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New Challenges for Indoor Air Quality

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Environmental Sciences".

Deadline for manuscript submissions: closed (20 December 2021) | Viewed by 30649

Special Issue Editor


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Guest Editor
Atmospheric Chemistry & Innovative Technologies Laboratory, Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, National Centre for Scientific Research “Demokritos”, 15310 Agia Paraskevi, Greece
Interests: indoor air quality; air pollution; source apportionment; particulate matter physics and chemistry; ventilation; exposure
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Unsurprisingly, during the last decades, indoor air quality (IAQ) has received increasing attention from the scientific community because of its evidenced impact on human health and comfort. Although extensive studies have revealed the major factors that affect the air quality inside buildings, there are still several challenging research questions to be answered:

  • Indoor Air Quality and viruses transmission: what do we need to know?
  • What are the advantages and limitations of air monitoring sensor networks for estimating IAQ?
  • IAQ, Internet of Things, and machine learning: how can we methodically explore and leverage the opportunity that lies in this triptych? Are there any existing paradigms that can be used to confront this, or does the scientific community need to build a new framework that will allow coordinated exploration of this new frontier?
  • Indoor Air Chemistry: Are the chemical transformations, aging, and formation of secondary pollutants in indoor air adequately studied? Which are the key gas and particle-phase species that determine IAQ? How important are the short-lived, highly reactive species?
  • Indoor air pollutants real-time monitoring and source apportionment: How feasible is it?
  • What are the advances of zero/low emitting and photocatalytic materials for IAQ?
  • How can a holistic understanding of the characteristics of sources, their interactions and pathways of human exposure be achieved?
  • What will be the future of IAQ in relation to climate change and energy conservation?

With this Special Issue (which comprises the second volume of the successful ‘Indoor Air Quality’ Special Issue in Applied Sciences), manuscripts addressing challenging future research for Indoor Air Quality are invited.

Dr. Dikaia E. Saraga
Guest Editor

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Keywords

  • Indoor air pollution
  • Air quality sensors
  • Internet of Things
  • Smart home
  • Indoor air monitoring
  • Indoor modeling
  • Occupant exposure
  • Viruses transmission
  • COVID-19

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Published Papers (10 papers)

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22 pages, 471 KiB  
Article
Privacy-Aware and Secure Decentralized Air Quality Monitoring
by Michael Mrissa, Aleksandar Tošić, Niki Hrovatin, Sidra Aslam, Balázs Dávid, László Hajdu, Miklós Krész, Andrej Brodnik and Branko Kavšek
Appl. Sci. 2022, 12(4), 2147; https://doi.org/10.3390/app12042147 - 18 Feb 2022
Cited by 6 | Viewed by 2989
Abstract
Indoor Air Quality monitoring is a major asset to improving quality of life and building management. Today, the evolution of embedded technologies allows the implementation of such monitoring on the edge of the network. However, several concerns need to be addressed related to [...] Read more.
Indoor Air Quality monitoring is a major asset to improving quality of life and building management. Today, the evolution of embedded technologies allows the implementation of such monitoring on the edge of the network. However, several concerns need to be addressed related to data security and privacy, routing and sink placement optimization, protection from external monitoring, and distributed data mining. In this paper, we describe an integrated framework that features distributed storage, blockchain-based Role-based Access Control, onion routing, routing and sink placement optimization, and distributed data mining to answer these concerns. We describe the organization of our contribution and show its relevance with simulations and experiments over a set of use cases. Full article
(This article belongs to the Special Issue New Challenges for Indoor Air Quality)
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Figure 1
<p>A layered system architecture.</p>
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<p>Incremental learning with Hoeffding trees.</p>
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<p>The figure shows the onion message traveling through the network and updating the DM model at sensor nodes in the message path. The onion head and onion body color change at each message processing to indicate the encryption operation.</p>
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<p>A plot of average ORTT of onion messages traveling through <math display="inline"><semantics> <mrow> <mi>n</mi> <mo>=</mo> <mfenced separators="" open="{" close="}"> <mn>5</mn> <mo>,</mo> <mn>20</mn> <mo>,</mo> <mn>60</mn> </mfenced> </mrow> </semantics></math> nodes and having onion body size of <span class="html-italic">p</span> = {1 k, 2.5 k, 5 k, 10 k, 25 k, 50 k, 100 k} bytes. The average was computed on 30 onion messages.</p>
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<p>Overview of overall time needed for read and write operations on different numbers of sensors.</p>
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10 pages, 663 KiB  
Article
Work Category Affects the Exposure to Allergens and Endotoxins in an Animal Facility Laboratory in Italy: A Personal Air Monitoring Study
by Simona Di Renzi, Alessandra Chiominto, Anna Maria Marcelloni, Paola Melis, Maria Cristina Riviello, Annarita Wirz, Renata Sisto, Stefania Massari, Emilia Paba and Maria Concetta D’Ovidio
Appl. Sci. 2021, 11(16), 7220; https://doi.org/10.3390/app11167220 - 5 Aug 2021
Cited by 1 | Viewed by 1986
Abstract
Scientists and technicians who work in contact with laboratory animals are exposed to complex biological mixtures from animals, bedding and feed. The main objective of this study was to characterize the exposures to endotoxins and animal allergens in a biomedical research institution located [...] Read more.
Scientists and technicians who work in contact with laboratory animals are exposed to complex biological mixtures from animals, bedding and feed. The main objective of this study was to characterize the exposures to endotoxins and animal allergens in a biomedical research institution located in Central Italy by means of air sampling in the breathing zone of the staff during daily work activities. Forty-two inhalable dust samples were collected for endotoxins and allergens analysis. Filter extracts were analyzed using a Kinetic-QCL LAL kit for endotoxins; ELISA assays were performed for Mus m 1, Rat n 1, Can f 1, Fel d 1 and Equ c 4 detection. Laboratory animal attendants (LAAs) showed endotoxin concentrations significantly higher (4.59 ng/m3) than researchers (0.57 ng/m3), researchers working only in an office (0.56 ng/m3) and technicians (0.37 ng/m3). Endotoxin concentrations exceeding the recommended occupational exposure limit proposed by the Dutch Expert Committee on Occupational Safety were found in the case of two subjects in the animal attendants category. With regards to rat and mouse allergens, a higher average dose was found for mouse than rat allergens. Also for these bio-contaminants, the LAAs are confirmed as the work category at higher risk of exposure (15.85 ng/m3), followed by technicians (10.67 ng/m3), researchers (2.73 ng/m3) and researchers in an office (0.08 ng/m3). Fel d 1 was also detected (average: 0.11 ng/m3) highlighting a passive transport between living and occupational settings. Our data could be useful to improve the control and preventive measures, ensuring lower levels of allergens and endotoxins in animal facilities. Full article
(This article belongs to the Special Issue New Challenges for Indoor Air Quality)
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<p>Work record sheet utilized to collected information on enrolled workers.</p>
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<p>Average concentration of bio-contaminants distributed in the four work categories under investigation.</p>
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33 pages, 6428 KiB  
Article
The Ability to Control VOC Emissions from Multilayer Building Materials
by Michał Piasecki, Krystyna Barbara Kostyrko and Anna Goljan
Appl. Sci. 2021, 11(11), 4806; https://doi.org/10.3390/app11114806 - 24 May 2021
Cited by 3 | Viewed by 3075
Abstract
The work aimed to investigate which parameters of the electrically powered radiant floor heating system are connected with the intensity of VOC total emissions and emissions from individual layers, which can be effectively changed and controlled to obtain energy savings in the ventilation [...] Read more.
The work aimed to investigate which parameters of the electrically powered radiant floor heating system are connected with the intensity of VOC total emissions and emissions from individual layers, which can be effectively changed and controlled to obtain energy savings in the ventilation process. For this purpose, experimental studies of VOC emissions from specially designed LRFHS samples (Laboratory Radiant Floor Heating System) were carried out, along with simulations of real thermal conditions of samples of layered systems containing separate heaters and various materials layers. The TD-GC-MS chromatography was used to assess the trends of VOCs concentration changes in 480 h in a test chamber (simulating real conditions) for several LRFHS systems of multilayer construction products with built-in individual heating systems, in two stabilised temperatures, 23 °C and 33 °C, two stabilised relative humidities, 50% and 80% and three air exchanges per hour ACH on levels 0.5, 1.0 and 1.5. The obtained results indicate that the models used to determine emissions from single-layer products correspond to the description of emissions from multilayer systems only to a limited extent; some inner layers of floor systems are giving diffusion resistance or intensification of diffusion. A new emission model is proposed. The time-emission concentration curves for dry and wet environments differ significantly; reducing the VOC concentration in the air for the number of exchanges above 1.0 ACH is relatively inefficient. Authors also mapped out new research directions; for example, the experiment showed that not all of the VOC contaminants are ventilated just as easily and perhaps, considering their concentration of resistant impurities, chemical structure and diffusion resistance through the layers, there is a need to determine their weights. Full article
(This article belongs to the Special Issue New Challenges for Indoor Air Quality)
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Figure 1
<p>Installation scheme for electrically powered radiant floor heating multilayers system.</p>
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<p>The housing of a heated floor sample type D (dry rooms).</p>
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<p>Cross-section of the heated floor sample (<b>a</b>) type D (<b>b</b>) type W (wet rooms).</p>
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<p>Picture of a cross-section of the sample type D (dry indoor conditions).</p>
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<p>Picture of a cross-section of the sample type W (wet indoor conditions).</p>
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<p>Test stand scheme (<b>a</b>): electrically powered radiant floor heating multilayers system (<b>b</b>) located in a test chamber; the control panel –conditioning parameters’ monitoring (<b>c</b>).</p>
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<p>Stability of temperature for the top layer T1, inside layer T2 and heater T3 in time for dry D-type samples (<b>a</b>) and wet W-type sample (<b>b</b>).</p>
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<p>The TVOC emission profiles from W3 sandwich floor systems (testedfor480 h) for three air changes rates (<span class="html-italic">n</span> = 0.5 h<sup>−1</sup>, 1 h<sup>−1</sup> and 1.5 h<sup>−1</sup>) at 23 °C and RH = 80% in the emission test chamber. (W3 sample is system is made of: polyurethane solvent primer, polymer–cement waterproofing and epoxy adhesive (see <a href="#applsci-11-04806-t003" class="html-table">Table 3</a>); significant VOCs compounds for these products are provided in <a href="#applsci-11-04806-t001" class="html-table">Table 1</a>).</p>
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<p>The TVOC emission profiles from W3 sandwich floor systems (test by 480 h) for three air changes rates (<span class="html-italic">n</span> = 0.5 h<sup>−1</sup>, 1 h<sup>−1</sup> and 1.5 h<sup>−1</sup>) at 33 °C and RH=80% in the emission test chamber. (W3 sample is a system made of: polyurethane solvent primer, polymer–cement waterproofing and epoxy adhesive (see <a href="#applsci-11-04806-t003" class="html-table">Table 3</a>); significant VOCs compounds for these products are provided in <a href="#applsci-11-04806-t001" class="html-table">Table 1</a>).</p>
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<p>The TVOC emission profiles from D1 sandwich floor systems (testedfor 480 h) for three air changes rates (<span class="html-italic">n</span> = 0.5 h<sup>−1</sup>, 1 h<sup>−1</sup> and 1.5 h<sup>−1</sup>) at 29 °C and RH = 50% in the emission test chamber. (D1 sample is a floor system made of: polyurethane solvent primer and polyurethane adhesive (see <a href="#applsci-11-04806-t003" class="html-table">Table 3</a>); significant VOCs compounds for these products are provided in <a href="#applsci-11-04806-t001" class="html-table">Table 1</a>).</p>
Full article ">Figure 11
<p>The TVOC emission profiles from D1 sandwich floor systems (tested for 480 h) for three air changes rates (<span class="html-italic">n</span> = 0.5 h<sup>−1</sup>, 1 h<sup>−1</sup> and 1.5 h<sup>−1</sup>) at 23 °C and RH = 50% in the test chamber. (D1 sample is a floor system made of: polyurethane solvent primer and polyurethane adhesive (see <a href="#applsci-11-04806-t003" class="html-table">Table 3</a>); significant VOCs compounds for products are in <a href="#applsci-11-04806-t001" class="html-table">Table 1</a>).</p>
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<p>The TVOC emission profiles from D2 and W1 similar floor systems (tested for480 h) for the air change rates <span class="html-italic">n</span> = 0.5 h<sup>−1</sup> at 29 °C for D1 and at 33 °C for W1 (and RH = 50% for D1 and RH = 80% for W1) and polyurethane–epoxy adhesive; D2 is made of polyurethane solvent primer and polyurethane–epoxy adhesive (see <a href="#applsci-11-04806-t003" class="html-table">Table 3</a>); significant VOCs compounds for these products are provided in <a href="#applsci-11-04806-t001" class="html-table">Table 1</a>).</p>
Full article ">Figure 13
<p>The TVOC emission profiles from W3 and W2 floor systems (tested for 480 h) for the air change rates <span class="html-italic">n</span> = 0.5 h<sup>−1</sup> at 33 °C (and RH = 80% for both) in the emission test chamber. (W3 sample is a floor system made of: polyurethane solvent primer, polymer–cement waterproofing (2), epoxy adhesive; W2 is made of: epoxy primer, polymer–cement waterproofing (1) andepoxy adhesive (see <a href="#applsci-11-04806-t003" class="html-table">Table 3</a>); significant VOCs compounds for these products are provided in <a href="#applsci-11-04806-t001" class="html-table">Table 1</a>).</p>
Full article ">Figure 14
<p>The TVOC emission profiles from D2 and D3 floor systems (tested for 480 h) for the air change rates <span class="html-italic">n</span> = 0.5 h<sup>−1</sup> at 29 °C (and RH = 50% for both) in the emission test chamber. (D3 sample is a floor system is made of: water dispersion primer and polyurethane–epoxy adhesive; D2 is made of: polyurethane solvent primer and polyurethane–epoxy adhesive (see <a href="#applsci-11-04806-t003" class="html-table">Table 3</a>); significant VOCs compounds for these products are provided in <a href="#applsci-11-04806-t001" class="html-table">Table 1</a>).</p>
Full article ">Figure 15
<p>The selected VOC emission profiles from D1 floor systems (tested for 480 h) for the air change rates <span class="html-italic">n</span> = 1 h<sup>−1</sup> at 29 °C (and RH = 50%) in the test chamber, including ethylbenzene, butanol and ethyl acetate (D1 sample is a floor system made of: polyurethane solvent primer and polyurethane adhesive (<a href="#applsci-11-04806-t002" class="html-table">Table 2</a>)).</p>
Full article ">Figure 16
<p>The selected VOCs emission profiles from D1 floor systems (tested for 480 h) for the air change rates <span class="html-italic">n</span> = 1 h<sup>−1</sup> at 29 °C (and RH = 50% for both) in the emission test chamber, including butyl acetate, o-xylene and m-p-xylene (D1 sample is a floor system made of: polyurethane solvent primer and polyurethane adhesive).</p>
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<p>The selected VOC emission profiles from W3 floor systems (testedfor480 h) for the air change rates <span class="html-italic">n</span> = 1 h<sup>−1</sup> at 33 °C (and RH = 80%) in the test chamber, including butanol, ethylbenzene, butyl acetate and m-p-xylene (W3 sample is a floor system made of: polyurethane solvent primer, polymer–cement waterproofing (2) and Epoxy adhesive).</p>
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<p>Four types of models to predict the emission of VOCs from construction materials.</p>
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<p>Chromatogram of polyurethane–epoxy adhesive—example.</p>
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15 pages, 1772 KiB  
Article
Combined Investigation of Indoor Climate Parameters and Energy Performance of a Winery
by Giorgos Panaras, Panagiotis Tzimas, Evangelos I. Tolis, Giannis Papadopoulos, Aristeidis Afentoulidis and Manolis Souliotis
Appl. Sci. 2021, 11(2), 593; https://doi.org/10.3390/app11020593 - 9 Jan 2021
Cited by 4 | Viewed by 2487
Abstract
Wineries present significant interest on a research level, combining Indoor Air Quality (IAQ) issues related with substances emitted through the wine production, as well as the need for minimizing conventional energy consumption (optimizing energy performance). In the proposed work, experimental and theoretical analyses [...] Read more.
Wineries present significant interest on a research level, combining Indoor Air Quality (IAQ) issues related with substances emitted through the wine production, as well as the need for minimizing conventional energy consumption (optimizing energy performance). In the proposed work, experimental and theoretical analyses are presented which aim to achieve both targets, that of improved indoor climate and energy performance. An extensive measurement campaign was implemented, regarding indoor climate thermal parameters, as well as concentration of substances (CO2, VOCs, NO2) affecting IAQ. The results of the parameters were exploited for the assessment of indoor climate; moreover, data from indoor thermal parameters together with values of specific parameters related to the efficiency of the individual devices were utilized in the development of the energy model. The model was used to formulate and evaluate proposals for reducing the energy consumption of the winery. The proposals include the use of Renewable Energy Sources (RES) and, in particular, the installation of a photovoltaic array on the roof of the premises. Finally, an economic and technical study was carried out to determine the performance of the suggested interventions and the expected payback period. Full article
(This article belongs to the Special Issue New Challenges for Indoor Air Quality)
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<p>Layout of the examined winery.</p>
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<p>Layout of the installation, including measuring instrumentation position.</p>
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<p>CO<sub>2</sub> concentration in office over a specific period of measurements.</p>
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<p>CO<sub>2</sub> concentration in vinification area over a specific period of measurements.</p>
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<p>Energy consumption prediction and actual values (monthly basis).</p>
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<p>(<b>a</b>) Energy consumption share of main processes (monthly basis). (<b>b</b>) Energy consumption.</p>
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<p>Monthly solar PV fraction.</p>
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23 pages, 2265 KiB  
Article
Chemical Composition and Source Apportionment of PM10 in a Green-Roof Primary School Building
by Nikolaos Barmparesos, Dikaia Saraga, Sotirios Karavoltsos, Thomas Maggos, Vasiliki D. Assimakopoulos, Aikaterini Sakellari, Kyriaki Bairachtari and Margarita Niki Assimakopoulos
Appl. Sci. 2020, 10(23), 8464; https://doi.org/10.3390/app10238464 - 27 Nov 2020
Cited by 9 | Viewed by 2470
Abstract
Research on air quality issues in recently refurbished educational buildings is relatively limited. However, it is an important topic as students are often exposed to high concentrations of air pollutants, especially in urban environments. This study presents the results of a 25-day experimental [...] Read more.
Research on air quality issues in recently refurbished educational buildings is relatively limited. However, it is an important topic as students are often exposed to high concentrations of air pollutants, especially in urban environments. This study presents the results of a 25-day experimental campaign that took place in a primary school located in a densely built-up area, which retains a green roof system (GRS). All measurements refer to mass concentrations and chemical analysis of PM10 (particulate matter less than 10 micrometers), and they were implemented simultaneously on the GRS and within the classroom (C3) below during different periods of the year. The results demonstrated relatively low levels of PM10 in both experimental points, with the highest mean value of 72.02 μg m−3 observed outdoors during the cold period. Elemental carbon (EC) was also found be higher in the ambient environment (with a mean value of 2.78 μg m−3), while organic carbon (OC) was relatively balanced between the two monitoring sites. Moreover, sulfate was found to be the most abundant water soluble anion (2.57 μg m−3), mainly originating from ambient primary SO2 and penetrating into the classroom from windows. Additionally, the crustal origin of particles was shown in trace metals, where Al and Fe prevailed (9.55% and 8.68%, respectively, of the total PM10). Nevertheless, infiltration of outdoor particles within the classroom was found to affect indoor sources of metals. Finally, source apportionment using a positive matrix factorization (PMF) receptor model demonstrated six main factors of emissions, the most important of which were vehicles and biomass burning (30.30% contribution), along with resuspension of PM10 within the classroom from human activities (29.89% contribution). Seasonal variations seem to play a key role in the results. Full article
(This article belongs to the Special Issue New Challenges for Indoor Air Quality)
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Figure 1
<p>Experimental sites of the school: (<b>a</b>) the green roof system (GRS) and (<b>b</b>) classroom C3.</p>
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<p>Mean daily concentrations of PM<sub>10</sub> indoors and outdoors during the experimental period.</p>
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<p>Indoor and outdoor OC concentrations for all sampling days.</p>
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<p>Indoor and outdoor EC concentrations for all sampling days.</p>
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<p>Chemical profiles of 6 PMF factors.</p>
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<p>Contribution percentages of each factor to the total mass of PM<sub>10.</sub></p>
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18 pages, 1932 KiB  
Article
Modeling Indoor Particulate Matter and Small Ion Concentration Relationship—A Comparison of a Balance Equation Approach and Data Driven Approach
by Miloš Davidović, Milena Davidović, Rastko Jovanović, Predrag Kolarž, Milena Jovašević-Stojanović and Zoran Ristovski
Appl. Sci. 2020, 10(17), 5939; https://doi.org/10.3390/app10175939 - 27 Aug 2020
Cited by 4 | Viewed by 2384
Abstract
In this work we explore the relationship between particulate matter (PM) and small ion (SI) concentration in a typical indoor elementary school environment. A range of important air quality parameters (radon, PM, SI, temperature, humidity) were measured in two elementary schools located in [...] Read more.
In this work we explore the relationship between particulate matter (PM) and small ion (SI) concentration in a typical indoor elementary school environment. A range of important air quality parameters (radon, PM, SI, temperature, humidity) were measured in two elementary schools located in urban background and suburban area in Belgrade city, Serbia. We focus on an interplay between concentrations of radon, small ions (SI) and particulate matter (PM) and for this purpose, we utilize two approaches. The first approach is based on a balance equation which is used to derive approximate relation between concentration of small ions and particulate matter. The form of the obtained relation suggests physics based linear regression modelling. The second approach is more data driven and utilizes machine learning techniques, and in this approach, we develop a more complex statistical model. This paper attempts to put together these two methods into a practical statistical modelling approach that would be more useful than either approach alone. The artificial neural network model enabled prediction of small ion concentration based on radon and particulate matter measurements. Models achieved median absolute error of about 40 ions/cm3 and explained variance of about 0.7. This could potentially enable more simple measurement campaigns, where a smaller number of parameters would be measured, but still allowing for similar insights. Full article
(This article belongs to the Special Issue New Challenges for Indoor Air Quality)
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Figure 1
<p>Larger area surrounding location of (<b>a</b>) School 1 (WGS84 20.556337261, 44.764855909) and (<b>b</b>) School 2 (WGS84 20.395445055, 44.799510267). Approximate location of indoor school space is marked as blue dot.</p>
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<p>Radon concentration (dotted) vs. small ion concentration (full line) in (<b>a</b>) School 1 and (<b>b</b>) School 2.</p>
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<p>Correlation matrix of quantities measured in (<b>a</b>) School 1 and (<b>b</b>) School 2. Shades of red are used for positive correlations, and shades of blue for negative correlations. (Plots were produced in Python 3.7.4 environment using libraries Seaborn 0.9.0 [<a href="#B23-applsci-10-05939" class="html-bibr">23</a>] for visualization and Pandas 0.25.2 [<a href="#B24-applsci-10-05939" class="html-bibr">24</a>] for data processing and calculations.)</p>
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<p>Comparison of a linear model based on radon and particle aggregates for School 1 (solid line) and a measurement of small ions (dotted line). Unit is [#/cm<sup>3</sup>]. Training/test score 0.44/0.49.</p>
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<p>Comparison of an artificial neural network (ANN) model based on radon and 2 PCA particle components for School 1 (solid line) and a measurement of small ions (dotted line). Unit is [#/cm<sup>3</sup>]. Training/test score 0.69/0.69.</p>
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<p>Statistics for different ANN models where several hyperparameters are changed (number of hidden layers and number of neurons per hidden layer). (<b>a</b>) R2 score training test ratio (<b>b</b>) MSE on a test set. All models have radon and 2 particulate matter related PCA components as inputs. <a href="#applsci-10-05939-f0A1" class="html-fig">Figure A1</a>b uses log10 scale.</p>
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<p>(<b>a</b>) ANN considered in this paper. Optimal model has two PCA components and 4 ReLU neurons. (<b>b</b>) Plot of a ReLU activation function.</p>
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15 pages, 1854 KiB  
Article
The Combined Effect of Indoor Air Quality and Socioeconomic Factors on Health in Northeast China
by Yu Chen and Bin Chen
Appl. Sci. 2020, 10(8), 2827; https://doi.org/10.3390/app10082827 - 19 Apr 2020
Cited by 8 | Viewed by 3574
Abstract
Research has increasingly demonstrated that complex relationships exist between residential indoor air quality, health and socioeconomic factors. However, few studies have provided a comprehensive understanding of these relationships. The purpose of this paper, therefore, was to use structural equation modeling to identify the [...] Read more.
Research has increasingly demonstrated that complex relationships exist between residential indoor air quality, health and socioeconomic factors. However, few studies have provided a comprehensive understanding of these relationships. The purpose of this paper, therefore, was to use structural equation modeling to identify the combined effect of residential indoor air quality and socioeconomic factors on occupants’ health, based on field measurement data in Northeast China. The results showed that socioeconomic status had a direct impact on the occupants’ health with the path coefficient of 0.413, whereas the effect from indoor air quality was 0.105. Socioeconomic status posed the direct effect on indoor air quality with path coefficients of 0.381. The weights of PM2.5, CO2, TVOC (Total Volatile Organic Compounds), and formaldehyde concentration to the indoor air quality were 0.813, 0.385, 0.218, and 0.142, respectively. Relative contributions of Income level, education level, and occupation prestige to socioeconomic status were 0.595, 0.551, and 0.508, respectively. Relationships between indoor air quality, socioeconomic factors and health were further confirmed based on multiple group analysis. The study defines and quantifies complex relationships between residential indoor air quality, socioeconomic status and health, which will help improve knowledge of the impacts of the residential indoor environment on health. Full article
(This article belongs to the Special Issue New Challenges for Indoor Air Quality)
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<p>The population density of Northeast China and the number of investigated residential buildings.</p>
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<p>The theoretical model used for characterizing relations between indoor air quality, socioeconomic status and health. SES—socioeconomic status; Air quality-indoor air quality; PF—physical functioning; RP—role physical; BP-bodily pain; GH—general health; VT—vitality; SF—social functioning; RE—role emotional; MH—mental health.</p>
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<p>Distribution of the average values of indoor environmental parameters. Boxplots show medians, 25 ~ 75percentiles (box) and min-max (whiskers). The red dash lines indicate the standard value recommended by the National Indoor Air Quality Standard [<a href="#B30-applsci-10-02827" class="html-bibr">30</a>].</p>
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<p>The model results inferred from the field measurement data (compared with <a href="#applsci-10-02827-f003" class="html-fig">Figure 3</a>). SES- socioeconomic status; PF-physical functioning; RP-role physical; BP-bodily pain; GH-general health; VT-vitality; SF-social functioning; RE-role emotional; MH-mental health.</p>
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11 pages, 1003 KiB  
Article
Assessment of Daily Personal PM2.5 Exposure Level According to Four Major Activities among Children
by Jiyoung Woo, Guillaume Rudasingwa and Sungroul Kim
Appl. Sci. 2020, 10(1), 159; https://doi.org/10.3390/app10010159 - 24 Dec 2019
Cited by 17 | Viewed by 3558
Abstract
Particulate matters less than 2.5 micrometers in diameter (PM2.5), whose concentration has increased in Korea, has a considerable impact on health. From a risk management point of view, there has been interest in understanding the variations in real-time PM2.5 concentrations per activity in [...] Read more.
Particulate matters less than 2.5 micrometers in diameter (PM2.5), whose concentration has increased in Korea, has a considerable impact on health. From a risk management point of view, there has been interest in understanding the variations in real-time PM2.5 concentrations per activity in different microenvironments. We analyzed personal monitoring data collected from 15 children aged 6 to 11 years engaged in different activities such as commuting in a car, visiting a commercial building, attending an education institute, and resting inside home from October 2018 to March 2019. The fraction of daily mean exposure duration per activity was 72.7 ± 18.7% for resting inside home, 27.2 ± 14.4% for attending an education institute, and 11.5 ± 9.6% and 5.3 ± 5.9% for visiting a commercial building, commuting in a car, respectively. Daily median (interquartile range) PM2.5 exposure amount was 88.9 (55.9–159.7) μg in houses and that in education buildings was 43.3 (22.9–55.6) μg. Real-time PM2.5 exposure levels varied by person and time of day (p-value < 0.05). This study demonstrated that our real-time personal monitoring and data analysis methodologies were effective in detecting polluted microenvironments and provided a potential person-specific management strategy to reduce a person’s exposure level to PM2.5. Full article
(This article belongs to the Special Issue New Challenges for Indoor Air Quality)
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Figure 1
<p>An example of the daily activity diary used to collect information of study participant’s activity pattern. (Sch: School, KG: Kinder garden, SHS: Secondhand smoke).</p>
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<p>Analysis framework for real-time PM2.5 concentration level by activity.</p>
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<p>Daily accumulated PM2.5 exposure amount per activity and per person.</p>
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18 pages, 5842 KiB  
Article
Evaluation of the Indoor Air Quality in Governmental Oversight Supermarkets (Co-Ops) in Kuwait
by Azel Almutairi, Abdullah Alsanad and Heba Alhelailah
Appl. Sci. 2019, 9(22), 4950; https://doi.org/10.3390/app9224950 - 17 Nov 2019
Cited by 7 | Viewed by 3234
Abstract
Examining the indoor air environment of public venues, especially populated supermarkets such as Co-Ops in Kuwait, is crucial to ensure that these venues are safe from indoor environmental deficits such as sick building syndrome (SBS). The aim of this study was to characterize [...] Read more.
Examining the indoor air environment of public venues, especially populated supermarkets such as Co-Ops in Kuwait, is crucial to ensure that these venues are safe from indoor environmental deficits such as sick building syndrome (SBS). The aim of this study was to characterize the quality of the indoor air environment of the Co-Ops supermarkets in Kuwait based on investigation of CO2, CO, NO2, H2S, TVOCs, and NMHC. On-site measurements were conducted to evaluate these parameters in three locations at the selected Co-Ops, and the perceived air quality (PAQ) was determined to quantify the air’s pollutants as perceived by humans. Moreover, the indoor air quality index (AQI) was constructed for the selected locations, and the ANOVA test was used to analyze the association between the observed concentrations among these environmental parameters. At least in one spot at each Co-Op, the tested environmental parameters exceeded the threshold limit set by the environmental agencies. The PAQ for Co-Op1, 2, and 3 are 1.25, 1.00, and 0.75 respectively. CO2 was significantly found in an association with CO, H2S, and TVOCs, and its indoor-outdoor concentrations were significantly correlated with R2 values ranges from 0.40 to 0.86 depending on the tested location. Full article
(This article belongs to the Special Issue New Challenges for Indoor Air Quality)
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Graphical abstract

Graphical abstract
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<p>The geographical locations of the Co-Ops under study.</p>
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<p>CO<sub>2</sub> concentration for all Co-Ops, spot S1, S2, and S3: (<b>a</b>) Morning; (<b>b</b>) Noon; (<b>c</b>) Evening.</p>
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<p>CO<sub>2</sub> concentration for Co-Op 1, S1.</p>
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<p>CO concentration for all the Co-Ops, spot S1, S2, and S3 for: (<b>a</b>) morning, (<b>b</b>) noon, and (<b>c</b>) evening.</p>
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<p>CO concentration for all the Co-Ops, spot S1, S2, and S3 for: (<b>a</b>) morning, (<b>b</b>) noon, and (<b>c</b>) evening.</p>
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<p>The H<sub>2</sub>S concentration for Co-Ops, spot S1, S2, and S3 for the morning, noon, and evening periods.</p>
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<p>The volatile organic compounds concentration: (<b>a</b>) TVOCs in spot S3; (<b>b</b>) benzene in spot S1; (<b>c</b>) styrene in spot S2.</p>
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<p>The volatile organic compounds concentration: (<b>a</b>) TVOCs in spot S3; (<b>b</b>) benzene in spot S1; (<b>c</b>) styrene in spot S2.</p>
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<p>NO<sub>2</sub> concentrations in S1 for several time periods.</p>
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<p>NMHC concentrations for S1 for different time periods.</p>
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<p>Indoor AQI for CO<sub>2</sub>, CO, VOC, and NO<sub>2</sub> for 27 sampling points. (The sampling name format is as follows: the first number indicates the Co-Op number, S is the spot location, M = morning, N = noon, and E = evening; for example, 2S3M = Co-Op 2, Spot 3, morning).</p>
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<p>Correlation of PAQ to the average CO<sub>2</sub> concentration (<b>a</b>) and the average H<sub>2</sub>S concentration (<b>b</b>).</p>
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<p>The outdoor-indoor regression of CO<sub>2</sub> for Co-Op 1: (<b>a</b>) morning; (<b>b</b>) noon; (<b>c</b>) evening.</p>
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<p>The outdoor-indoor regression of CO<sub>2</sub> for Co-Op 2: (<b>a</b>) morning; (<b>b</b>) noon; (<b>c</b>) evening.</p>
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<p>The outdoor-indoor regression of CO<sub>2</sub> for Co-Op 3: (<b>a</b>) morning; (<b>b</b>) noon; (<b>c</b>) evening.</p>
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Review

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18 pages, 957 KiB  
Review
On the Water-Soluble Organic Matter in Inhalable Air Particles: Why Should Outdoor Experience Motivate Indoor Studies?
by Regina M. B. O. Duarte and Armando C. Duarte
Appl. Sci. 2021, 11(21), 9917; https://doi.org/10.3390/app11219917 - 23 Oct 2021
Cited by 6 | Viewed by 3277
Abstract
The current understanding of water-soluble organic aerosol (OA) composition, sources, transformations, and effects is still limited to outdoor scenarios. However, the OA is also an important component of particulate matter indoors, whose complexity impairs a full structural and molecular identification. The current limited [...] Read more.
The current understanding of water-soluble organic aerosol (OA) composition, sources, transformations, and effects is still limited to outdoor scenarios. However, the OA is also an important component of particulate matter indoors, whose complexity impairs a full structural and molecular identification. The current limited knowledge on indoor OA, and particularly on its water-soluble organic matter (WSOM) fraction is the basis of this feature paper. Inspired by studies on outdoor OA, this paper discusses and prioritizes issues related to indoor water-soluble OA and their effects on human health, providing a basis for future research in the field. The following three main topics are addressed: (1) what is known about the origin, mass contribution, and health effects of WSOM in outdoor air particles; (2) the current state-of-the-art on the WSOM in indoor air particles, the main challenges and opportunities for its chemical characterization and cytotoxicity evaluation; and (3) why the aerosol WSOM should be considered in future indoor air quality studies. While challenging, studies on the WSOM fraction in air particles are highly necessary to fully understand its origin, fate, toxicity, and long-term risks indoors. Full article
(This article belongs to the Special Issue New Challenges for Indoor Air Quality)
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Figure 1
<p>Schematic representation of the range of multidimensional analytical strategies currently employed in the characterization of aerosol WSOM as a function of the level of speciation and quantification achieved. Reprinted from the work of Duarte et al. [<a href="#B50-applsci-11-09917" class="html-bibr">50</a>], under the Creative Commons Attribution (CC BY) license. Acronyms: 1D: one-dimensional; 2D: two-dimensional; DAD: diode array detector; FL: fluorescence; EEM: excitation-emission matrix fluorescence spectroscopy; PARAFAC: parallel factor analysis; FTIR: Fourier transform infrared spectroscopy; NMR: nuclear magnetic resonance spectroscopy; MS: mass spectrometry; AMS: aerosol mass spectrometry; HR-ToF-AMS: high-resolution time-of-flight AMS; PILS: particle-into-liquid sampler; MALDI: matrix-assisted laser desorption/ionization; FT-ICR MS: Fourier transform–ion cyclotron resonance MS; GC-MS: gas chromatography-MS; LC-MS: liquid chromatography-MS; LC × LC: comprehensive 2D LC; LC-LC: heart-cutting 2D LC; GC × GC: comprehensive 2D GC.</p>
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<p>Structural model of two urban aerosol WSOM samples collected under different atmospheric conditions: long-range transport from continental sources and marine and local sources, exhibiting a ratio of aliphatic –CH<sub>3</sub>, C–CH<sub>2</sub>–C, –COO, aromatic C–O, and anomeric O–C–O of 5:11:7:2:2 and 4:8:6:4:3, respectively (R<sup>1</sup> to R<sup>6</sup> = H or alkyl group; photo: aerosol WSOM, after freeze-drying). Reprinted/adapted from <span class="html-italic">Atmospheric Environment</span>, 230, R.M.B.O. Duarte, P. Duan, J. Mao, W. Chu, A.C. Duarte, K. Schmidt-Rohr, Exploring water-soluble organic aerosols structures in the urban atmosphere using advanced solid-state <sup>13</sup>C NMR spectroscopy, 117503, Copyright (2020), with permission from Elsevier.</p>
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