The Influence of House Plants on Indoor CO2

Abstract

This study aimed at determining the effect of carbon dioxide (CO2) in the internal environment of different indoor plants. Spathiphyllum (Spathiphyllum floribundum Schott), Yucca (Yucca elephantipes Regel), Dieffenbachia (Dieffenbachia amoena Gentil), and Ficus (Ficus benjamina L.) are frequently used in studies of indoor plants that examine light temperature depending on leaf surface and the effects of CO2 in the studied environment. As a result, decreases in CO2 were at the highest level in Ficus, and Dieffenbachia at 25°C, followed by Spathiphyllum at 25°C and Yucca at 20°C. The amount of photosynthesis increased the leaf surface. For this reason, they reduced the amount of CO2 by increasing the amount of photosynthesis. The plant leaf surface was standardized, and calculations were made to meet the objective and the amount of CO2 in the local environment. Based on these calculations, it was determined that the greatest reduction of CO2 comes from the Ficus plant. In conclusion, the same layer as the surface are 1 m2 leaf surface from Ficus benjamina on 1 m3 without air vent in which the amount of CO2 in one hour could be reduced to about the level from 2,000 ppm at 25°C 480.74 ppm and 408.08 ppm at 20°C.

Full text

Introduction
The recent rise in urbanization has led to increased
population density, particularly in urban areas. Hence the
number of people per unit area has increased. Nowadays,
urban people spend at least 80% of their lives in indoor
environments because of increased housing and changing
life conditions [1-3].
Rapid urbanization and industrialization have placed
more distance between people and nature each day.
This situation disrupts the harmony that is expected to
exist between people and their environment. Human
beings, as part of nature, carry with them a part of nature
wherever they live. This has sometimes been in the form
of a houseplant, a small garden, or sometimes a delicately
organized park [3-5].
Plants that exist particularly in indoor environments,
where people spend more than 80% of their lives, undertake
many ecological and aesthetical functions. Indoor plants
reduce all kinds of air pollution [6], increase productivity
[7], relieve people psychologically, and minimize stress
and negative feelings [3]. Previous studies have reported
that the presence of plants in indoor environments reduces
diseases and absenteeism [3, 8].
Pol. J. Environ. Stud. Vol. 26, No. 4 (2017), 1643-1651
Original Research
The Inuence of House Plants on Indoor CO2
Hakan Sevik1, Mehmet Cetin2*, Kerim Guney3, Nur Belkayali2
1Kastamonu University, Faculty of Engineering and Architecture, Department of Environmental Engineering,
37150, Kastamonu, Turkey
2Kastamonu University, Faculty of Engineering and Architecture, Department of Landscape Architecture,
37150, Kastamonu, Turkey
3Kastamonu University, Faculty of Forestry, Department of Forest Engineering,
37150, Kastamonu, Turkey
Received: 13 December 2016
Accepted: 8 February 2017
Abstract
This study aimed at determining the effect of carbon dioxide (CO2) in the internal environment of
different indoor plants. Spathiphyllum (Spathiphyllum floribundum Schott), Yucca (Yucca elephantipes
Regel), Dieffenbachia (Dieffenbachia amoena Gentil), and Ficus (Ficus benjamina L.) are frequently used
in studies of indoor plants that examine light temperature depending on leaf surface and the effects of CO2
in the studied environment. As a result, decreases in CO2 were at the highest level in Ficus, and
Dieffenbachia at 25ºC, followed by Spathiphyllum at 25ºC and Yucca at 20ºC. The amount of photosynthesis
increased the leaf surface. For this reason, they reduced the amount of CO2 by increasing the amount of
photosynthesis. The plant leaf surface was standardized, and calculations were made to meet the objective
and the amount of CO2 in the local environment. Based on these calculations, it was determined that the
greatest reduction of CO2 comes from the Ficus plant. In conclusion, the same layer as the surface are 1 m2
leaf surface from Ficus benjamina on 1 m3 without air vent in which the amount of CO2 in one hour could
be reduced to about the level from 2,000 ppm at 25ºC 480.74 ppm and 408.08 ppm at 20ºC.
Keywords: CO2, plant, indoor, air quality, indoor plants, leaf surface
*e-mail: mehmet.cetin@temple.edu
DOI: 10.15244/pjoes/68875

1644 Sevik H., et al.
One of the most important reasons plants are wanted in
indoor environments is their inuence on carbon dioxide
(CO2). CO2 is one of the gases the composition of which
changes in indoor environments in the fastest way as a
result of human metabolic activities. The composition of
air with 21% oxygen (O2) and 0.033% CO2 when inhaled
from the normal atmosphere turns to have an O2 level of
16-17% and a CO2 level of 4% when exhaled from the
lungs. This change leads to a rapid increase in CO2 amount,
particularly in environments such as schools, malls, and
hospitals, where people are collectively active [9]. When
the rate of CO2 increases in an environment, this leads to
fatigue, difculty in perception, and sleepiness [10]. When
the amount of CO2 exceeds 1,000 ppm, headache, vertigo,
fatigue, concentration disorders, and smell disorders may
be experienced. When it exceeds 1,500 ppm, it results
in irritation in throat and nose, nasal ow, cough, and
eye drainage [11]. This is particularly evident in indoor
environments where the majority of daily life is spent.
The reduction in indoor air quality inuences people’s
performance and health [10].
According to the authorities, air quality can be
regarded as harmless if CO2 levels are below 1,000
ppm, elevated if between 1,000 and 2,000 ppm, and
hygienically unacceptable if above 2,000 ppm [12].
However, previous studies have shown that CO2 amounts
have reached 4,000 ppm in schools [13] and 2,500 ppm in
ofces [14].
The most inuential way to reduce CO2 in an
environment is ventilation. Indeed, outdoor air can be 5 to
100 times as clear as indoor air [9]. However, even a short
period of ventilation leads to a considerable loss of heat in
the environment, particularly in winter months, leading to
inadequate ventilation in indoor environments.
Another way to reduce CO2 in indoor environments is
by using plants. Plants photosynthesize in environments
where light and heat are adequate as part of their natural
life process. They absorb the CO2 in the environment
through their stomas for photosynthesis. Hence, they
use CO2 for photosynthesis, leading to a reduction in its
amount in the environment. However, plants are also
living organisms and need certain conditions to survive.
They also change environmental conditions through their
metabolic activities. Plants emit oxygen and absorb CO2
when environmental conditions are suitable for their
growth. When conditions change, the situation becomes
reverse. This may result in negative inuences on human
health, particularly in indoor environments that are
limited. Obviously, environmental conditions for each
plant to survive change. Even when the conditions are
optimal, plants may have different photosynthesis rates
and thus have varying degrees of inuence on indoor
CO2 amounts. Therefore, plants can be effectively used
to maintain healthy conditions regarding CO2 amounts in
indoor environments where people spend most of their
lives if one detects to what extent indoor conditions are
suitable for plants, under which conditions the metabolic
activities of plants inuence indoor CO2 amounts, and
what kind of inuence they have.
The purpose of this study is to reveal the inuence of
certain plant species that can be used as indoor plants on
indoor CO2 amounts. The study focuses on the changes
made by plants on CO2 amounts at various temperature
levels. To this end, four different indoor plants were
selected to determine how they change indoor CO2
amounts at ve different leaf surfaces, ve different
temperature levels, and under 20,000 lux light and dark
conditions.
Material and Methods
This study focuses on the inuence of certain frequen-
tly used indoor ornamental plants on CO2 amounts in
indoor environments. In this sense, Spathiphyllum
(Spathiphyllum floribundum Schott), Yucca (Yucca
elephantipes Regel), Dieffenbachia (Dieffenbachia
amoena Gentil), and Ficus (Ficus benjamina L.), which
are common indoor plants, constitute the study material.
These plants differ from one another in terms of ecological
demands and physical characteristics (e.g., leaf area and
body shape).
The study was conducted in a plant growth chamber
that was not in contact with outdoor air and whose
internal volume was known. The light and temperature
conditions of the chamber were determined independent
of the outdoor environment. In addition to the plant, a
measurement device that can regularly measure CO2,
temperature, and humidity and transfer measurements to
the computer was placed in the plant growth chamber.
Particular attention was paid to plants’ being healthy,
having a proper root/body ratio, and not being exposed
to any stress factor. Therefore, the pots of the procured
plants were changed in the rst place so that root/body
ratio could be increased in favor of the roots.
The plant growth chamber in which the study
conditions were provided was of the Jaiotech GC 300
brand. This plant growth chamber produces 20,000 lux
light when all the lights are turned on, and its temperature
can be set with a precision of 1°C (equipped with a heating
and cooling system). It also has a CO2 tank to increase
environmental CO2. It can periodically be programmed to
maintain the required conditions.
Given that the study was based on absolute tightness,
a glass chamber whose air tightness had been tested was
placed inside the chamber. An Extech desktop indoor
air quality CO2 data logger was placed inside this glass
chamber. This device is used for CO2 measurements and is
capable of measuring at 1 ppm precision. This CO2 meter
was calibrated prior to being used. It was also tested for its
CO2 tightness, and it was ensured that there would be no
air intake or outlet.
The plants were placed inside the chamber for
measurements. The CO2 amount inside the chamber was
set to 2,000 ppm ±10%. The initial CO2 amount was set
to be 2,000 ppm because plants generally reach
maximum photosynthesis speed at levels higher than
1,200-1,300 ppm. Furthermore, previous studies on

1645
The Influence of House...
indoor air quality have demonstrated that indoor CO2
amount reaches 2,000 ppm in environments where people
are collectively active in a short period [15-16].
Raising the CO2 amount to 2,000 ppm ±200 ppm level
was performed through respiration into the device for a few
minutes. The CO2 amount in the air exhaled was around
40,000 ppm following human respiration. Therefore,
respiring in the chamber where the plant was placed
increased the CO2 amount to the required level in a short
period. However, the CO2 amount became homogenized
and stable in the air after a while. Therefore, at least
10 minutes passed before the chamber was closed. When
the CO2 amount reached the required level, the chamber
was closed with an absolute tightness. Meanwhile, when
the CO2 amount was higher than required, the chamber
was ventilated; and when it was lower than required,
respiration was repeated to obtain the required CO2
amount.
This study seeks to reveal the inuences of plants on
CO2 amount in illuminated and dark environments. The
selected amount of light was 20,000 lux.
The plants that were prepared for the measurements
were placed inside the chamber. The measurement order
of the chamber is as follows:
– 15ºC degrees, 20,000 lux light, 12 hours
– 15ºC degrees, dark environment, 12 hours
– 20ºC degrees, 20,000 lux light, 12 hours
– 20ºC degrees, dark environment, 12 hours
– 25ºC degrees, 20,000 lux light, 12 hours
– 25ºC degrees, dark environment, 12 hours
– 30ºC degrees, 20,000 lux light, 12 hours
– 30ºC degrees, dark environment, 12 hours
– 35ºC degrees, 20,000 lux light, 12 hours
– 35ºC degrees, dark environment, 12 hours
Keeping the plants in the light for 12 hours and in
the dark for 12 hours is about simulating the environ-
ment that plants are used to as much as possible. Plants
stay in the light and stay in the dark for a certain period
every day. The measurements were planned in this manner
to avoid disturbing the order the plants were used to.
The device was set as explained above. The plant was
then placed inside the chamber within the device. The
measurement device inside the same environment as the
plant was started in such a way that it would measure
every ve minutes and record the data, and the chamber
was closed tightly.
The data were transferred to the computer after the
measurement ended. The net volume of the chamber was
calculated (by subtracting the volume of the pot and the
body volumes of Yucca, Ficus, and Dieffenbachia from
the volume of the chamber).
The purpose was to show the performances of the
plants at the end of an hour. However, considering that the
measurement device would be stable only after a while
and the time it would take for the plants to get used to
the values in the environment they were put in, the plants
were placed inside the chamber at least one hour before
starting the measurement. Hence, the measurement results
that were obtained at least one hour after the plants were
placed were considered for a sound measurement. Each
plant remained inside the chamber for ve days after being
placed in it. The device was operated in that period with
the settings specied above. The CO2 measurement device
performed measurements every ve minutes. Afterward,
the data were transferred to the computer for assessment.
As data evaluation dealt with the plant performances
at the end of an hour and the values obtained at least
one hour after the placement of the plants inside the
chamber were considered for a sound measurement, the
measurements that were performed while the chamber
was making transitions between the programs were also
ignored. For instance, while the climate chamber was
transiting from the program of 12 hours in the dark with
20ºC to the program of 12 hours in the light with 25ºC,
plant performance was ignored for one hour. The values
obtained at the end of this process were considered.
Hence, 10 measurements were carried out with each
one lasting one hour through a device that operated for
12 hours. The data were obtained by calculating the
difference between the initial CO2 values and the values
at the end of one hour.
This study aimed to reveal the inuences of ve
different leaf surfaces on CO2 amount. Therefore, after
performing the initial measurements, approximately 1/5 of
the plant leaves were cut to calculate the leaf area. In the
next period, 1/4 of the leaf area was cut, followed by 1/3
and ½, so that nearly 1/5 of the initial leaf area was cut in
each period. However, leaf cutting was performed based
on estimations, and the leaf area was calculated after being
cut.
After obtaining the data, they were standardized to
determine which leaf surface had the most inuence on
1 m3 of air as well as the degree of such inuence. The
plant growth chamber’s capacity is 70 x 70 x 110 cm. The
total of volume is 0.539 m3. For instance, assuming that
in a chamber with a volume of 0.486 m3 (after subtracting
the volume of the pot), Ficus having 0.245 m2 leaf area
reduced CO2 by 157 ppm in an hour. While assessing these
data, a calculation was made based on the equation that
the CO2 amount in an area of 1 m3 is reduced by 157 ppm
by Ficus having x m2 leaf area assuming that Ficus having
0.245 m2 leaf area reduced the CO2 amount by 157 ppm
in an area of 0.486 m3. Hence, it was recorded as follows:
“Ficus having a leaf area of 0.504 m2 reduces the CO2
amount in an area of 1 m3 by 157 ppm in one hour.” This
means the differences that stemmed from the pot sizes
were eliminated.
While calculating the net volume of the chamber,
only the volumes of Yucca, Ficus, and Dieffenbachia
were considered because their body volumes could be
calculated. The volumes of the leaves were ignored. The
measurements indicated that leaf thickness did not even
reach 2 mm in any of the studied species. When the leaf
volume is calculated, for instance, assuming that Ficus
having a leaf area of 0.245 m2 has a leaf thickness of
2 mm (the leaf thickness of Ficus is lower than
1 mm), the leaf volume calculated will be 0.245 m2*
0.002 m = 0.00049 m3. In a chamber having a net volume

1646 Sevik H., et al.
of 0.486 m3 (after subtracting the volumes of the pot and
the plant body), a leaf volume of 0.00049 m3 corresponds
to nearly 1/1000 of the chamber volume. The study
considered that ignoring the leaf volume would not affect
the results as leaf volume, when roughly calculated, did
not even reach 1/1000 of the total chamber volume. As a
result, leaf volume was ignored.
Hence, measurements of the study were performed in
200 combinations involving:
– Four different species (Spathiphyllum, Yucca,
Dieffenbachia, and Ficus).
– Two different light conditions (20,000 lux light and
dark).
– Five different degrees of temperature (15, 20, 25, 30,
and 35ºC).
– Five leaf surfaces.
Each measurement was repeated at least 10 times.
Thus an attempt was made to ensure that measurement
would be performed for 2,000 hours total. However, the
measurements were performed for 1,990 hours because
performing measurements with Spathiphyllum in the dark
at 35ºC was not possible.
20,000 lux light on species
Ficus Dieffenbachia Spathiphyllum Yucca
Temperature
Leaf
Surface
(m2)
Average*
(reduction of
CO2 per hour)
Leaf
Surface
(m2)
Average*
(reduction of
CO2 per hour)
Leaf
Surface
(m2)
Average*
(reduction of
CO2 per hour)
Leaf
Surface
(m2)
Average*
(reduction of
CO2 per hour)
15°C
0.185 -7.8 0.192 -6 0.336 -9.8 0.1395 -1.2
0.403 -15.2 0.384 -10.5 0.426 -15.9 0.298 -1.6
0.514 -21.1 0.469 -12.5 0.516 -13.8 0.509 -3.5
0.726 -28.9 0.628 -16.3 0.712 -20.9 0.745 -3.8
0.806 -40.2 0.747 -25.6 1.038 -40 0.837 -6
20°C
0.185 -75.9 0.192 -56.8 0.336 -75.9 0.1395 -22
0.403 -163.4 0.384 -109.3 0.426 -110.3 0.298 -56.7
0.514 -212.4 0.469 -116.3 0.516 -112.6 0.509 -71.7
0.726 -299.9 0.628 -179.3 0.712 -129.3 0.745 -154.8
0.806 -321 0.747 -187.9 1.038 -228.7 0.837 -120
25°C
0.185 -87.8 0.192 -61.6 0.336 -146.9 0.1395 -15.5
0.403 -192.9 0.384 -125.6 0.426 -191.2 0.298 -33.2
0.514 -250.1 0.469 -152.5 0.516 -193.3 0.509 -38.9
0.726 -332.5 0.628 -197.3 0.712 -254.1 0.745 -74
0.806 -407.6 0.747 -216.5 1.038 -361.2 0.837 -61
30°C
0.185 -43.7 0.192 -15.5 0.336 -54.6 0.1395 -7.1
0.403 -94.6 0.384 -31.6 0.426 -54.5 0.298 -15.5
0.514 -132.8 0.469 -40.3 0.516 -55.3 0.509 -24.2
0.726 -183.8 0.628 -48.6 0.712 -62.5 0.745 -37.8
0.806 -197.5 0.747 -58.3 1.038 -139.1 0.837 -46.2
35°C
0.185 -40 0.192 0.7 0.336 -2.9 0.1395 -3.3
0.403 -87.4 0.384 1.5 0.426 -7 0.298 -6.8
0.514 -112.8 0.469 3.1 0.516 -7.6 0.509 -11.1
0.726 -157.4 0.628 3.6 0.712 -5.2 0.745 -17.7
0.806 -172.4 0.747 3.3 1.038 -5.6 0.837 -17.1
*Mean average is reduction of CO2 per hour
Table 1. Effect of CO2 amount by the plants having different leaf surfaces under 20,000 lux light depending on temperature.

1647
The Influence of House...
Results and Discussion
In the end, the extent to which the CO2 amount was
reduced by the plants having different leaf surfaces under
20,000 lux light was dependent on the temperature. The
results are shown in Table 1.
The values in Table 1 show how many ppm the plants
having the specied leaf surfaces reduced the CO2 amount
in one hour from nearly 2,000 ppm under 20,000 lux light
condition. In the experiments conducted under 20,000 lux,
all the species excluding Dieffenbachia reduced the CO2
amount at all temperature levels. However, Dieffenbachia
increased the CO2 amount in the environment at 35ºC.
In addition, deformations were observed in the leaves at
this temperature. The plant that had the highest inuence
on CO2 amount in the environment was Ficus, having a
leaf surface of 0.806 m2. It reduced the CO2 amount in the
environment by -407.6 ppm at 25ºC and by -321 ppm at
20°C. However, the values in the table indicate that the
difference between the leaf surfaces could be deceptive.
Hence, the data were standardized. The inuence of each
plant having a leaf surface of 1 m2 on the CO2 amount in
the environment was calculated. The relevant results are
shown in Table 2.
The values in Table 2 show that only Dieffenbachia
increased the CO2 amount at 35ºC. All the other species
reduced the CO2 amount in the illuminated environment at
all temperature levels. However, the amount of reduction
signicantly varied from species to species. Of the species
having 1 m2 leaf surface, the one that reduced CO2 most
in 1 m3 of air was Ficus (by 480.74 ppm). This reduction
occurred at 25ºC. The next biggest reduction was observed
again with Ficus at 20ºC (by 408.08 ppm). The highest
reduction occurred at 25ºC for all the species, excluding
Yucca. The highest reduction was observed at 20ºC for
Yucca.
Calculations were made to reveal to what extent the
CO2 amount was raised in the dark by the plants having
different leaf surfaces depending on temperature. The
relevant results are shown in Table 3.
The results in Table 3 show that all the species
increased the CO2 amount in the environment at all
temperature levels. However, Dieffenbachia underwent
a deformation in its leaves at 35ºC. The values in Table
3 indicate that the plant that increased the CO2 amount
in the environment at the highest level was Spathiphyllum
at 25ºC. Spathiphyllum, having a leaf surface of
1.038 m2, increased the CO2 amount by 122.5 ppm in one
hour. Ficus, having a leaf surface of 0.806 m2, increased
the CO2 amount in the environment by 87.8 ppm in one
hour at 35ºC. To make a clearer comparison between
the species, we calculated how much the plants having
1 m2 leaf surface increased the CO2 amount at different
temperature levels in the dark. The relevant results are
presented in Table 4.
The values in Table 4 show that the CO2 amount
increased at all temperature levels. This, indeed, is a
quite natural result. Plants photosynthesize only in the
illuminated environments and can reduce CO2 there. In
the dark, however, they perform respiration and increase
the CO2 amount in the environment. The analyses indi-
cated that the plant that caused the highest increase in
CO2 was Spathiphyllum at 25ºC. Spathiphyllum and its
1 m2 leaf surface increased the CO2 amount in 1 m3 air
by 129.62 ppm in one hour. The second highest increase
was caused by Ficus at 35ºC. Given that Spathiphyllum
was damaged at 35ºC in the illuminated environment, its
inuence on the CO2 amount at 35ºC in the dark could not
be calculated.
The results show that plants change indoor CO2
amounts differently in the illuminated environment. In
general, the inuence of plants on CO2 amount increases
depending on temperature. It reaches a peak at a certain
level and then starts to decrease because of increasing
temperature. In other words, it makes a bell-shaped curve.
Kacar et al. [17] stated that the inuence of temperature
on photosynthesis in plant leaves generally makes a curve.
Speed of photosynthesis increases with the temperature
until a certain level, whereas photosynthesis rapidly
decreases after a certain temperature. This is reported by
many researchers [18].
However, the temperature level required for the highest
speed of photosynthesis changes from (plant) species to
species. According to Akman and Güney [19], usually
20-35ºC are optimum values for photosynthesis, and the
positive inuence of temperature on photosynthesis can
continue until 30ºC. This is consistent with the results
of the present study. Indeed, increasing temperature
raised the inuence of the plants on the CO2 amount,
and the inuence of the plants on the CO2 amount started
to decrease after 25ºC for Ficus, Dieffenbachia, and
Spathiphyllum, and after 20°C for Yucca. At 35°C, Ficus
showed a considerable inuence on the CO2 amount,
whereas Spathiphyllum and Yucca showed a limited
inuence. Meanwhile, Dieffenbachia started respiration
at 35ºC.
In the present study, all the plants photosynthesized
even at 15ºC. In general, the period of vegetation is
considered to cover the days when temperature is not
less than 10ºC [20]. Akman and Güney [19] reported that
some conifers continue to photosynthesize even at -30ºC
in temperate regions of the world.
Light is possibly the most important factor that
determines the inuence of plants on indoor CO2 amount.
Some studies have attempted to determine how plants
Species Temperature
15ºC 20ºC 25ºC 30ºC 35ºC
Ficus -42.08 -408.08 -480.74 -245.52 -216.68
Dieffenbachia -29.09 -273.10 -315.41 -80.88 4.86
Spathiphyllum -32.26 -220.92 -393.12 -123.78 -10.52
Yucca -6.28 -167.54 -93.74 -50.96 -22.42
Table 2. Inuences of the species on CO2 amount under 20,000
lux light depending on temperature.

1648 Sevik H., et al.
inuence the CO2 amount in controlled environments. Cetin
and Sevik [5] conducted a study regarding the reduction in
CO2 amount in an area of 0.5 m3. During the day, Ficus
elastica reduced CO2 by 2,216 ppm, Yucca massengena
by 2,578 ppm, Ocimum basilicum by 401 ppm, Sinningia
speciosa by 725 ppm, and Codia eumvariegatum by
790 ppm. During the night, on the other hand, Ficus
elastica increased the CO2 amount in the environment
by 351 ppm, Yucca massengena by 310 ppm, Ocimum
basilicum by 11 ppm, Sinningia speciosa by 218 ppm, and
Codiaeum variegatum by 84 ppm.
In another study, Sevik et al. [16] determined that
during the day Schefflera arboricola reduced the CO2
amount in a 0.5 m3 area by 1,252 ppm, whereas Fuchsia
magellanica reduced it by 252 ppm. Signicant differences
were observed between the plants in terms of the ratio of
the CO2 amount consumed through photosynthesis to the
CO2 amount produced through respiration (e.g., the ratio
being over 3.5 in Schefflera arboricola and less than 2 in
Fuchsia magellanica).
The results of the present study show that Yucca
is one of the plants that requires direct sunlight, and
Dieffenbachia and Spathiphyllum are ornamental plants
that seek half-shadow conditions [16]. In the research
conducted on Raphanussativus L. var. Saxa under high-
and low-light conditions, Lichtenthaler (1979) grew plants
in the dark
Ficus Dieffenbachia Spathiphyllum Yucca
Temperature
Leaf
Surface
(m2)
Average*
(reduction of
CO2 per hour)
Leaf
Surface
(m2)
Average*
(reduction of
CO2 per hour)
Leaf
Surface
(m2)
Average*
(reduction of
CO2 per hour)
Leaf
Surface
(m2)
Average*
(reduction of
CO2 per hour)
15ºC
0.185 7 0.192 0.7 0.336 12.4 0.1395 2.4
0.403 15.3 0.384 3.3 0.426 28.2 0.298 5.8
0.514 20.8 0.469 4.5 0.516 31.7 0.509 9
0.726 27.6 0.628 4.1 0.712 44 0.745 15.9
0.806 31.5 0.747 5.1 1.038 63.6 0.837 14
20ºC
0.185 8.4 0.192 2.7 0.336 24.3 0.1395 5.1
0.403 18.3 0.384 6.8 0.426 26.9 0.298 10.4
0.514 25.4 0.469 7.9 0.516 39.7 0.509 18.4
0.726 35 0.628 10.4 0.712 45.7 0.745 26
0.806 40.6 0.747 10.8 1.038 78.9 0.837 31
25ºC
0.185 6.2 0.192 1.8 0.336 54 0.1395 7.3
0.403 12.7 0.384 2.9 0.426 64.3 0.298 15.4
0.514 14.1 0.469 3.8 0.516 63.5 0.509 22.9
0.726 21.5 0.628 5.1 0.712 67.5 0.745 40.6
0.806 34.1 0.747 8 1.038 122.5 0.837 41.1
30ºC
0.185 11.1 0.192 2.9 0.336 22.3 0.1395 4
0.403 23.3 0.384 4.4 0.426 30.6 0.298 9.7
0.514 31.8 0.469 4.3 0.516 31.4 0.509 15
0.726 43.4 0.628 6.7 0.712 41.7 0.745 27.6
0.806 46.4 0.747 7.5 1.038 70.6 0.837 22.8
35ºC
0.185 18.7 0.192 2.1 0.1395 1.9
0.403 40.9 0.384 2.9 0.298 4.4
0.514 51.7 0.469 2.9 0.509 11.2
0.726 70.8 0.628 4.7 0.745 14
0.806 87.8 0.747 6 0.837 16.3
*Mean average is reduction of CO2 per hour
Table 3. Inuences of the species on CO2 amount in the dark depending on leaf surface and temperature.

1649
The Influence of House...
under 20,000-24,000 lux as a high-light condition. Studies
show that plants like Heliamphora and Sarracenia require
25,000 lux 12 to 16 hours a day [16].
Given this information, 20,000 lux was considered to
provide natural growth conditions for the plants. However,
light is a comprehensive issue, and quality, quantity, and
duration of light, besides its intensity, are important and
inuential in photosynthesis [21]. Hence, future research
should focus on these aspects separately in detail.
In the present study, all the plants increased their CO2
amounts in the dark. In other words, they respired in the
dark environment. This result is known and is mentioned
in many studies [19, 22-23].
Another important result involves the ratio of the CO2
amount exhaled to the environment through respiration
to the CO2 amount inhaled from the environment
through photosynthesis during the day. At the optimum
temperatures for the plants, the CO2 amount obtained
by the plants from the environment in the presence of
light was considerably higher than the CO2 amount they
emitted to the environment through respiration in the
dark. For example, at 25ºC, Dieffenbachia consumed
315.41 ppm CO2 in the light environment in one hour.
However, at the same temperature level it produced only
8.77 ppm CO2 in the dark environment. That is, the CO2
amount it consumed under 20,000 lux light conditions
in one hour was 36 times as much as the CO2 amount it
produced in the dark at the same temperature. Therefore,
plants can have a signicant positive effect on indoor CO2
amount in summer months when sunlight is received for a
long time and temperature is high.
The plants used in the study were selected from among
the most frequently used indoor plants. If research is
diversied and different factors are included, considerably
more effective and important results can be obtained in
this matter. For example, leaf structure must be included in
future research. Kacar et al. [15] reported that some plant
leaves are thick and enjoy the light less. When selecting
the intensity of light, the fact that optimum quantity
of light is different for every plant must be considered,
and plants of light and plants of shadow should not be
evaluated under the same light conditions. Indeed, Kacar
et al. [15] stated that the ratio of quantity of light needed
for the highest amount of photosynthesis is 8:1 for plants
of sun and plants of shadow. This shows how important
choice of light is for maximum photosynthesis speed.
Plants are living organisms. They need certain
conditions to survive. In addition, they change the
conditions of the environment they are in through
their metabolic activities. When the conditions in the
environment are suitable for plant development, they
emit oxygen to the environment and absorb CO2 from the
environment, but the opposite happens when conditions
change [10]. This condition inuences the CO2 amount
in the environment as well. A study on this subject
concluded that the CO2 amount in forestland averages
around 391 ppm during the daytime and around 422 ppm
during the nighttime in winter months, and around
148 ppm during the daytime and 229 ppm during the
nighttime in summer months [24].
Many studies have shown that indoor ornamental
plants can be used to reduce various indoor pollutants
[25-26]. Torpy et al. [27] explored the potentials
of Aglaonemacommutatum, Aspidistra elatior,
Castanospermumaustrale, Chamaedoreaelegans,
Dracaena deremensis compacta, Dypsislutescens, Ficus
benjamina, and Howeaforsterianato in reducing indoor
CO2 and found that the reducing effects of plants vary
depending on light conditions. Plants have a great variety
of reducing effects depending on light conditions. In
this study, the plants were rst kept in high- or low-light
conditions for 93 days, thereby accustoming them to the
relevant quantity of light. The CO2 amount that was reduced
under 10 µmol PAR m-2s-1 and 350 µmol PAR m-2s-1 light
conditions was then determined. Then how much they
reduced the CO2 amount under 10 µmol PAR m-2s-1 and
350 µmol PAR m-2s-1 light conditions was determined. The
highest values were obtained in D. lutescens, which had
been accustomed to high-light conditions before, under
350 µmol PAR m-2s-1. D. lutescens, having a leaf surface
of 1 m2, reduced the CO2 amount in the environment by
approximately 657 ppm in one hour. The second highest
value was obtained in D. deremensis (397 ppm) under the
same conditions.
The results of the present study indicate that plants can
considerably decrease the CO2 amount in the air, especially
in light environments. Although plants are especially used
for aesthetic and visual purposes, they affect the CO2
amount in the environment [2]. Previous research indicates
that a beech tree with a leaf surface of 1,600 m2 can satisfy
the oxygen need of 10 people [3-5, 16]. Torpy et al. [27]
compared eight species. In the end, they revealed that if
D. lutescens is used, which is the species having the
highest reducing effect on CO2, 249 plants should be
placed in an environment to balance the CO2 amount
produced by a human being. Torpy et al. [27] stated that if
H. forsteriana is used for the same purpose, 206 plants will
be needed since H. forsteriana has a wider leaf surface.
According to Pennisi and Iersel [28], approximately
400 plants will be needed if Spathiphyllum is used for the
same purpose.
Although these results indicate that indoor plants do
not have an adequate effect in reducing the CO2 amount
in practice, two points should be noted. First, plants not
only reduce indoor CO2 amount but also fulll many
Species Temperature
15ºC 20ºC 25ºC 30ºC 35ºC
Ficus 38.64 47.76 32.82 59.50 101.92
Dieffenbachia 7.04 15.93 8.77 11.29 8.04
Spathiphyllum 57.56 70.58 129.62 65.14 -
Yucca 18.16 35.62 50.08 30.70 17.38
Table 4. Inuences of the species on CO2 amount in the dark,
depending on temperature.

1650 Sevik H., et al.
other functions. Before anything else, plants reduce
many pollutants such as nitrogen and sulfur oxides,
carbon monoxide, volatile organic compounds, parti-
cles, ozone, NO2 (Nitrogen dioxide), formaldehydes,
and heavy metals [6, 29]. Furthermore, indoor plants
psychologically relieve people, reduce their stress and
other negative feelings, and improve their productivity [3,
7, 30].
Conclusions
The features sought in plants to be selected should be
determined based on environmental conditions to ensure
a more efcient use of plants. Research on this subject is
inadequate for now. More research should be carried out
on different plants; plants that photosynthesize faster in
indoor conditions should be investigated; and different
varieties, forms, and origins of the same species should be
included in analyses.
The results of this study show that plants help reduce
the CO2 amount in the light environment at different
levels. Among the species used, Ficus is the plant that
reduces the CO2 amount in the environment the fastest.
Therefore, Ficus is the most suitable species to be used in
reducing indoor CO2 amount, among the species included
in the study. However, only four species were used in
this study. If similar research is carried out on a variety
of species, crucial information should be obtained with
regard to which plants must be used to effectively reduce
the CO2 amount in the environment.
Environmental conditions considerably inuence
speeds of photosynthesis of plants and thus their
inuence on CO2. Therefore, inclusion of factors such as
temperature, light, plant size, and leaf structure in future
research is important for determining which plants are
more effective in specic environmental conditions.
Acknowledgements
This study is funded by the Scientic and Technological
Research Council of Turkey (TUBITAK) with project No.
114Y033. We all thank TUBITAK for its support.
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