plants could produce a steady state in University
offices where indoor VOC concentrations were maintained below 100 ppbv. Thus
the plants only had a measurable effect when VOC concentrations were [100
ppbv, but were capable of reducing any greater concentrations than this to a
minimum level. These findings are in contrast to both mass balance estimates (e.g.
Guieyesse et al. 2008 ) and some experimental findings (e.g. Chen et al. 2005 ),
leading to Guieyesse et al.'s ( 2008 ) suggestion that the current mathematical
evaluation models are inadequate, and there are sources of variability in the bio-
logical studies which the mathematical models do not capture.
Potted plants therefore clearly have some capacity to ameliorate indoor VOC
levels, although there are significant anomalies between empirical evidence and
theoretical modelling, and research is urgently needed in this area to determine