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Investigation of A Potted Plant (Hedera helix) with Photo-Regulation to Remove Volatile Formaldehyde for Improving Indoor Air Quality


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Formaldehyde is the most common volatile organic compound (VOC) emitted from household materials and is associated with many health risks, including sick building syndrome. A potted Hedera helix was used as an air purifier to remove the gaseous formaldehyde. Development of a test platform is necessary to evaluate the indoor performance of air cleaning protocols. The box modulation with a novel volatile pollutant-emitting source was applied in an air quality monitoring experiment to mimic a non-ventilated workplace. The environmental conditions and the pollutant concentrations in the air were measured in real time, and the monitoring data was uploaded to cloud storage media by a wireless technique. Compared with natural dissipation, our results demonstrate a 70% decrease in the required time to achieve 1.0 ppm of gaseous formaldehyde using the biological purifier. In addition, the effect of photo-regulation was not significant in the use of potted plants to remove gaseous formaldehyde. Our study provides an accurate and available platform for the public to determine the health risks of VOCs in their buildings.
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Aerosol and Air Quality Research, 17: 2543–2554, 2017
Copyright © Taiwan Association for Aerosol Research
ISSN: 1680-8584 print / 2071-1409 online
doi: 10.4209/aaqr.2017.04.0145
Investigation of A Potted Plant (Hedera helix) with Photo-Regulation to Remove
Volatile Formaldehyde for Improving Indoor Air Quality
Ming-Wei Lin
, Liang-Yü Chen
, Yew-Khoy Chuah
1 Department of Energy and Refrigerating Air-Conditioning Engineering, National Taipei University of Technology, Taipei
10608, Taiwan
2 Department of Biotechnology, Ming-Chuan University, Taoyuan 33348, Taiwan
Formaldehyde is the most common volatile organic compound (VOC) emitted from household materials and is
associated with many health risks, including sick building syndrome. A potted Hedera helix was used as an air purifier to
remove the gaseous formaldehyde. Development of a test platform is necessary to evaluate the indoor performance of air
cleaning protocols. The box modulation with a novel volatile pollutant-emitting source was applied in an air quality
monitoring experiment to mimic a non-ventilated workplace. The environmental conditions and the pollutant concentrations
in the air were measured in real time, and the monitoring data was uploaded to cloud storage media by a wireless
technique. Compared with natural dissipation, our results demonstrate a 70% decrease in the required time to achieve 1.0
ppm of gaseous formaldehyde using the biological purifier. In addition, the effect of photo-regulation was not significant
in the use of potted plants to remove gaseous formaldehyde. Our study provides an accurate and available platform for the
public to determine the health risks of VOCs in their buildings.
Keywords: Phyto-degradation; Ornamental plant; Gas sensor; Air cleaning; Photoreaction.
Air quality is a global problem causing economic loss
and human health threats (Seppänen and Fisk, 2006). Serious
health problems are related to sick building syndrome, which
is usually associated with the quality of indoor air (Mullen
et al., 2016; Mandin et al., 2017). In urban areas, most
citizens have long-term exposure to large amounts of harmful
chemicals indoors, whether it’s at home or working at the
office (Zheng et al., 2011; Shi et al., 2015; Lukcso et al.,
2016). People are usually exposed to a higher intake or
breathe in a greater concentration of air pollutants because
these pollutants are more prevalent in indoor than outdoor
environments (Zhang et al., 2017).
However, increased industrial development and urban
activities have brought about worsened outdoor air quality
(Alam et al., 2016). Air pollution in China and India has
received a lot of scientific attention, even affecting the lives of
people in neighboring countries in Asia (Venkatachalam,
2017). People spend more time indoors, while outdoor air
* Corresponding author.
Tel.: +886-3-3507001 ext. 3773; Fax: +886-3-3593878
E-mail address: (L.Y. Chen); (Y.K. Chuah)
pollution has caused serious hazards to health (Zhang et
al., 2017). Understanding and controlling indoor air
quality can help reduce the risk of indoor health concerns,
especially Legionnaires' disease (Sundell, 2017), respiratory
allergy (Guan et al., 2016; Lukcso et al., 2016) and children’s
asthma (Huang et al., 2016).
As shown in Fig. 1, indoor air quality is dominated by
many dynamic processes, including air exchange, human
activities, and pollutants transferring within the building,
weather, and building occupants (Zheng et al., 2011). People
usually notice uncomfortable symptoms or illness after
working for several hours, and feel better after leaving the
building for some days. The amount of time they spend in
the building is associated with the health effects (Francisco
et al., 2017). However, specific pathogens or causes cannot
be identified in most cases. Therefore, a well-defined
experimental platform needs to characterize the major
components, distributions, boundaries, exchangeable rate,
and loading between the system and surroundings (Freijer
and Bloemen, 2000; Yang and Zhang, 2008; Demou et al.,
2009; Kim et al., 2010). The indoor air quality is significantly
influenced by infiltration into the building mainly through
the ventilation system and to a lesser extent, through
windows or cracks (Saraga et al., 2017).
Common indoor air pollutants can be categorized as
volatile organic compounds (VOCs), microbial contaminants,
gaseous contaminants, and particulate matter (PM). The air
Lin et al., Aerosol and Air Quality Research, 17: 2543–2554, 2017
pollutants related to the sources of air pollution are listed
in Table 1. Thus, the pollution sources must be first identified
for the removal of indoor air pollutants. Formaldehyde
(HCHO) is one of the most common VOCs affecting indoor
air quality and the health of occupants in buildings (Brown
et al., 2015). Recent observation also demonstrated that the
HCHO is the most serious air pollutant in the decorated
residences and public places (Chang et al., 2017). Carbon
dioxide (CO2) levels can be used as an indicator of biotic
odors, and a health risk should be considered at very high
levels, greater than 5000 ppm (Rackes and Waring, 2013).
The chemical contaminants exist in the indoor environment
within the different dynamic behaviors and frequencies.
Ventilation is an effective way of ameliorating air quality
that works by diluting the concentrations of indoor pollutants,
but it increases energy use because the utilization of indoor
air handling systems must increase (Ciuzas et al., 2016;
Francisco et al., 2017). Besides, using effective means to
reduce indoor air pollution and improve air quality are
important issues for building occupants and users in non-
ventilated places, like hospitals and laboratories (Brown et
al., 2015; Lucas et al., 2016; Verriele et al., 2016; Bradman et
al., 2017). Indoor air handling systems with HEPA filters
control the ambient environmental conditions, including
the temperature, humidity, air flow and air cleaning (Russell
et al., 2014). However, filtration does not reduce the levels
of all indoor air pollutants, and some types can actually
exacerbate the problem (Yu et al., 2006). Chemicals or
particles can penetrate indoors through the building envelope,
affecting the indoor PM2.5 levels in real housing units with
a controlled indoor-outdoor pressure differences (Choi and
Kang, 2017). Therefore, a well-defined performance metrics
of air cleaner is need to developed for the indoor air quality
management (Hodgson et al., 2007; Yan et al., 2008).
The use of plants to improve indoor air quality was
investigated by the U.S. National Aeronautics and Space
Administration (NASA) to explore the possibilities of long-
term space habitation for closed environments in space
missions (Wolverton et al., 1989). The pioneering screening
studies by Wolverton and colleagues showed over 50 species
Fig. 1. Schematic assessment framework of indoor air quality, including a series of dynamic life cycles of chemicals,
biological activities, as well as the physical factors and exchange with the outdoor air (surroundings).
Tab l e 1 . Sources and types of pollutants in the indoor air.
Source Major Pollutions
Outdoor air exchange PM, Ozone, Nitrogen oxides, Dust, Pollen, Carbon oxides
Building materials, paint, glues, upholstery, wallpapers Benzene, Toluene, Insects, Formaldehyde, Alcohols
Furniture and decorative supplies, televisions,
refrigerators, carpets, heater
Formaldehyde, PM, Fungi, Insects, Benzene, Ethyl acetate,
Carbon oxides, Ammonia, Acetone, Fungi
Office equipment, printer, paper, photocopiers, inks,
computers, fax, cosmetics
PM, Ethanol, Formaldehyde, Carbon oxides, Ozone,
Nitrogen oxides, Ammonia, Acetone, Ester, Bio-aerosol
Activities of households, cooking, cleaning, smoking,
Carbon dioxide, PM, Benzene, Ether, Acetate, Fungi,
Alcohols, Eater, Bio-aerosol
Pets and planting PM, Ammonia, Sulphur compounds, Carbon dioxide,
Methane, Ethyl acetate, Insects, Bio-aerosol
Lin et al., Aerosol and Air Quality Research, 17: 2543–2554, 2017
of houseplants had air-cleaning capacity and reduced
VOCs levels in the air (Wolverton et al., 1989; Wolverton,
1996). English ivy (Hedera helix) is an evergreen climbing
plant that is well adapted to indoor conditions. Hedera helix
climbs by means of aerial rootlets with matted pads which
cling strongly to the substrate. The leaves are of two types,
with five-lobed juvenile leaves on creeping and climbing
stems, and unrobed adult leaves on fertile flowering stems
exposed to sun. Different varieties of Hedera helix are
widely cultivated as ornamental plants, preferring moist,
shady locations and avoiding direct exposure to sunlight.
Hedera helix is also usually listed as a top 10 houseplant
air cleaner for VOCs removal (Yang et al., 2009).
Thus, the potted Hedera helix and HCHO were used as
model plants and air pollutants to appraise the green
technique of improving indoor air quality in this study. Two
sources of air pollution in different emitting modes were
first utilized in a well-defined test box. The impacts of
biological factors on environmental conditions were also
evaluated by observations with quantitative data in real
time. A wireless air quality monitoring system was conducted
with field studies to verify the feasibility of prediction
models and estimate the exchange between the system and
its surroundings (Kang et al., 2016). The multiple boxes-
modeling was used in a laboratory-type test to describe the
performance of planting on the cleaning of indoor air.
Although the earlier laboratory studies have demonstrated
the ability of bioremediation technologies to remove VOCs
(Kim et al., 2008; Xu et al., 2010; Xu et al., 2011; Dela
Cruz et al., 2014; Gawronska and Bakera, 2015; Pandey et
al., 2016; Hong et al., 2017), no experimental field-study
has been made to investigate the potted-plant can bring
about significant reductions of VOC pollution in the real
environments. Our study might provide an accurate and
relatively accessible platform for the public, interior designers
and engineers to determine if the health risks of VOCs in
their building space. The phyto-remediation not only is
able to remove the VOCs from air but also stabilize the
temperature and humidity, to improve people's mental health.
Plants Materials
Four potted plants (Hedera helix) were purchased from
the Jian-Kuo flower market in Taipei, Taiwan. All plants
were chosen to be free of insects and pathogens and cultured
in 8-cm-diameter pots with sterilized media. Before use in
experiments, clean water would be poured into the pot,
which was covered by aluminum foil to avoid withered
planting and infiltration of gaseous pollutants.
Setup of Experimental Box for Air Quality Monitoring
As shown in Fig. 2(A), the experimental platform of air
quality monitoring was designed as a controlled box to
mimic the indoor space and operations in this study. A
quasi-closed box was made of acrylic polymer in 90(L) ×
50(W) × 50(H) cm and equipped with two recirculating
fans; one illumination unit; and two exchangeable ports. The
recirculating fans were used to promote the composition
uniform of air quality in the experimental box. Two
fluorescent tubes (T5/2FT 14W, daylight, Wellypower
Optronics Corporation, Taiwan) were used to meet a
specification of 16(D) × 549(L) mm, with 1200 lm and
color temperature of 6500K, and were placed on the upper
layer of the box to meet the illumination requirement. The
spectrum of the fluorescent tube was measured by a
UV/visible/infrared micro-spectrometer (GREEN-Wave
UVNb-25, StellarNet Inc., USA) and characterized as shown
in Fig. 2(B). The irradiation intensity was also validated
using a multi-sense optical radiometer (MS-100, Ultra-Violet
Products Ltd., UK).
The monitoring instruments were installed for air quality
and environmental conditions in real time. An illuminometer
(TENMARS YF-1065, TECPEL Co., Taipei, Taiwan) and
combo air quality sensors (AQM-100 and APM-200, AIGO
TECH Co., Taipei, Taiwan) were used in the study. Each of
the major sensors used in this work was characterized and
listed in Table 2.
Exposure to Gaseous HCHO with Different Emission
Two types of emission source of gaseous HCHO were
used to examine the removal efficiency of HCHO pollution
in indoor environments. One was the spraying of 2 ml of
14% HCHO liquid into the experimental box and using an
atomizing nozzle to make the molecules vaporize and
rapidly disperse. The emission mode of the volatile pollutant
was termed the “fast discharge”. The other emission mode
was termed “slow release”, whereby 1 ml of 14% HCHO
liquid was poured in a glass dish with a porous material. In
the slow release mode, the HCHO molecules were vaporized
and diffused into the box space.
The 14% HCHO liquid was purchased from First-
Chemical Works (Taipei, Taiwan). Ultrapure water produced
by a Milli-Q system (Millipore, USA) was used as a solvent.
Experimental Design and Observation
Several preliminary studies were carried out for
observation requirements, such as the maximum detectable
level, the background level, and the time required for natural
decay under the experimental conditions. The air quality of
the experimental box was conditioned to the background
standards before every treatment. For the target pollutant,
the HCHO concentration should be less than the 0.1 ppm
of DNEL in the air (Johansson et al., 2016). Therefore, the
active ventilation would make the HCHO level decrease to
0.03 ppm for 1 hour.
Every six hours, the illumination system was toggled
automatically between light and dark environments. The
observations without a planting were considered a control
for the system under an indicated emission mode of air
pollutant. The eight parameters listed in Table 2 were
measured and collected in real time. Once the HCHO level
in the air was attenuated to 0.05 ppm as the low removal
efficacy, the observations were ended. The time series of
experimental data per minute were recorded on a computer
and uploaded to a cloud storage media by Wi-Fi router.
Lin et al., Aerosol and Air Quality Research, 17: 2543–2554, 2017
Fig. 2. Illustration of an experimental system for air quality monitoring. (A) The modeling box was used with a potted
Hedera helix, an illumination unit and the data acquired network in this study. (B) The emission spectrum of fluorescent
lamps used in this study was measured at a wavelength range of 190–1050 nm.
Tab l e 2 . Sensors and their specifications.
Parameters Measurement Response Range Sensitivity Symbol (Unit)
1. Illumination Si Photodiode
0.120000 ± 0.1 Luminance (Lux)
2. Temperature e-Resistivity
30100 ± 0.1 Temp. (°C)
3. Relative Humidity e-Conductivity 090 ± 3% RH% (%)
4. Formaldehyde Electrochemistry
05.000 ± 0.001 [HCHO]air (ppm)
5. Carbon Dioxide NDIR 05000 ± 5% [CO2]air (ppm)
6. Carbon Oxide n
0100 ± 5% [CO]air (ppm)
7. Total Volatile Organic Chemicals n
Semiconductor 0.1250.6 ± 5% TVOC (ppm)
8. Ultrafine Particles n
0999 ± 10% PM2.5 (ppb)
The superscript of “nd” is indicated the non-detectable data monitored by the sensor, which was used in this study.
Statistical Analysis
All data represent the mean with a standard deviation of
independent experiments. Only the control experiment of
slow release mode was executed once, because the
observation was time-consuming. The results were analyzed
using the unpaired, two-tailed Student’s t-test.
Characterization of Indoor Air Quality Changes
The air quality of the experimental box to mimic indoors
is a constantly changing interaction of complex factors
affecting the types, levels and importance of pollutants in a
Lin et al., Aerosol and Air Quality Research, 17: 2543–2554, 2017
controlled environment. Indoor temperature, relative
humidity, and illumination are the environmental factors
affected and controlled by the ambient surroundings and
the observer’s activities. As shown in Fig. 3, only five
environmental and air quality parameters were available
and detectable for this observation on March 4, 2017. In
addition, illumination was an operating factor for photo-
regulation. Luminance, carbon dioxide, temperature and
relative humidity were immediately affected by opening
the box with the air exchange at Event (1). The box air was
rapidly cooled and humidified while the spraying of HCHO
liquid atomized the water molecules and absorbed heat
Fig. 3. Example of the time courses of environmental and air quality parameters in the box by the monitoring data in
March 4, 2017. The blue-lined area represents a period of data loss. The numbered events indicate the effects of the
processes, the box opening and plant setting were carried at Event (1); the 2 ml HCHO liquid was injected into box at
Event (2); the illumination unit was turned off at Event (3); the illumination unit was restarted at Event (4).
Lin et al., Aerosol and Air Quality Research, 17: 2543–2554, 2017
from the air at Event (2). The raised level of carbon dioxide
was caused by the breathing of the observer. With the
molecular diffusion and heat exchange between the system
and surroundings, these parameters gradually returned to a
stable range. The alterations in illumination at Event (3)
and Event (4) made subtle changes in the relative humidity
and carbon dioxide.
The harmful gaseous pollutants, such as carbon monoxide,
total volatile organic chemicals and fine particles were non-
detectable and less than the toxic levels in these observations.
A good indoor environment establishes the range of
environmental conditions acceptable to achieve healthy
and thermal comfort for human occupancy (Xiong et al.,
2015; Sundell, 2017). For thermal comfort purposes, the
air temperature and the relative humidity should be held in
the range of 22–26°C and 40–60%, respectively. After
spraying pollutants into the box, the gaseous HCHO level
in the air was raised over the upper limit level of sensor
measurement (5 ppm) and was then reduced with time.
In this observation, the removal of gaseous HCHO presents
an exponential decay curve with complicated regulations and
multiple mechanisms via illumination and plants. Note, a
slightly increased signal was present in the attenuated curve
after the occurrence of Event (3) while the illumination
was turned to dark. The phenomenon reveals an emitting
source contributes gaseous pollutants into the box air more
than the removal amount from the box air. We believe the
plants play an important role in the removal of gaseous
HCHO and were regulated by illumination.
Effects of Pollutant Emitting Modes on Indoor Air
HCHO occurs naturally and is an important industrial
chemical. Workplaces in health care facilities, research
institutes, and mortuaries may present the high exposure
risks due to the use of chemicals (Demou et al., 2009).
However, many studies have investigated the removal
kinetics of VOCs with a short-term exposure in a controlled
space. Studies based on long-term exposure are rare in the
literature review (Hun et al., 2010; Nielsen et al., 2017).
Thus, we presume different types of emission sources of
VOCs and their degradation patterns in Fig. 4(A) from the
life experiences. A combination of slow discharge and
cyclical release modes mimicked the long-term emission
source of indoor VOCs in this study. The performance of
the emission sources should be validated and characterized
for different experimental requirements. The emission source
in the fast discharge mode was applied in this short-term
study (less than ten hours), and one of the slow release
modes was used for the long-term study, such as the
botanic filter application and health risk assessment. Urea-
formaldehyde (UF) is a non-transparent thermosetting
resin or plastic used in adhesives, finishes, particle board,
and molded objects (Broder et al., 1991). These UF resins
are a class of thermosetting resins of which resins make up
80% produced globally for improving tear strength, in
molding electrical devices. Thus, the emission source with
porous material could mimetic the dynamics of indoor
VOCs production (Hun et al., 2010).
In Fig. 4(B), the gaseous HCHO level in the air was
rapidly reduced to a safe level in the fast discharge mode;
but the other observation needed more time to achieve a
similar level in the slow release mode. Our previous study
demonstrated the temperature and relative humidity of
indoor air are not sensitive to HCHO removal via natural
dissipation and photo-degradation (Lin et al., 2017).
However, the time course of gaseous HCHO removal
presented a photo-regulated phenomenon by switching the
illumination environment. The lighting would increase the
air temperature and indirectly enhance the vaporized rate
of HCHO from the supported material into the air. Real
absorbents have pores of various sizes; the diffusion plays
an increasingly important role to decrease the observed
activation energy, and the reaction order approaches unity
(Lin et al., 2017).
Otherwise, the positive effect of illumination would also
contribute to the removal of gaseous HCHO through
photo-degradation. Due to the exponential decay curve of
gaseous HCHO removal, the apparent kinetic equation was
proposed as follows: [HCHO]air (t) = [HCHO]air (0)·e–K+(t–0),
and the removal rate of gaseous HCHO was derived from the
logarithmic plot in Fig. 4(C). The slope of the logarithmic
curve with time presents an apparent rate constant, K+.
With Arrhenius temperature dependencies for the reaction
and diffusion, the observed activation energy would be
approximately one-half the true activation energy by
strong pore resistance, Eobs E
true/2. The results of the
kinetic observations clearly demonstrate an approximated
one-stage matter in the slow release pollution and a two-
stage mechanism depended on the concentration for the
fast discharge pollution.
Performance Evaluation of Plants on Volatile HCHO
Current performance assessment of the air cleaning
primarily has been occurred in laboratories, often using
high challenge concentrations of chemicals, low airflow rates,
and single contaminant species in a controlled environment
(Yu et al., 2015). In generation, a performance of air
cleaning was determined by two ways including a direct
upstream versus downstream measurement and empirical
determination with a single zone mass balance model
(Thunyasirinon et al., 2015; Ciuzas et al., 2016). The air
purification performance could be assessed by the removal
amount, the removal rate, and the required time to achieve
the acceptable values of air quality. For short-term
assessments, the removal of contaminants is the most used
indicator in quantitation.
However, the World Health Organization (WHO)
established an exposure limit of gaseous HCHO of 0.08 ppm
for 30-minute periods (Salthammer et al., 2010; Nielsen et
al., 2017). The main human exposure pathways of HCHO
are inhalation of gaseous HCHO from the air or
transdermal absorption of aqueous HCHO (Gelbke et al.,
2014). Therefore, the required time is more available as the
indicator to evaluate the performance of a biological method
for indoor HCHO removal (Darlington et al., 1998; Xu et
al., 2011; Dela Cruz et al., 2014).
Lin et al., Aerosol and Air Quality Research, 17: 2543–2554, 2017
Fig. 4. The effect of emitting sources with different modes on gaseous pollutants removal without plants. (A) Patterns of
gaseous pollutant concentration are proposed with the three types of emission sources. (B) The time courses of HCHO
concentration were recorded with the fast discharge mode and the slow release mode. (C) Plotting of the logarithmic
concentration of gaseous HCHO versus the time was used to characterize the removal rate of HCHO. The grey block
means the experiments were performed without illumination (in dark).
For comparison, the control experiments were performed
in the box system without household plants. As shown in
Fig. 5(A), treatment with potted Hedera helix could slightly
accelerate the removal of gaseous HCHO from the air
under the fast discharge mode of the emission source. The
efficiency of potted Hedera helix was greater at lower levels
of gaseous HCHO, at less than 1 ppm. This result shows
the botanic filters are not suitable to treat acute exposure to
VOCs. However, the efficiencies of potted Hedera helix
were significantly improved for gaseous HCHO removal
under the slow release mode of the emission source, as
shown in Fig. 5(B). The required times to achieve 1.0 ppm
HCHO were 58.5 hours and 17.1 hours using natural
dissipation and the biological purifier, respectively. The
Lin et al., Aerosol and Air Quality Research, 17: 2543–2554, 2017
Fig. 5. The time efficacies of gaseous HCHO removal with a potted Hedera helix. Evaluation was based on the time
required to achieve the indicated concentration (1.0 or 0.5 ppm) of gaseous HCHO under the emission source of (A) fast
discharge mode, or (B) slow release mode. For comparison, the control experiments were performed in a box system
without household plants. The difference was designated as the level of significance with * (P < 0.5), with ** (P < 0.05) or
with *** (P < 0.01).
required times to achieve 0.5 ppm HCHO were 67.6 hours
and 20.9 hours using natural dissipation and the biological
purifier, respectively.
People are exposed to localized and accumulated doses
of VOCs due to staying indoors for a long time (Wolkoff et
al., 1998). Usually, the most effective way to improve indoor
air quality is to eliminate individual sources of pollution or
reduce their emissions. However, most emission sources of
indoor VOCs are continuous and slow release (Manoukian
et al., 2016). Gaseous HCHO can be removed by many
pathways, including diffusion, adsorption, polymerization,
photolysis and photocatalytic oxidation decomposition (Li et
al., 2014). Our results demonstrate plants have an advantage
in treating chronic pollution and the residual pollutants in
ambient air.
Photo-Regulated Effects of Hedera Helix on Gaseous
HCHO Removal
Under proper light irradiation, the photosynthesis of
green plants utilizes the carbon dioxide in air to provide
carbohydrates and energy source for growth. The volatile
chemicals are absorbed and metabolized by the physiological
pathways of the plants, and the efficiency of pollutant
removal depends on the plant species, time, light intensity
and pollutant species (Kim et al., 2008; Wang et al., 2014).
The data set of long-term monitoring was chosen to
investigate the photo-regulated effect on improving indoor
air quality with plants. Thus, the emission source of gaseous
HCHO was used as the slow release mode to provide a
detectable level in the air. In Fig. 6(A), the gaseous HCHO
level was decreased and the removal rate tended to slow
after exposure of 8 hours. For high level region, the time
course of gaseous HCHO is changed significantly in the
removal rate. In addition, the system illumination was
periodic switched every six hours. The time-lag effects
were also observed in these irradiation events. The Fig. 6(B)
shows illumination could assist the Hedera helix in removing
gaseous HCHO at lower levels, at less than 1 ppm. Thus,
gaseous HCHO removal by Hedera helix was again validated
as a concentration dependent matter.
The carbon dioxide levels in the box air could be an
indicator of respiration and were shown in Fig. 6(C).
Lower levels of carbon dioxide were observed in the light
environment, compared with the dark environment. The
Lin et al., Aerosol and Air Quality Research, 17: 2543–2554, 2017
Fig. 6. Effects of illumination on HCHO removal, kinetic rate and carbon dioxide level in air. (A) The time courses of
HCHO concentration were recorded in the slow release mode from March 12 to 15. (B) The kinetic rate of gaseous HCHO
removal was evaluated for less harmful concentrations of HCHO on March 13. Plotting of the logarithmic scale versus the
time was used to display the removal rate with Hedera helix. (C) The time courses of carbon dioxide concentration were
recorded and compared to the HCHO removal at March 13. The grey block means the experiment was carried without
illumination. The symbols of D L and L D show the experimental environments changed from dark to light and from
light to dark, respectively.
effectiveness of photosynthesis was inhibited by the high
level of carbon dioxide in the air. The post-illumination
CO2 burst was observed after the illumination turned off
(LD). For C3 plants, light respiration will counteract
about 30% of the photosynthesis. Oxygen is consumed during
the process and generates carbon dioxide. Therefore, reducing
light respiration is considered one way to improve the
effectiveness of photosynthesis.
Biological regulation is a complex, adaptive and dynamic
process, and the illumination and planting has a strong
Lin et al., Aerosol and Air Quality Research, 17: 2543–2554, 2017
impact on the ecological stability of human life. Some
studies reported the biogenic VOC has an indirect impact
on the lifetime of greenhouse gases and the secondary
organic aerosol formation in the atmosphere (de Oliveira
and Moraes, 2017). However, the benefit outweighs of
planting for improving the indoor air quality is larger than
the hazard risk from biogenic toxins.
Air cleaning techniques with low-energy consumption and
green properties are modern trends (Lu et al., 2010). To
gauge the potential benefits of these devices and techniques,
metric tools based on indoor air quality modeling and
performance data from field testing must first be applied
(Ozturk, 2015). A well-defined experimental platform with
an emission source of volatile organic chemicals was
investigated to evaluate the performance of a potted plant
in removing gaseous HCHO. The slow-release mode of
emitted pollution was first utilized to fulfill the requirement of
mimicking an indoor environment in a long-term monitoring
experiment. The contributions of natural dissipation,
photo-degradation and the botanic filter were assessed
quantitatively. Volatile HCHO levels can be reduced using
potted plants, which provide additional ornamental features.
The experimental results show that potted Hedera helix
can reduce 70% of the required time to reach 0.5 ppm of
gaseous HCHO when compared with natural dissipation.
Potted Hedera helix can also remove residual HCHO from
the environment, thus improving indoor air quality.
The authors thank the assistances from the Lecturer Lin,
Liang-Tse in the Department of Civil and Construction
Engineering at National Taiwan University of Science and
Technology in the works of electronics and data acquirement.
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Received for review, April 21, 2017
Revised, June 16, 2017
Accepted, August 25, 2017
... Most phytoremediation studies have been conducted on the removal of VOCs, especially formaldehyde and benzene due to their very hazardous properties and adverse health effects (Lin et al. 2017;Parseh et al. 2018;Teiri et al. 2018a;Torpy et al. 2018). However, different plant species have different behaviors in removing the contaminants. ...
... The particle concentration in apartments where residents have high levels of physical activity and use devices such as fixed bicycles daily or in places where they use printers or copy devices are much higher than in other places (Gawrońska and Bakera 2015;Irga et al. 2017). Contaminants such as formaldehyde, benzene, toluene, and many other VOCs are penetrated to the plant through the stoma and removed (Mosaddegh et al. 2014;Kim et al. 2016;Lin et al. 2017;Teiri et al. 2018a). Since plants are also able to remove contaminants from the air in the dark place and when the stoma is closed, this indicates that many contaminants are absorbed by the cuticle (Salthammer et al. 2010;Xu et al. 2011;Teiri et al. 2018a). ...
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In recent decades, indoor air pollution has become a major concern due to its adverse health effects on the inhabitants. The presence of fine particles (PM2.5) and hazardous volatile organic compounds (VOCs), such as formaldehyde and benzene, in indoor air and their proven carcinogenic effects, has raised the attention of health authorities. Their very difficult and expensive removal by chemical and mechanical methods has led researchers to seek an economical and environmentally friendly technique. The use of plants in different ways such as potted plants or green walls is considered as a potential green solution for the improvement of indoor air quality and the health level of its inhabitants. A review of the literature cited in this paper suggests that plants absorb some of the pollutants, such as particles directly and remove some pollutants such as VOCs indirectly through biological transfer or by using microorganisms. This review paper discusses the types of plants that have been used for the phytoremediation of airborne pollutants and the routes and mechanisms for removing the pollutants. Removal pathways of the pollutants by aerial parts of the plants, the growth media along with the roots and their microorganisms in the rhizosphere part were also discussed. Sensitive analysis of extracted data from the literature outlined the most useful types of plants and the appropriate substrate for phytoremediation. Also, it showed that factors affecting the removal efficiency such as light intensity and ambient temperature, behave differently depending on pollutants and plants types.
... Widely used indoors, ornamental plants can indicate and monitor atmospheric pollutants (Cruz et al. 2014;Lin et al. 2017;Parseh et al. 2018). Volatile organic compounds (VOCs) are found in indoor air. ...
... Formaldehyde is the most common VOC emitted from household materials and is associated with health risks. As biological purifiers, Hedera helix L. plants, decreased by 70% the time required to reach 1.0 ppm of formaldehyde gas compared to natural dissipation (Lin et al. 2017), while Chamaedorea elegans Mart. removed 100% of the compound (16.4 mg m −3 ) in six days . ...
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Phytoremediation is an eco-friendly and economical technology in which plants are used for the removal of contaminants presents in the urban and rural environment. One of the challenges of the technique is the proper destination of the biomass of plants. In this context, the use of ornamental plants in areas under contamination treatment improves landscape, serving as a tourist option and source of income with high added value. In addition to their high stress tolerance, rapid growth, high biomass production, and good root development, ornamental species are not intended for animal and human food consumption, avoiding the introduction of contaminants into the food web in addition to improving the environments with aesthetic value. Furthermore, ornamental plants provide multiple ecosystem services, and promote human well-being, while contributing to the conservation of biodiversity. In this review, we summarized the main uses of ornamental plants in phytoremediation of contaminated soil, air, and water. We discuss the potential use of ornamental plants in constructed buffer strips aiming to mitigate the contamination of agricultural lands occurring in the vicinity of sources of contaminants. Moreover, we underlie the ecological and health benefits of the use of ornamental plants in urban and rural landscape projects. This study is expected to draw attention to a promising decontamination technology combined with the beautification of urban and rural areas as well as a possible alternative source of income and diversification in horticultural production. Graphical abstract
... Therefore, it is of great significance to develop efficient and stable HCHO scavenging technology for indoor air purification. At present, physical adsorption (Chen et al. 2017a;Falco et al. 2018), green planting (Chen et al. 2017b), ozone (Zhu et al. 2017a) and catalytic oxidation (Quiroz et al. 2013;Nie et al. 2016;Bai et al. 2016) are the widely applied methods to remove HCHO. Physical adsorption method is simple and easy to perform, but the performance of the adsorbent is not stable with issues of adsorption saturation and secondary pollution. ...
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Degradation of formaldehyde (HCHO) in interior decoration has been an urgent issue due to its toxicity nature and potential threats to human health. In this work, manganese dioxide nanoparticles (MnO2 NPs) were in situ grown on the polydopamine (pDA)-templated cotton fabrics for environmentally friendly HCHO degradation applications. The morphology, elemental composition, and crystal structure of the cotton/pDA/MnO2 were characterized by scanning electron microscopy–energy dispersive X-ray spectrum, Fourier transform infrared, X-ray diffractometer and X-ray photoelectron spectroscopy, respectively. The degradation of HCHO by the as-developed cotton/pDA/MnO2 was measured in a self-made quartz reactor, and the stability of adsorption was evaluated by cyclic experiments. The results showed that the HCHO removal efficiency reached to 100% within 20 min after three cycles, suggesting that the as-prepared fabrics exhibited good stability for the degradation of HCHO. The development of MnO2 NPs coated fabrics provides new strategies in degradation HCHO in interior decoration.
... Okrem znižovania výskytu mestských ostrovov tepla v sídelnej štruktúre, vegetačné prvky znižujú koncentráciu pevných častíc PM2,5 a PM10 v ovzduší. Dreviny a najmä stálozelené druhy dokážu prachové častice [10], [11] a prchavé organické zlúčeniny [12] zachytávať a znižovať výskyt v okolitom prostredí ovzdušia, v pôde a v prostredí interiérov. Pri pokusoch redukcie prachových častíc vplyvom druhov rodu Cupressaceae bol zistený pokles častíc PM2,5 o 20% v najefektívnejšej filtračnej schopnosti do 2 metrov od výšky koruny [13]. ...
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Urban structures influence the formation of natural processes, which results in an increased manifestation of the climate change and extreme weather conditions. The initial occurence of climate change occuring in the urban environment and in the landscape have supported the emergence of adaptation measures in response to climate change. Climate change is in the constant process of its development, but with the implementation of appropriate measures it is possible to partially mitigate and strategically adapted urban structures. Reduction of the negative microclimatic events of the urban environment can be achieved by supporting the system of green and blue infrastructure. In the case of Slovak City centers, it is possible to evaluate the diverse representation of blue-green infrastructure, which mainly depends on the hypsometry of the area. This research was focused on the analysis and comparison of the elements ensuring the ecological and microclimatic structure of urban structures. The analysis was applied Slovak cities with at least 1500 inhabitants per 1 km2 in city center and the total population in the city exceeding 50,000.
... Studies on the improvement effect of purification have been actively conducted on the reduction of indoor air pollutants by air purification plants [59,60]. For example, there was a study result that proved that the CH 2 O concentration was reduced when air purifying plants were planted indoors by conducting a closed experiment assuming outdoor air conditions in which natural ventilation is difficult in winter and early spring [61,62]. In addition, there is a study comparing the concentration of pollutants due to the decomposition of pollutants in indoor ventilation and photo plasma, and there is a study that the removal of pollutants is more effective than when the ventilation is performed twice and 1.3 times [63]. ...
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Children inhale indoor air at 400 mL/min∙kg per body weight, 2.76 times more than adults. They have weaker immunity than adults and are more exposed to asthma, allergies, and atopic diseases. The objective of this paper is to suggest effective management and improvement measures for indoor air quality for nurseries. As a methodology, 16 nurseries (total of 35 classrooms) were selected to measure the indoor air quality compared with WHO IAQ Standard, and identify the daily concentration change of the pollutants. Based on the measurements, IAQ improvements for selected facilities are carried out to compare the results before and after improvement. The result has shown that the concentration of Carbon Dioxide (CO2), Total Volatile Organic Compounds (TVOC), Total Suspended Particles (TSP) and formaldehyde (CH2O) exceeds WHO IAQ standards. The concentration of CO2 and TSP is changed mainly by physical activity of children and that of CH2O and TVOC is changed mainly by ventilation after school start. TVOC decreased by 46.4% and the TSP decreased by 21.7% after air purifier, but CH2O and TVOC increased 1.8–3.8 times after interior renovation with low-emission finishing materials. After new ventilation installation, the CH2O and TVOC reduced half and the TSP reduced one third. It is proven that the most effective way to reduce the concentration of air pollutants in nurseries is the installation of a new ventilation system, followed by an air purifier. The renovation with low-emission finishing materials cannot improve IAQ in a short period of time.
... Epipremnum aureum plant had a positive impact on mixed VOC (decane, toluene, 2 ethylhexanol, benzene, octane, xylene, α-pinene) filtration than Davallia fejeensis [58] Hedera helix Hedera helix reported a 70% reduction of the required time to reach 0.5 ppm of gaseous HCHO when compared with natural dissipation [76] on environmental factors such as temperature, humidity, and air pollutants [87,88]. Plant associated microflora plays a crucial role in VOC degradation by increasing the bioavailability of VOCs to plants via the production of biosurfactants and the formation of biofilms [89]. ...
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Indoor air pollution is a significant problem today because the release of various contaminants into the indoor air has created a major health threat for humans occupying indoors. Volatile Organic Compounds (VOCs) are pollutants released into the environment and persist in the atmosphere due to its low boiling point values. Various types of indoor activities, sources, and exposure to outdoor environments enhance indoor VOCs. This poor indoor air quality leads to adverse negative impacts on the people in the indoor environment. Many physical and chemical methods have been developed to remove or decompose these compounds from indoors. However, those methods are interrupted by many environmental and other factors in the indoor atmosphere, thus limit the applications. Therefore, there is a global need to develop an effective, promising, economical, and environmentally friendly alternatives to the problem. The use of the plant and associated microflora significantly impact reducing the environmental VOC gases, inorganic gases, particulate matter, and other pollutants contained in the air. Placing potted plants in indoor environments not only helps to remove indoor air pollutants but also to boost the mood, productivity, concentration, and creativity of the occupants and reduces stress, fatigue, sore throat, and cold. Plants normally uptake air pollutants through the roots and leaves, then metabolize, sequestrate, and excrete them. Plant-associated microorganisms help to degrade, detoxify, or sequestrate the pollutants, the air remediation, and promote plant growth. Further studies on the plant varieties and microorganisms help develop eco-friendly and environmentally friendly indoor air purifying sources.
Formaldehyde evolves from various household items and is of environmental and public health concern. Removal of this contaminant from the indoor air is of utmost importance and currently, various practices are in the field. Among these practices, indoor plants are of particular importance because they help in controlling indoor temperature, moisture, and oxygen concentration. Plants and plant materials studied for the purpose have been reviewed hereunder. The main topics of the review are, mechanism of phytoremediation, plants and their benefits, plant material in formaldehyde remediation, and airtight environmental and health issues. Future research in the field is also highlighted which will help new researches to plan for the remediation of formaldehyde in indoor air. The remediation capacity of several plants has been tabulated and compared, which gives easy access to assess various plants for remediation of the target pollutant. Challenges and issues in the phytoremediation of formaldehyde are also discussed. Novelty statement: Phytoremediation is a well-known technique to mitigate various organic and inorganic pollutants. The technique has been used by various researchers for maintaining indoor air quality but its efficiency under real-world conditions and human activities is still a question and is vastly affected relative to laboratory conditions. Several modifications in the field are in progress, here in this review article we have summarized and highlighted new directions in the field which could be a better solution to the problem in the future.
Indoor air quality is of emerging importance due to the rapid growth of urban populations that spend the majority of their time indoors. Amongst the public, there is a common perception that potted-plants can clean the air of pollutants. Many laboratory-based studies have demonstrated air pollution phytoremediation with potted-plants. It has, however, been difficult to extrapolate these removal efficiencies to the built environment and, contrary to popular belief, it is likely that potted-plants could make a negligible contribution to built environment air quality. To overcome this problem, active green walls have been developed which use plants aligned vertically and the addition of active airflow to process a greater volume of air. Although a variety of designs have been devised, this technology is generally capable of cleaning a variety of air pollutants to the extent where comparisons against conventional air filtration technology can be made. The current work discusses the history and evolution of air phytoremediation systems from potted-plants through to practical botanical air filtration.
An indoor formaldehyde enriched environment was created by an automatic fumigation system with timing and concentration control. Selected hydroponic plant species were exposed in formaldehyde concentrations of 10 mg m⁻³, 50 mg m⁻³ and 100 mg m⁻³ respectively for 6 days with 10-h-treatment each day. Changes in morphological characteristics including leaf damage rate, leaf damage time and survival rate were monitored to evaluate morphological resistance to formaldehyde. Assessed physiological parameters were leaf chlorophyll content (Chl), leaf malondialdehyde content (MDA), activity of leaf formaldehyde dehydrogenase (FADH), leaf water soluble sugar content (WSS), and leaf proline content (Pro). Under formaldehyde suppression, reduction of Chl and increase of MDA and Pro were observed. Varying by species, FADH and WSS peaked at certain formaldehyde concentrations. A Principal Component Analysis (PCA) method was adopted to evaluate key factors in hydroponic plants' tolerance to formaldehyde. Among the 15 species selected, the best 5 performing species are Spathiphyllum floribundum, Alocasia cucullata, Davallia bullata, Syngonium podophyllum ‘Pixie’, and Schefflera octophylla. The study helps people to select the best ornamental plants for indoor air pollution control. The response of hydroponic plant species to formaldehyde was studied for eco-friendly indoor air pollution control.
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Controllable nanoporous hematite (CNH, α-Fe2O3) was prepared by thermal treatment of α-FeOOH at different temperatures, and the SCR activity of the prepared α-Fe2O3 was evaluated. XRD (X-ray diffraction), HRTEM (high-resolution transmission electron microscopy), N2 adsorption-desorption, XPS (X-ray photoelectron spectroscopy), and NH3-TPD (NH3-temperature programmed desorption) were utilized to characterize the catalysts. The results indicated that after thermal treatment at less than 600°C, the α-Fe2O3 catalysts exhibited excellent NO conversion that was higher than 80% in a temperature range from 300 to 400°C. CNH400 with a relatively large surface area of 47.24 m² g–1 and many surface hydroxyl groups did not exhibit a substantially improved SCR activity even though it exhibited the best SCR activity. Therefore, the L-H mechanism was not the main reaction route for SCR of NO by α-Fe2O3. The increasing crystallization of α-Fe2O3 decreased the SCR activity, indicating that a decrease in surface oxygen defects was important for the SCR of NO and fitting the E-R mechanism. The NH3-TPD and XPS (O1s) results confirmed this hypothesis. This study provides an approach for the design and preparation of a controllable nanoporous α-Fe2O3 catalyst for SCR of NO by NH3.
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he extreme weather conditions in Middle East Area led to the construction of tightly sealed, air conditioned buildings, characterized by indoor air quality deterioration. This study presents the results of chemical characterization of outdoor and indoor PM 2.5 and PM 10 in Doha city, over a two-month period including normal days and dust events, aiming at identifying the factors affecting the indoor air of an office building. The WHO guideline values were exceeded in 100% of the outdoor measurements. 49% of the days of the sampling campaign were characterized as non-dusty (PM 10 < 200 µg m –3), 49% as minor-dusty (200 < PM 10 < 1000 µg m –3) while in one case (2%) there was a major-dusty day (PM 10 > 1000 µg m –3). The contribution of both dust and anthropogenic emissions sources is depicted in particles' mass and chemical composition. The elevated –especially outdoor-levels of carbonate carbon indicate the presence of crustal matter originating from the surrounding crustal material. OC/EC values reveal possible combined contribution from secondary organic aerosol, traffic-related sources and re-suspended dust. The influence of anthropogenic emissions is implied by the predominance of nitrate and sulfate ions, which constitute a substantial percentage of the particle mass. The crustal origin of particles is also depicted in metals. However, the higher enrichment factor values which may imply anthropogenic activities of both the outdoor and indoor environment were determined sequentially for Cd, Pb, As, Cu and Zn, suggesting the role of infiltration. Concluding, the indoor to outdoor relationship is significantly influenced by particles infiltration and penetration into the building mainly through the ventilation system and to a lesser extent, through windows or cracks in the building envelope. Although the low indoor to outdoor ratio underlies the predominance of outdoor levels compared to the indoor ones, there is positive correlation between indoor and outdoor PM, during the days that the building was open to the public and employees.
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In 2010, the World Health Organization (WHO) established an indoor air quality guideline for short- and long-term exposures to formaldehyde (FA) of 0.1 mg/m(3) (0.08 ppm) for all 30-min periods at lifelong exposure. This guideline was supported by studies from 2010 to 2013. Since 2013, new key studies have been published and key cancer cohorts have been updated, which we have evaluated and compared with the WHO guideline. FA is genotoxic, causing DNA adduct formation, and has a clastogenic effect; exposure-response relationships were nonlinear. Relevant genetic polymorphisms were not identified. Normal indoor air FA concentrations do not pass beyond the respiratory epithelium, and therefore FA's direct effects are limited to portal-of-entry effects. However, systemic effects have been observed in rats and mice, which may be due to secondary effects as airway inflammation and (sensory) irritation of eyes and the upper airways, which inter alia decreases respiratory ventilation. Both secondary effects are prevented at the guideline level. Nasopharyngeal cancer and leukaemia were observed inconsistently among studies; new updates of the US National Cancer Institute (NCI) cohort confirmed that the relative risk was not increased with mean FA exposures below 1 ppm and peak exposures below 4 ppm. Hodgkin's lymphoma, not observed in the other studies reviewed and not considered FA dependent, was increased in the NCI cohort at a mean concentration ≥0.6 mg/m(3) and at peak exposures ≥2.5 mg/m(3); both levels are above the WHO guideline. Overall, the credibility of the WHO guideline has not been challenged by new studies.
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This study was conducted to evaluate the ability of plants to purify indoor air by observing the effective reduction rate among pollutant types of particulate matter and volatile organic compounds. Particulate matter and four types of volatile organic compounds were measured in a new building that is less than 3 years old and under three different conditions: before applying the plant, after applying the plant, and a room without a plant. The removal rate of each pollutant type due to the plant was also compared and analyzed. In the case of indoor particulate matter, the removal effect was negligible because of outdoor influence. However, 9% of benzene, 75% of ethylbenzene, 72% of xylene, 75% of styrene, 50% of formaldehyde, 36% of acetaldehyde, 35% of acrolein with acetone, and 85% of toluene were reduced. The purification of indoor air by natural ventilation is meaningless because the ambient particulate matter concentration has recently been high. However, contamination by gaseous materials such as volatile organic compounds can effectively be removed through the application of plants.
To investigate the indoor air quality (IAQ) over Xi’an, the concentrations of volatile organic compounds (VOCs, including formaldehyde, benzene, toluene, o-xylene, p-xylene, n-butyl acetate, ethylbenzene, styrene, n-undecane, and total VOCs) in 471 residential rooms and 58 public rooms during 2014–2015 were determined. All the data were measured at a variety of 6–48 months after the decorations of these rooms. The results showed that formaldehyde was the most serious pollutant in almost all the monitored rooms. The concentrations of formaldehyde in residences and public places ranged from 0.02 mg m–3 to 0.45 mg m–3 and 0.05 mg m–3 to 0.32 mg m–3, respectively. And the concentration levels in the 83.6% selected residences and 44.8% public places exceeded the Chinese National Indoor Air Quality Standard (GB/T 18883-2002) of formaldehyde value (0.1 mg m–3). However, the TVOC concentrations in most sites were lower than the Chinese National Standard (GB/T 18883–2002) value. In residences, the formaldehyde and TVOC concentrations in bedrooms were slightly higher than those in living rooms and other rooms. The relationships among formaldehyde and TVOC concentrations with indoor temperature, relative humidity (RH), and decorative materials (curtain, wall decoration, wood floor, and panel furniture) were also investigated. Formaldehyde levels showed strong positive correlation with indoor temperature and RH. However, the TVOC levels had a relatively weak correlation with indoor air temperature and RH. The wall decoration and panel furniture were the main sources of indoor formaldehyde, while wood floor and panel furniture were the main sources of TVOC. In addition, indoor air pollution of three selected newly decorated houses with 11 rooms was monitored monthly for one year to evaluate the relationship between indoor pollution levels and ventilation time. It was found that the concentrations of formaldehyde and TVOC decreased with ventilation time, and the duration was one year after decoration especially after summer ventilation.
Human exposure to volatile organic compounds (VOCs) indoors is receiving increasing attention. Formaldehyde (HCHO) is the most common VOC emitted from household materials and is associated with many health risks, including sick building syndrome. In this study, a simple box model was developed and applied to help understand the fate and degradation mechanisms of HCHO in the indoor environment. The model was validated using observations from an air handling system under different conditions. A UV/TiO2 filter reactor was installed in a closed box with the air conditioning unit. Three parameters, temperature, relative humidity, and circulation wind speed, were investigated for their effects on the performance of the air handling system. Our results show that the operation mode of the air handling system has a greater effect on the removal of HCHO than any of the air conditioning parameters. From a kinetic perspective, the removal of gaseous HCHO from a constant-volume box clearly represents a zero-order reaction. After UV irradiation with a TiO2 filter for 2 hours, the removal efficiency of gaseous HCHO increases to approximately 90%. Contributions to the removal of gaseous HCHO from natural dissipation, photodegradation, and photocatalytic oxidation decomposition are 12%, 30%, and 58%, respectively. Our results have implications for reducing indoor air pollution and reducing stress on air conditioning systems. Meeting these goals is beneficial for human health and energy conservation in modern society.
CeO2-MoO3/TiO2 catalysts were prepared by three methods: a single step sol-gel (SG), impregnation (IM) and coprecipitation (CP) method. These catalysts were investigated for selective catalytic reduction (SCR) of NO with NH3. The results indicate that the catalyst prepared by the SG method possessed the widest temperature window (about 250– 475°C), best SCR activity below 450°C and resistance against 10% H2O and 1000 ppm SO2 at a gas hourly space velocity (GHSV) of 90,000 h–1. According to the results of BET, XRD, XPS, H2-TPR and TEM, it is found that larger BET surface area, more highly dispersed active species of Ce and Mo, presence of more Ce³⁺ and chemisorbed oxygen, synergistic effect among ceria, molybdenum and titania, and better redox ability can contribute to the better deNOx performance of the CeO2-MoO3/TiO2 catalyst prepared by the SG method, compared with those by the IM and CP methods.
Air pollution due to PM2.5 is of public concern in Korea. Ambient PM2.5 can penetrate indoors through the building envelope, affecting the indoor PM2.5 concentrations. Most people stay indoors for approximately 80% of every day, implying that their primary exposure to PM2.5 could be determined by the indoor air. This study aims to investigate the infiltration of ambient PM2.5 through the building envelop in apartment housing units in Korea. The on-site infiltration test method, by using a blower-door depressurization procedure, was suggested in order to maintain an identical indooroutdoor pressure difference among the tests. On-site experiments were conducted in 11 apartment housing units to estimate the PM2.5 infiltration factors. The results showed that the average infiltration factor of all the test housing units was 0.65 ± 0.13 (average ± standard deviation), with a minimum of 0.38 and a maximum of 0.88. Furthermore, the results from the relation of the building airtightness data to the infiltration factors suggests that a leaky housing unit with high ACH50, or a high specific effective leakage area (ELA), would be more significantly influenced by the ambient PM2.5. The study demonstrated that the suggested infiltration test procedure was useful to assess the infiltration factors in conditions of controlled indoor-outdoor pressure differences in real housing units.
The scientific articles and Indoor Air conference publications of the indoor air sciences (IAS) during the last 50 years are summarized. In total 7524 presentations, from 79 countries, have been made at Indoor Air conferences held between 1978 (49 presentations) and 2014 (1049 presentations). In the Web of Science 26,992 articles on indoor air research (with the word "indoor" as a search term) have been found (as of 1 Jan 2016) of which 70% were published during the last 10 years. The modern scientific history started in the 1970s with a question: "did indoor air pose a threat to health as did outdoor air?" Soon it was recognized that indoor air is more important, from a health point of view, than outdoor air. Topics of concern were first radon, environmental tobacco smoke and lung cancer, followed by volatile organic compounds, formaldehyde and sick building syndrome, house dust mites, asthma and allergies, Legionnaires disease and other airborne infections. Later emerged dampness/mold-associated allergies and today's concern with "modern exposures-modern diseases." Ventilation, thermal comfort, indoor air chemistry, semi volatile organic compounds, building simulation by computational fluid dynamics, and fine particulate matter are common topics today. From their beginning in Denmark and Sweden, then in the USA, the indoor air sciences now show increasing activity in East and Southeast Asia. This article is protected by copyright. All rights reserved.
To identify the sources of PM2.5 pollutants in work environments and determine whether the air quality inside an office was affected by a change in outdoor pollution status, concurrent indoor and outdoor measurements of PM2.5 were conducted at five different office spaces in the urban center of Guangzhou on low pollution days (non-episode days, NEDs), and high pollution days (haze episode days, EDs). Indoor-outdoor relationships between the PM2.5 mass and its chemical constituents, which included water-soluble ions, carbonaceous species, and metal elements, were investigated. A principle component analysis (PCA) was performed to further confirm the relationship between the indoor and outdoor PM2.5 pollution. The results reveal that (1) Printing and ETS (Environmental tobacco smoking) were found to be important office PM2.5 sources and associated with the enrichment of SO4²⁻, OC, EC and some toxic metals indoors; (2) On EDs, serious outdoor pollution and higher air exchange rate greatly affected all studied office environments, masking the original differences of the indoor characteristics (3) Fresh air system could efficiently filter out most of the outside pollutants on both NEDs and EDs. Overall, the results of our study suggest that improper human behavior is associated with the day-to-day generation of indoor PM2.5 levels and sporadic outdoor pollution events can lead to poor indoor air quality in urban office environments. Moreover, fresh air system has been experimentally proved with data as an effective way to improve the air quality in office.