TYPE Original Research

PUBLISHED 13 November 2023

DOI 10.3389/fbuil.2023.1286053

Assessing the impact of ventilation

OPEN ACCESS systems on indoor air quality: a
EDITED BY
Hasim Altan,
Prince Mohammad bin Fahd University,
mock-up experiment in Dubai
Saudi Arabia

REVIEWED BY Chuloh Jung 1, Gamal El Samanoudy 2*, Nahla Alqassimi 3 and

Nishant Raj Kapoor,
Academy of Scientific and Innovative
Mohammed Sherzad 3
Research (AcSIR), India 1
Department of Architectural Engineering, College of Engineering, University of Sharjah, Sharjah, United
Chanjuan Sun, Arab Emirates, 2Department of Interior Design, College of Architecture, Art, and Design, Ajman University,
University of Shanghai for Science and Ajman, United Arab Emirates, 3Department of Architecture, College of Architecture, Art, and Design,
Technology, China Ajman University, Ajman, United Arab Emirates
*CORRESPONDENCE
Gamal El Samanoudy,
g.elsamanoudy@ajman.ac.ae

RECEIVED 30 August 2023 Indoor Air Quality (IAQ) has become an important concern in Dubai, driven by public
ACCEPTED 23 October 2023
PUBLISHED 13 November 2023
health awareness, environmental regulations, and government initiatives. The Dubai
Municipality has introduced guidelines and standards for IAQ in residential and non-
CITATION
Jung C, El Samanoudy G, Alqassimi N and residential buildings, emphasizing ventilation, material selection, and testing
Sherzad M (2023), Assessing the impact of protocols. IAQ monitoring and testing are encouraged, and public awareness
ventilation systems on indoor air quality: a campaigns educate individuals about IAQ and its impact on health. Green building
mock-up experiment in Dubai.
Front. Built Environ. 9:1286053. regulations in Dubai also address IAQ considerations. The Dubai Municipality has
doi: 10.3389/fbuil.2023.1286053 comprehensively assessed IAQ in public buildings, leading to stringent regulations.
COPYRIGHT
However, research on IAQ improvement and challenges associated with apartment
© 2023 Jung, El Samanoudy, Alqassimi ventilation systems is limited. This study aims to evaluate the IAQ improvement and
and Sherzad. This is an open-access potential issues of a ventilation system in an apartment through a mock-up
article distributed under the terms of the
Creative Commons Attribution License experiment. Factors such as air volume, ventilation system type, and supply/
(CC BY). The use, distribution or exhaust duct configuration are analyzed. The results show that installing a
reproduction in other forums is ventilation device with a ventilation rate of 0.3–0.8 times/h reduces Formaldehyde
permitted, provided the original author(s)
and the copyright owner(s) are credited (HCHO) and Volatile Organic Compounds (VOCs) concentrations by 30%–50%. The
and that the original publication in this IAQ improvement is not significantly influenced by air volume. Each room supply/
journal is cited, in accordance with exhaust method shows a 10% higher reduction in VOC concentrations than the
accepted academic practice. No use,
distribution or reproduction is permitted supply/kitchen exhaust unit method. Preventing backflow and addressing cold drafts
which does not comply with these terms. are recommended during ventilation system installation. Noise measurements
comply with standards in most cases. These findings contribute to developing
guidelines for ventilation system design and installation in apartments, promoting
healthier indoor environments. Further research with a broader range of ventilation
devices and real-world conditions is recommended to validate these findings.

KEYWORDS

indoor air quality (IAQ), formaldehyde (HCHO), volatile organic compounds (VOCs),
ventilation systems, mock-up experiment

1 Introduction
The recognition and emphasis on Indoor Air Quality (IAQ) in Dubai have markedly
increased in recent years (Jung and Awad, 2021a; Awad and Jung, 2021; Awad and Jung,
2022). This uptick can be linked to various elements, such as growing public health
awareness, stringent environmental standards, and forward-thinking governmental
actions (Jung et al., 2021a; Awada et al., 2021; Jung and Al Qassimi, 2022). Heeding
these concerns, Dubai’s authorities have rolled out diverse strategies to mitigate air
contamination and bolster IAQ in indoor environments like homes, workplaces,

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educational institutions, and shopping centers (Mannan and Al-

Ghamdi, 2021; Kakoulli et al., 2022). A pivotal move in this endeavor
has been the Dubai Municipality’s launch of regulations and
directives, specifically the “Indoor Air Quality Standard DM 04
(2013)” for residential infrastructures and the “Indoor Air Quality
Standard DM 04 (2017)” for commercial properties (Jung and
Awad, 2021b; Mahmoud et al., 2023a). These all-encompassing
IAQ regulations address vital concerns such as ventilation,
material selection, and indoor testing methodologies (Arar and
Jung, 2021). Adherence to these standards is obligatory for
enterprises and property owners to guarantee a salubrious setting
for inhabitants (Jung et al., 2022a; Jung and El Samanoudy, 2023).
Beyond regulations, there’s a strong push for IAQ monitoring
and testing among organizations (Steinemann et al., 2017).
Consistent monitoring allows for early detection of IAQ
problems, leading to swift rectifications (Rickenbacker et al.,
2020; Monge-Barrio et al., 2022). The Environmental Department
of Dubai Municipality performs IAQ audits to confirm buildings
meet the established standards (Dubai Municipality, 2023b). Public
awareness drives are crucial in informing individuals about IAQ’s
importance and its ramifications on health (Marques et al., 2020;
Sadrizadeh et al., 2022). These drives include workshops, seminars,
and conferences on IAQ themes to enlighten the public (Jung et al.,
2022b; Jung et al., 2022c). Dubai has also adopted green building
standards like the “Al Safat Green Building Rating System” and the
“Dubai Green Building Regulations and Specifications.” These FIGURE 1
Research Process to evaluate the Effectiveness of Ventilation
prioritize sustainable construction and energy efficiency (Dubai System on IAQ.
Municipality, 2023a), specifically focusing on IAQ factors such as
proper ventilation, utilization of low-emission materials, and the
correct setup of air filtration systems (Arar et al., 2021; Jung et al.,
2022d). examining the effectiveness of IAQ improvement and the various
The Public Health and Safety Department of the Dubai challenges associated with installing ventilation systems in
Municipality has taken the initiative to comprehensively assess apartments (Jung and Arar, 2023). Moreover, reference materials
IAQ in public buildings, encompassing educational institutions, are scarce that guide constructing an efficient ventilation system (Al
universities, schools, nurseries, kindergartens, and healthcare Qassimi and Jung, 2022). While some luxury high-rise residential
centers (Jung et al., 2021b; Arar et al., 2022). This extensive buildings have adopted waste heat recovery ventilation systems,
evaluation has led to the establishment of stringent regulations complaints regarding cold drafts during winter have been reported
governing IAQ standards (Jung and Awad, 2023). As per these (Jung et al., 2021e; Kharrufa et al., 2022).
guidelines, the presence of formaldehyde (HCHO) should not The World Health Organization (WHO) advises an indoor
exceed 0.08 ppm, while the levels of Total Volatile Organic air concentration limit of 0.1 mg/m3 for formaldehyde (HCHO)
Compounds (TVOC) must not exceed 300 μg/m3 (Bani over 30 min to prevent sensory irritation in the majority of
Mfarrej et al., 2020). Furthermore, suspended particulate individuals. For Toluene, they recommend a weekly average of
matter measuring less than 10 microns in size (PM10) should not 260 μg/m3 to counteract annoyance and potential neurotoxic
exceed 150 μg/m3 during continuous monitoring over 8 h before effects (World Health Organization, 2010). Abdul-Wahab
occupancy (Mahmoud et al., 2023b; Gilbey et al., 2023). These et al. (2015) thoroughly review standards and guidelines
stipulations have been implemented to ensure optimal IAQ established by international entities, stressing the need for
conditions and promote a healthy and safe environment for stringent ventilation and air purification measures to diminish
occupants in public buildings (Jung et al., 2021c). Continuous pollutant levels and their subsequent health implications. Basner
efforts to improve building standards and enhance public et al. (2014) further underscore the importance of regulating
education will further contribute to the advancement of IAQ and indoor noise, especially during nighttime, for restorative sleep
the creation of a healthier living environment for the people of Dubai and overall wellbeing. These collective studies highlight the
(Jung et al., 2021d; Abdelaziz Mahmoud and Jung, 2023). significance of effective ventilation in achieving and upholding
As part of its efforts to enhance IAQ, the Dubai Municipality has optimal indoor air quality.
implemented regulations requiring the installation of either natural This research study aims to address these gaps by conducting a
ventilation facilities or mechanical ventilation systems capable of comprehensive mock-up test on a ventilation system installed in an
providing continuous ventilation for 24 h, with a minimum apartment, focusing on identifying the impact on IAQ improvement
ventilation rate of 0.7 times the room volume (Jung et al., 2022e; and evaluating potential issues. The mock-up experiment will assess
Sherzad and Jung, 2022). However, there is a lack of research the effectiveness of the ventilation system in improving indoor air

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TABLE 1 Overview of target units setting.

Category Compositions
Site Sobha creek vistas tower a in mohamed bin rashid city, Dubai

Unit type 2 bedroom apartment unit

Ventilator Type Unit Number Type ACH Ducttype

202 (NE_01) No heat exchanger N/A N/A

203 (TE_02) Total heat exchanger 0.3 Standard

302 (TE_03) Total heat exchanger 0.5 Standard

303 (TE_04) Total heat exchanger 0.8 Standard

502 (SE_05) Sensible heat exchanger 0.5 Standard

503 (TE_06) Total heat exchanger 0.5 Individual room

602 (AE_07) Alternating current type 0.5 Individual room

Temperature 24°C

Humidity Humidifier (No adjustment))

FIGURE 2
Sobha Creek Vistas Tower A in Mohamed Bin Rashid City. (A) façade/side view, and (B) interior of the unit (602 (AE_07).

quality, considering factors such as air volume, ventilation system 2 Materials and methods
type, and supply/exhaust duct configuration (Shin et al., 2018).
Additionally, parameters such as supply/exhaust temperatures and 2.1 Composition of target units
noise levels will be examined (Han, 2021). By analyzing the results of
this study, valuable insights can be gained into the IAQ Table 1 provides an overview of the mockup units used in this
enhancement potential and potential challenges associated with study. The mockup units consist of seven adjacent apartment units
ventilation system implementation in apartments (Awad et al., on the second to sixth floors of Sobha Creek Vistas Tower A in
2022) (Figure 1). These findings will contribute to developing Mohamed Bin Rashid City, Dubai (Figure 2) (Sobha Residence,
guidelines and best practices for designing and installing effective 2023). These units were finished with identical specifications
ventilation systems promoting healthier indoor environments in simultaneously (Jung et al., 2022f). One of the seven units serves
residential settings (Jung and Abdelaziz Mahmoud, 2023). as a blank household without a ventilation system installed (Zhang

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TABLE 2 Ventilator (in Blue) and Ductwork Setting showing Return Air RA (in Red).

Category Ventilator and Ductwork setting

Total heat exchanger and sensible heat exchanger (standard)

Total heat exchanger (Individual room)

Alternating current type

et al., 2020). This household serves as a benchmark for future Furthermore, to explore the differences based on duct methods,
comparative analysis. ducts were installed in the basic type and each room supply/exhaust
To investigate the impact of ventilation on improving indoor air type of the total heat exchange type ventilation device (ventilation
quality, the total heat exchange type ventilation system was set to frequency of 0.5 times/h) (Biler et al., 2018; Elsaid and Ahmed,
three stages: 0.3, 0.5, and 0.8 times/h (Zhao et al., 2020; Lee et al., 2021). After the mockup units were constructed, two units on the
2022). Additionally, three types of ventilation devices were used: third floor were chosen. The aim was to measure the infiltration rate
total heat exchange type, sensible heat exchange type, and AC type and assess its impact on IAQ. Specifically, we looked at
(Choi et al., 2018; Jung and Mahmoud, 2022). These devices were concentrations of pollutants (HCHO and Toluene) and thermal
installed based on a ventilation frequency of 0.5 times/h. conditions that could adversely influence the health, comfort, and

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performance of the building’s occupants (Palanisamy and Ayalur, TABLE 3 Measurement schedule.
2019).
Year Date On Off
The infiltration rate was measured using the constant
concentration method with SE_05 (Liang et al., 2022). The 2022 December 10 ○
measurement results indicated an infiltration rate of 0.75 times/h December 14 ○
for the NE_01 unit and 0.65 times/h for the TE_02 unit, representing a
December 17 ○
difference of 0.1 times/h. Although a 0.1 times/h difference in
infiltration rate is not negligible, it was considered an error factor December 21 ○
for subsequent IAQ measurements, and no specific measures were
December 24 ○
taken to address it (Ben-David and Waring, 2018; Alonso et al., 2022).
Following the infiltration measurement, the supply/exhaust 2023 January 2 ○
volume of the ventilation system was adjusted through TAB January 7 ○
(Testing, Adjusting, and Balancing), ensuring that the opening
January 15 ○
rate of the exhaust diffuser matched the set value for each
household and room (Degois et al., 2021). The apartment February 2 ○
interiors were maintained at a room temperature of 24°C using
February 5 ○
air conditioning, and a household humidifier was installed in the
living room for humidification (Zhao et al., 2018). During the February 10 ○
operation of the ventilation system, the indoor relative humidity February 18 ○
did not reach 50% with a single household humidifier (Okada et al.,
February 23 ○
2022). However, considering using one humidifier per unit is
common, only one humidifier was installed, and the
humidification amount was set to the maximum.
Table 2 provides an overview of the ventilation system - the blue outside air sampling was conducted on the balcony of the fifth-
lines show the ventilators and the red lines show the return air ducts floor living room side (Settimo et al., 2020).
- duct installation, and the state of duct insulation. For the total heat Table 3 outlines the sampling schedule based on the operating
exchange type (ventilation frequency of 0., 0., and 0.8 times/h) and conditions of the ventilation system. Under the “ventilator OFF”
sensible heat exchange type duct systems, air supply diffusers were condition, IAQ measurements were taken to assess the effectiveness of
installed near the windows of each room. In contrast, exhaust the ventilation system in reducing indoor air pollutant concentrations
diffusers were positioned near the dining room and entrance in (Földváry et al., 2017). This involved following the IAQ Management
the upper part of the corridor (Zhong et al., 2020; Al-Rawi et al., Act recommended by the WHO, where the ventilation system is
2022). This configuration, named the basic type, was adopted in this continuously operated at the construction site but stopped during
study (Ghani et al., 2018). In contrast, each room supply/exhaust indoor air sampling (World Health Organization, 2010).
duct system involved the installation of an air supply diffuser and an In contrast, under the “Ventilation device ON” condition, the
exhaust diffuser in each room (Soares et al., 2021). The air supply ventilation system was operational during indoor air sampling to
diffuser was located similarly to the basic type, while the exhaust assess the IAQ improvement effect achieved by operating the
diffuser was positioned near the door of each room (Bai et al., 2022). ventilation device (Yin et al., 2019; Kozielska et al., 2020).
In the AC-type system, exhaust and supply air alternated through a Additionally, temperature/humidity data logger sensors were
single duct, with a diffuser installed near the window of each room installed in the supply air (SA) and return air (RA) ducts near
(Kwok et al., 2022; Tan et al., 2023). The AC ventilation system was the ventilation system (Ismaeel and Mohamed, 2022). These sensors
designed to perform one cycle every 6 min, with exhaust for 3 min recorded the temperature/humidity of the supply/exhaust air at 10-
followed by air supply for 3 min (Xue et al., 2020). While the ducts min intervals (Da Silva et al., 2017). The measurement of noise levels
inside the units were not insulated, the outdoor duct sections were by the Dubai Municipality Noise Vibration Process Test Method
insulated (Ismail et al., 2023). was conducted while considering the operation of the ventilation
system (Lei et al., 2019). The living room and main room, which
featured supply/exhaust diffusers, were selected as representative
2.2 Measurement method rooms for measurement (Cho et al., 2019). Five points, including the
center of each room, were measured to determine the noise levels
The research study measured indoor air quality (IAQ), (Sarkhosh et al., 2021). To account for background noise, the
specifically Formaldehyde and Toluene, supply/exhaust measured noise level values in each room were adjusted using
temperature, and noise levels of the ventilation system operation the background noise value from the household without a
(Szabados et al., 2021). The IAQ concentration measurement ventilation system.
followed the IAQ Process Test Method outlined by the World
Health Organization (WHO) for sampling and analysis (World
Health Organization, 2010). The measurement period spanned 2.3 Measurement tools and scenario
2 months, from 10 December 2022, to 23 February 2023, with
12 indoor air sampling and analysis sessions. Sampling within The measured indoor air pollutants were formaldehyde
the unit took place in the center of the living room, while (HCHO) and Toluene. The measurement method is based on the

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TABLE 4 Measuring IAQ factors and scenario.

Measuring factors Measurement Measuring time Measuring location

Background Indoor Digital Thermo-Hygrometer 10:00 a.m.–6:00 p.m. (Autosave every 1.5 m from the floor in the center of the living
Factors Temperature (TR-72U) 10 min for 8 h) room

Relative Humidity

IAQ Factors Formaldehyde DNPH Cartridge Σ300 Pump 10:00 a.m.–6:00 p.m. (Measured every
20 min)

Toluene Tenax Tube Σ300 Pump 10:00 a.m.–6:00 p.m. (Measured every
20 min)

FIGURE 3
HCHO concentration change (ventilator off).

WHO standards, measured 1.5 m from the living room center from 3 Results
10 a.m. to 6 p.m. (Table 4) (World Health Organization, 2010). For
the first step to measure formaldehyde (HCHO) concentration, all The room temperature was kept constant throughout the
windows and interior furniture doors are opened for 30 min to measurement at the set temperature of 24°C. However, the humidity
perform natural ventilation before sampling. As the second step, varied among households due to the differences in ventilation rates.
close all the windows for more than 5 h to prevent airflow (Yin et al., Figure 3 and Figure 4 depict the changes in HCHO concentration
2019). The furniture, doors, and built-in cabinet are opened to allow during the measurement period for the ‘ventilator OFF’ and “ventilator
air movement for indoor air pollutant collection. In the third step, a ON” conditions, respectively. In both cases, the HCHO concentration
sample is collected with a DNPH (2,4-Dinitrophenylhydrazine) generally satisfies the IAQ recommendation standard of 210 μg/m3.
cartridge after 5 h, rolled up with tinfoil to block any possible However, the concentration does not decrease over time and shows a
light effects (Kozielska et al., 2020). At this time, the natural and slight upward trend. This can be attributed to the gradual emission of
forced ventilation is sealed, and samples are collected. An ozone HCHO from the complex composition of finishing materials, which
scrubber is used to collect air samples, and 15 L is collected for gradually increases over time.
20 min using a precise mini suction pump (0.5 mL/min). The air Regarding VOCs, toluene exhibits the highest concentration, and the
samples in the last step are precisely analyzed by HPLC (High- trend of other VOC substances in terms of reduction over time is similar
Performance Liquid Chromatography). In the TVOC concentration to that of toluene. Therefore, this paper focuses on analyzing the changes
measurement method, the two stages of the formaldehyde (HCHO) in toluene concentration. Figure 5 and Figure 6 illustrate the variations in
sampling method are the same, and a Tenax tube is used in the third toluene concentration for the “ventilator OFF” and “ventilator ON”
step (Ismaeel and Mohamed, 2022). The last step analyzes the air conditions, respectively. Under the “ventilator ON” condition, the toluene
sample by GC/MS (Gas Chromatography/Mass Spectroscopy). concentration experienced a significant increase on December 21st,
However, since the device used in this study is a direct-reading followed by a rapid decrease on January 7th, approximately 1 month
method for instantaneous values, it measures instantaneous into the measurement period, ultimately falling below the standard value.
concentrations multiple times, unlike the collection method of Subsequently, the rate of decline slowed down. On the other hand, for the
process test methods (Da Silva et al., 2017). “ventilator ON” condition, the concentration of toluene reached its

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FIGURE 4
HCHO concentration change (ventilator on).

FIGURE 5
Toluene concentration change (ventilator off).

highest value on December 21st and gradually decreased over time. By To address this issue, the concentration values for each
January 15th, around 1 month after the start of measurement, the measurement day were dimensionless concerning the
concentration consistently satisfied the standard value. concentration on December 10, the first day of measurement.
These values were then presented as a percentage multiplied by
100 for comparison and review. Figure 7 and Figure 8 illustrate the
3.1 IAQ improvement according to dimensionless concentration of HCHO at different air volumes of
ventilation amount change the ventilator, corresponding to ventilation frequencies of 0.3, 0.5,
and 0.8 times/h. Figure 7 depicts the case of “ventilator OFF,” it
To compare and analyze the temporal change in pollutant shows no significant difference in HCHO concentration over time
concentration, it is crucial to account for different temperature/ between households with and without a ventilation system initially.
humidity conditions during measurement. Therefore, in this study, However, after 1.5 months into the measurement period, specifically
the temperature and humidity conditions were standardized to 24°C on February 2, the formaldehyde and toluene improved by
and 50% using the Inoue equation. Moreover, since the initial approximately 20%. By the end of the 2-month measurement
concentration varies among generations, it is challenging to directly period on February 10, the improvement reached around 30%.
compare the formaldehyde and toluene improvement effect between This indicates the formaldehyde and toluene improvement effect
generations or the reduction effect in concentration over time. resulting from the regular operation of the ventilation system.

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FIGURE 6
Toluene concentration change (ventilator on).

FIGURE 7
HCHO concentration change by ventilation rate (ventilator off).

Regarding the formaldehyde and toluene improvement effect based humidity correction. Figure 9 and Figure 10 present the relatively
on ventilation rate variations, the concentration of HCHO was lower at dimensionless concentration of toluene for the “ventilator OFF” and
a ventilation rate of 0.3 times/h compared to 0.5 or 0.8 times/h. “ventilator ON” conditions, respectively. The toluene concentration
However, the difference was around 5%, within the measurement remained relatively high until December 24, 0.5 months into the
error range. Consequently, the effect of improving indoor air quality measurement period. During this period, with the ventilation system
based on ventilation variations did not demonstrate a significant turned OFF, there was an approximate 15% IAQ improvement effect
difference. In the case of “ventilator ON,” the average improvement compared to households without a ventilation system. This
effect was approximately 40%, except for January 15. However, the improvement can be attributed to the constant operation of the
difference associated with changes in air volume was approximately 5%, ventilation system. However, starting from January 7, approximately
which was considered within the measurement error range. These 1 month into the measurement period, the declining trend slowed
findings suggest that during the winter season in Dubai, which down, and the formaldehyde and toluene improvement effect due to
coincided with the measurement period, the infiltration rate was regular ventilation system operation became less apparent.
relatively high at approximately 0.7 times/h. As a result, the When comparing the differences based on air volume, the case of
difference in ventilation rate between 0.3 and 0.8 times/h was 0.3 times/h showed a lower value by approximately 5%. However,
relatively small, compounded by construction errors. considering the measurement error, this difference is considered
The toluene concentration was dimensionless concerning the insignificant. In the case of “ventilator ON,” the analysis focused only
concentration on the first measurement day without temperature/ on the measured values from December 21, January 15, and February 23,

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FIGURE 8
HCHO concentration change by ventilation rate (ventilator on).

FIGURE 9
Toluene concentration change by ventilation rate (ventilator off).

excluding instances where the outdoor air concentration was affected by exchanger types, namely, total heat exchange, sensible heat
road pavement work near the site during the measurement period. On exchange, and alternating current types, was examined. All three
December 21, when the concentration was at its highest, toluene ventilation systems operated at the same frequency of 0.5 times/h.
concentration in households without ventilation increased to about Figure 11 and Figure 12 present the relatively dimensionless
500% of the initial concentration. In households with ventilation, it concentration of HCHO according to the ventilation system type.
rose to approximately 300% regardless of air volume, resulting in a 40% In the case of “ventilator OFF,” the reduction effect in concentration
IAQ improvement effect. However, starting from January 15, is only apparent on January 7, approximately 1 month after the
approximately 1 month into the measurement period, the initial measurement. However, a reduction effect of around 15%
formaldehyde and toluene improvement effect due to the operation becomes evident from February 2, about 1.5 months into the
of the ventilation system gradually diminished. measurement period. By the end of the 2 months on February
10, the alternating current type demonstrated a 40% IAQ
improvement effect, while the sensible heat exchange type and
3.2 IAQ improvement according to the type total heat exchange type showed an improvement of
of ventilation system approximately 25%. When the ventilation system is “ON,” the
sensible heat exchange type exhibits a 50% improvement, while
The IAQ (formaldehyde and toluene) improvement effect of the total heat exchange type and AC type show a 40% improvement
waste heat recovery ventilation systems with different heat compared to units without ventilation, except for January 15.

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FIGURE 10
Toluene concentration change by ventilation rate (ventilator on).

FIGURE 11
HCHO concentration change by heat exchanger type (ventilator off).

Figure 13 and Figure 14 illustrate the relatively dimensionless initial concentration. At the same time, the sensible heat exchange
concentration of toluene for different waste heat recovery type reached 250%, and the total heat exchange type and AC type
ventilators. In the case of “ventilator OFF,” the total heat reached 300% and 350%, respectively. This resulted in a
exchange type and AC type show about a 10% improvement on formaldehyde and toluene improvement effect of approximately
December 17 and December 24, when the toluene concentration is 50% for the sensible heat exchange type and around 40% for both
relatively high compared to units without ventilation. On the other the total and AC types.
hand, the sensible heat exchange type demonstrates a relatively
higher formaldehyde and toluene improvement effect compared to
other ventilation device types. However, starting from January 7, 3.3 IAQ improvement according to the
when the concentration began to decrease, the differences supply/exhaust duct types
gradually diminished, and the formaldehyde and toluene
improvement effect became less evident. In the case of The ventilation system’s duct method is analyzed, comparing the
“ventilator ON,” excluding instances where the outdoor air IAQ (formaldehyde and toluene) improvement effect between each
concentration of toluene was high, the measured values on room supply/kitchen exhaust unit and each room supply/exhaust unit.
December 21, January 15, and February 23 were reviewed. The In the “ventilator OFF” scenario, formaldehyde concentration
concentration in units without ventilation was higher than the measurements were conducted until February 2nd, 1.5 months into

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FIGURE 12
HCHO concentration change by heat exchanger type (ventilator on).

FIGURE 13
Toluene concentration change by heat exchanger type (ventilator off).

the measurement period. Although the concentration reduction effect start of the measurement. Meanwhile, each room supply/kitchen
was not initially apparent, a slight reduction effect became noticeable on exhaust unit exhibited an improvement effect of about 10%. In the
February 2nd. After 2 months, on February 10th, each room supply/ ‘Ventilation ON’ case, when examining the data for December 26th,
kitchen exhaust unit and each room supply/exhaust unit exhibited an where the outdoor air concentration was relatively low, each room
improvement effect of 25% compared to units without ventilation. The supply/exhaust unit displayed a 50% improvement effect, while each
difference between the supply/exhaust duct methods was insignificant, room supply/kitchen exhaust unit showed a 40% improvement effect.
within 5%. In the “Ventilation ON” case, except for January 15th, each However, the 10% difference in the IAQ (formaldehyde and toluene)
room supply/kitchen exhaust unit showed a 40% improvement effect, improvement effect based on the supply/exhaust duct method is
while each room supply/exhaust unit demonstrated a 30% improvement considered insignificant when considering measurement errors.
effect compared to units without ventilation. The difference between the
two methods was within 10%. However, considering the margin of error,
there needs to be a clear distinction in the reduction effect of 3.4 Noise measurement result
formaldehyde concentration based on the supply/exhaust duct method.
The dimensionless concentration change of toluene is as follows. Table 5 presents the results of the noise measurements. When
In the “ventilator OFF” scenario, each room supply/exhaust unit considering the Dubai Municipality Building Code’s standard of
showed an improvement effect of approximately 25% compared to 40 dB(A), the noise levels in the living room range from 32.5 to
units without ventilation until December 24th, 0.5 months after the 41.8 dB(A), depending on the type of ventilation system. However,

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FIGURE 14
Toluene concentration change by heat exchanger type (ventilator on).

TABLE 5 Noise level.

Unit number Type ACH Living room (dB(A)) Bedroom (dB(A))

203 (TE_02) Total heat exchanger 0.3 35.2 31.8

302 (TE_03) Total heat exchanger 0.5 35.1 31.2

303 (TE_04) Total heat exchanger 0.8 32.5 28.2

502 (SE_05) Sensible heat exchanger 0.5 41.8 38.8

503 (TE_06) Total heat exchanger 0.5 38.2 30.7

602 (AE_07) Alternating current type 0.5 34.4 34.2

Background Noise 18.6 20.1

one unit registered a noise level of 41.8 dB(A), exceeding the standard. unexpected spike necessitates further exploration to understand its
On the other hand, all other units met the prescribed criterion. cause. However, some concentration reduction was observed even with
Regarding the master bedroom, the distribution of noise levels varies the ventilation systems turned OFF. Changes in the ventilation rate did
from 28.2 to 38.8 dB(A), depending on the type of ventilation system. not substantially impact IAQ improvement. Similarly, the type of heat
Notably, all measurements in this area adhered to the standard value. exchanger employed did not show significant differences in IAQ
improvement. Likewise, the supply/exhaust duct method choice did
not yield significant variations in IAQ improvement. However, it is
4 Discussion worth noting that noise levels in some units exceeded the noise level
standard specified by the Dubai Municipality Building Code.
The present study investigated the impact of different ventilation The implications of the study findings underscore the importance of
systems on IAQ and pollutant concentrations in an apartment setting. proper ventilation systems in enhancing formaldehyde and toluene by
Specifically, the focus was on HCHO and toluene concentrations. reducing formaldehyde and toluene concentrations. Adequate operation
Measurements were conducted under varying ventilation conditions, of ventilation systems is vital for maintaining a healthy indoor
including ventilator OFF and ventilator ON scenarios. The study also environment. While the specific variables examined in this study did
examined the influence of ventilation rate, heat exchanger type, and not significantly impact formaldehyde and toluene improvement, further
supply/exhaust duct method on IAQ improvement. Additionally, investigations can explore other factors that may influence formaldehyde
noise levels in the living room and master bedroom were assessed. and toluene. Moreover, adherence to noise level standards is crucial to
Interpretations of the findings indicate that the implemented ensure a comfortable living environment for occupants.
ventilation systems significantly improved formaldehyde and toluene
by reducing formaldehyde and toluene concentrations. The
formaldehyde and toluene improvement effects were more 4.1 Study limitations
pronounced when the ventilation systems were turned ON.
Intriguingly, on December 21st, there was a sudden surge in the Our study, centered within an apartment milieu, endeavored to
concentration of toluene despite the ventilator being ON. This discern the effects of diverse ventilation systems on IAQ,

Frontiers in Built Environment 12 frontiersin.org

Jung et al. 10.3389/fbuil.2023.1286053

predominantly focusing on the concentrations of HCHO importance of considering the specific duct configuration in
(formaldehyde) and toluene. We incorporated many ventilation achieving effective pollutant reduction.
conditions into our experimental design, encompassing scenarios Based on the study findings, it is recommended to include a duct
where ventilators were activated and deactivated (Al-Rawi et al., mechanism to prevent backflow during strong winds when
2022). Beyond these primary conditions, our research also delved implementing ventilation systems. Additionally, measures should
into the subtleties of ventilation rate, the intricacies of heat exchanger be taken to address potential issues of cold drafts to ensure occupant
types, and variations in the supply/exhaust duct methods, seeking comfort and satisfaction.
correlations with improvements in IAQ (Ghani et al., 2018). The noise measurements conducted during the study indicated
Our analysis shows that the ventilation systems employed had a that most of the recorded values complied with the standard of
tangible, positive influence on the IAQ by significantly reducing the 40 dB(A) or below. This reinforces the significance of considering
concentrations of formaldehyde and toluene. Interestingly, this noise control measures in ventilation system design and installation
enhancement in air quality was not solely contingent on the active to create a comfortable indoor environment.
ventilators. Even in their deactivated state, a reduction in pollutant While the results provide valuable insights, it is crucial to
concentration was discernible, albeit less pronounced than in the interpret them within the context of the specific mock-up
active state. Despite our thorough exploration of various parameters, experiment conducted. Further research and field studies
changes in ventilation rates, the type of heat exchanger, or the chosen involving a broader range of ventilation devices and real-world
supply/exhaust method did not appear to be critical differentiators in conditions are recommended to validate and generalize these
the level of IAQ improvement achieved (Bai et al., 2022). Nonetheless, findings. This will enhance our understanding of IAQ
one area of potential concern emerged from our findings: certain units improvement strategies and their applicability in various settings.
manifested noise levels that surpassed the prescribed thresholds set
forth by the Dubai Municipality Building Code.
Drawing from these insights, the overarching message is Data availability statement
unequivocal: proficient ventilation systems’ integration and
optimal operation are paramount for curtailing formaldehyde The raw data supporting the conclusion of this article will be
and toluene concentrations, fostering a salubrious indoor made available by the authors, without undue reservation.
ambiance. Although the variables examined in this iteration of
our research did not dramatically alter the levels of formaldehyde
and toluene, we acknowledge the vastness of the IAQ domain and Author contributions
anticipate that supplementary studies might unearth additional
influential factors. Ensuring adherence to noise regulations, as CJ: Conceptualization, Data curation, Formal Analysis,
evidenced by our findings, remains pivotal to providing residents Methodology, Resources, Validation, Visualization,
with a serene and healthful living environment. Writing–original draft. GE: Data curation, Investigation,
Methodology, Project administration, Software, Supervision,
Writing–review and editing. NA: Investigation, Project
5 Conclusion administration, Supervision, Validation, Visualization,
Writing–review and editing. MS: Methodology, Resources,
The mock-up experiment conducted in Sobha Creek Vistas Software, Validation, Visualization, Writing–review and editing.
Tower A provided valuable insights into the IAQ improvement
effect of mechanical ventilation systems. It is important to note that
the findings are specific to the ventilation devices used in this Funding
experiment and may not be universally applicable to all
ventilation systems. The results demonstrated that installing and The authors would like to thank Ajman University for financial
operating a ventilation device with a ventilation rate ranging from support.
0.3 to 0.8 times/h in the target units significantly reduced HCHO
and VOC concentrations. The IAQ improvement effect ranged from
30% to 50% compared to units without ventilation. This emphasizes Acknowledgments
the importance of implementing proper ventilation systems to
mitigate indoor air pollutants effectively. The authors would like to thank the University of Sharjah, and
Interestingly, the study revealed that the IAQ improvement the Sustainable Architecture and Resilient Design Research Group
effect was not directly influenced by the air volume of the (SARD-RG) for providing a great research environment, and Ajman
ventilation system within the tested range of ventilation University for financial support.
frequencies. Further investigation is required to explore other
factors that may contribute to IAQ improvements and determine
optimal ventilation parameters. Conflict of interest
Regarding the supply/exhaust duct method, it was observed that
each room supply/exhaust method demonstrated approximately a The authors declare that the research was conducted in the
10% higher reduction in VOC concentrations compared to each absence of any commercial or financial relationships that could be
room supply/kitchen exhaust unit method. This finding suggests the construed as a potential conflict of interest.

Frontiers in Built Environment 13 frontiersin.org

Jung et al. 10.3389/fbuil.2023.1286053

Publisher’s note organizations, or those of the publisher, the editors and the
reviewers. Any product that may be evaluated in this article, or
All claims expressed in this article are solely those of the authors claim that may be made by its manufacturer, is not guaranteed or
and do not necessarily represent those of their affiliated endorsed by the publisher.

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