Search Results (30)

The COVID-19 pandemic highlighted the urgent need for sustainable and scalable air disinfection technologies in HVAC systems, addressing the limitations of energy-intensive and chemically intensive conventional methods. This study developed and evaluated a pilot experimental installation integrating plasma chemistry and photocatalysis for airborne pathogen and pollutant mitigation. The installation, designed with a modular architecture to simulate real-world HVAC dynamics, employed a bipolar plasma ioniser, a TiO₂ photocatalytic module, and an adsorption-catalytic module for ozone abatement. Characterization techniques, including SEM and BET analysis, were used to evaluate the morphology and surface properties of the catalytic materials. Field tests in a production room demonstrated a 60% reduction in airborne microflora in three days, along with effective decomposition of ozone. The research also determined the optimal electrode geometry and interelectrode distance for stable corona discharge, which is essential for efficient plasma generation. Energy-efficient design considerations, which incorporate heat recovery and heat pump integration, achieved a 7–8-fold reduction in air heating energy consumption. These results demonstrate the potential of integrated plasma photocatalysis as a sustainable and scalable approach to enhance indoor air quality in centralised HVAC systems, contributing to both public health and energy efficiency. Full article

Over time, nanoparticles’ chemistry has shown exceptional ability to solve a wide range of problems in various fields, including the control of microbiological air quality in buildings. Herein, magnesium ferrite (MgFe₂O₄) was synthesized using coprecipitation, then characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM) and photoelectron spectroscopy (XPS). MgFe₂O₄ nanoparticles were then assessed for their ability to inhibit Escherichia coli ATCC 8739 growth and airborne bacterial viability in a laboratory atmosphere through a direct air filtration system. The material showed strong inhibitory activity against E. coli by eliminating practically all viable cells in the tested suspensions after 1 h contact time in the presence of light. Finally, the prepared air filtration setup revealed that passing air bacteria through non-woven fabric filters impregnated with MgFe₂O₄ effectively eliminates them. Thus, only 1 colony-forming unit (CFU) was obtained from 36 L of filtered air, while a control filter (without MgFe₂O₄) allowed the passage of 2.6 × 10⁵ CFU to the liquid medium. The obtained results initiate potential applications of MgFe₂O₄ nanoparticles in controlling microbiological indoor air quality (IAQ), especially in healthcare facilities where microbial resistance to antibiotics is the most notable, individuals are the most exposed, and contamination risks are the highest. Full article

Developing eco-friendly, high-performance adhesives is crucial for sustainable industrial applications but remains a significant challenge. Herein, a synergistic strategy combining core–shell hybridization and borate chemistry was employed to fabricate a multifunctional soy protein (SPI) adhesive with excellent adhesion. Specifically, a reactive core–shell hybrid (POSS-U) was synthesized via free-radical polymerization using octavinyl-POSS as the core and urushiol (U) as the shell. Sodium borate (SB) was then added as a crosslinker, along with POSS-U and SPI, to prepare the SPI/POSS-U/SB adhesive. The SPI/POSS-U/SB adhesive exhibited a 100% increase in dry shear strength (2.46 MPa) and a wet shear strength of 0.74 MPa, meeting indoor application standards. Due to the thermal shielding and char formation of POSS and SB, the peak heat release rate of the modified adhesive reduced by 25.4%, revealing excellent flame retardancy. Additionally, the modified adhesive remained mold-free for 144 h due to the antifungal properties of urushiol and boron. This work provides an innovative approach for enhancing protein-based adhesives and contributes to the advancement of multifunctional composite materials. Full article

The world has seen an increase in the frequency and severity of elevated outdoor pollution events exacerbated by the rise in distant polluting events (i.e., wildfires). We examined the intersection between indoor and outdoor air quality in an urban area using research-grade sensors to explore PM_2.5 infiltration across a variety of pollution events by testing two separate indoor environments within the same building. We confirmed prior work suggesting that indoor environments in buildings are most protective during wintertime inversion events and less so during fireworks and wildfire events. The building indoor environment protectiveness varies notably during different pollution episodes, especially those that have traveled longer distances (e.g., wildfires), and we found evidence of varied infiltration rates across PM_2.5 types. Inversion events have the lowest infiltration rates (13–22%), followed by fireworks (53–58%), and wildfires have the highest infiltration rates (62–70%), with distant wildfire events persisting longer and, therefore, infiltrating for greater durations than local-wildfire-related particle matter. The differences in PM infiltration rates were likely due to the combined effects of several factors, including varying particle size, concentration, and chemistry. Subsequently, the local wildfires had different temporal air quality impacts than distant wildfire pollution in this case. Based on these findings, indoor air quality appears more conducive to protective action and policies than outdoor air quality because the built environment may serve to shield individuals from outdoor air. Full article

In recent decades, numerous studies have indicated the substantial role semiconductors could play in photocatalytic processes for environmental applications. Materials that contain a semiconductor as a photocatalyst have a semi-permanent capacity for removing harmful gases from the ambient air. In this paper, the focus is on TiO₂. Heterogeneous photocatalysis using TiO₂ leads to the degradation of NO/NO₂, benzene, toluene, and other priority air pollutants once in contact with the semiconductor surface. Preliminary evidence indicates that TiO₂-containing construction materials and paints efficiently destroy the ozone precursors NO and NO₂ by up to 80% and 30%, respectively. Therefore, the development of innovative coatings containing TiO₂ as a photocatalyst was in the foreground of research activities. The aim of this was for coatings to be used as building and construction materials, mainly outdoors, e.g., on building façades on high-traffic roads for the degradation of priority air pollutants (NOx and volatile organic compounds) in the polluted urban atmosphere. Though there are advantages connected with the application of TiO_2, due to its band gap of 3.2 eV, these are limited. TiO₂ is effective only in the UV region (ca. 5%) of the solar spectrum with wavelengths λ < 380 nm. Hence, efforts are made here, as in many research studies, to dope TiO₂ with transition metals to increase its activity using visible light, which will extend its application to indoor environments. In our studies, experiments were conducted with 0.1% (w/w) and 1% (w/w) Mn-TiO₂ admixtures, and the ability of the modified photocatalysts to degrade NO by both solar and indoor illumination was evaluated. The surface chemistry at the air/catalyst interface, governed by the photoelectric characteristics of TiO₂ and the formation of reactive oxygen species with co-occurring redox reactions, is reviewed in this paper. The factors affecting the application of TiO₂ for the degradation of priority air pollutants as single compounds or mixtures are discussed. We investigated, particularly, the degradation of mixtures of priority compounds at typical concentrations in ambient air and confined spaces. This is a realistic approach, because pollutants are present as mixtures, rather than as individual compounds in ambient and indoor air. Moreover, organic polymers as paint constituents were found to be the primary source for carbonyl formation, e.g., formaldehyde, acetaldehyde, etc., during the heterogeneous photocatalytic processes conducted on TiO₂-enriched coatings. Full article

Ventilation may lead to a deterioration in indoor air quality in urban environments located close to roads. Understanding the differences in the chemical compositions of size-resolved particulate matter (PM) in indoor air and outdoor air could aid in assessing the health impacts of air in these settings and establishing relevant regulation policies. In this study, indoor and outdoor size-resolved PM was collected from an office in Beijing in summer (between 5 and 25 July 2020) and winter (between 5 and 31 January 2021). Its chemical components, including sulfate, nitrate, ammonium, chlorine, organic matter (OM), elemental carbon (EC), crustal materials (CM), and heavy metals (HM), were analyzed. The mean levels of indoor and outdoor PM_2.1 and PM₉ were found to be much higher than those in the guidelines for PM_2.5 and PM₁₀ outlined by the National Ambient Air Quality Standard. Moreover, the levels of PM_2.1 and PM_2.1–9 mass were higher outdoors than they were indoors. The size distributions of mass concentrations were shown to be bimodal, peaking at 0.43–0.65 μm and 4.7–5.8 μm, respectively. The most abundant chemicals were OM, nitrate, and sulfate for PM_2.1 and OM, CM, and nitrate for PM_2.1–9. We found higher percentages of sulfate, nitrate, ammonium, EC, and HM in smaller-size fractions of PM. Additionally, positive matrix factorization showed that biomass burning, secondary inorganic aerosol, coal combustion, dust, traffic, and industrial pollution were the main sources of PM during the study period. The greatest non-carcinogenic and carcinogenic hazards were found at 0.43–0.65 μm in summer and 2.1–3.3 μm in winter. Our results indicate that size-resolved PM of ambient origin may infiltrate buildings near roads to varying degrees, resulting in negative health effects. Full article

Most research on air chemistry and human health has focused on negative consequences of air pollution from cities, rural dust, mining, or industrial sites. Research on nature tourism and nature therapy, in contrast, focuses on positive benefits of air quality for physical and mental health, e.g., via “clean air clean water” holidays. Aeroanions and terpenoids in forests have received particular attention, especially in China, Japan, and Korea. We review and analyse several hundred articles published in English and Chinese. With a few recent exceptions, English-language research has tested indoor negative ion generators, and concluded that they have no measurable health benefit. It has tested terpenoids in indoor aroma marketing. Chinese-language research, in contrast, has analysed fine-scale components of outdoor environments that affect concentrations of aeroanions and terpenoids: ecosystem, latitude, altitude, temperature, proximity to water, and individual plant species. Historically, health outcomes have been taken for granted, with little rigorous testing. Air quality research has shown that aeroanions can become attached to fine water droplets, e.g., after rain in forests, or in mists produced locally by waterfalls. We hypothesise that the health benefits of aeroanions in natural environments may arise through the scavenging of airborne particulates by negatively charged mists, creating especially clean, dust-free air. We propose that this particularly clean-tasting air, contrasting strongly with polluted urban air, creates positive effects on human mental health and perhaps, also on pulmonary physical health. Mechanisms and outcomes remain to be tested. We also propose testing psychological health effects of airborne terpenoid scents from forest trees. Full article

Perfluorooctanoic acid (PFOA) in environmental matrices is increasingly being studied due to its environmental persistence, global occurrence, bioaccumulation, and associated human health risks. Some indoor environments can significantly impact the health of occupants due to pollutants in indoor air and household dust. To investigate the potential exposure of individuals to PFOA in specific confined environments, this study reports an analytical method and results concerning the determination of PFOA in household dust, used as a passive sampler. To the best of our knowledge, this paper represents one of the first studies concerning PFOA concentrations in indoor dust collected in the south of Italy, within the European region. A total of twenty-three dust samples were collected from two different areas of Sicily (Palermo and Milena), extracted, and analyzed by an UHPLC-QTOF-MS/MS system. Finally, PFOA exposure was estimated using a new index (Indoor PFOA Exposure Index, IPEX) that incorporates the PFOA levels in dust, exposure time, and the correlation between the PFOA in dust and blood. It was then compared across four different exposure groups, revealing that PFOA exposure for people working in chemistry laboratories was evaluated to be ten times higher than the exposure for homemakers. Full article

Volatile organic compounds (VOCs) from wood and wood composites are important contributors to odor profiles of indoor environments and can significantly influence human health and well-being. GC-MS/FID and gas chromatography (GC) with olfactometric detection (GC-O) are employed for the identification and characterization of odorants. Four different sample preparation methods are evaluated on wood strands and isocyanate adhesive–based oriented strand boards (OSBs) made from Pinus sylvestris L.: among these, dynamic headspace extraction thermal desorption ((dynamic) HS-TD), head space solid phase microextraction (HS-SPME), head space solid phase microextraction Arrow (HS-SPME Arrow), and liquid injection of a CH₂Cl₂ solvent extract. The olfactometric investigation revealed over 30 odor-active substances of cyclic and acyclic monoterpene, monoterpenoid ketone, monoterpenoid aldehyde, monoterpenoid alcohol, monoterpenoid ester, aliphatic aldehyde, alcohol, and acid and phenolic chemistry. Compared to liquid injection, (dynamic) HS-TD was found to result in a similar number of odorants (20 vs. 24), whereas HS SPME Arrow shows good performance with minimal instrumental effort, notably for monoterpene and aldehyde compounds. Native wood vs. OSB showed high concentrations of saturated and unsaturated aldehydes for the wood board sample. These findings demonstrate the capability of headspace methods for odorant detection and their suitability for standardization towards a database for wood and wood composites. Full article

Human beings experience a large fraction of their exposure to air pollutants in indoor environments. Air pollution is a large environmental health risk, and exposure to ambient air pollution and indoor air pollution contribute equally to the total number of fatalities worldwide. Although legislative authorities have established limit values for ambient outdoor air and stack emissions, there are inconsistent and variable national and regional limit values for gaseous substances and airborne particulate matter in the built environment (schools, homes, healthcare facilities, offices, and other public spaces). This lack of regulation is unsurprising, because indoor spaces are characterized by complex air chemistry, and their construction materials and types of activities vary significantly. The current understanding of indoor pollutants, including short-lived oxidants, degradation of VOCs, particle formation, and particle composition, is incomplete. It is necessary to identify and assess emerging pollutants and their toxicity, and to consider new consumer products and green construction materials and their impact on indoor air quality (IAQ). Learning from IAQ surveys and audit protocols, research methodologies should be regularized for cross-research comparisons. Some indoor air quality guidance and standards have been written, and several more are in development, with the international ISO 16000 series of indoor standards leading the way for improving indoor air data quality. The WHO has established some ambient air limit values which can mostly be translated into indoor limit values. The built environment needs to harmonize energy efficiency, thermal comfort and air quality standards and guidance. In this review, we discuss the next steps for improving international, regional and national standards and guidance, leading to better and more complete indoor air quality regulations. Full article

Volatile organic compounds (VOCs) emitted from building and vehicle cabin materials seriously affect indoor and in-cabin air quality, as well as human health. Previous studies revealed that some VOCs from building materials could react with ozone to affect the concentration levels of the indoor environment, but seldom refers to vehicle cabin materials. In this study, we performed experimental investigation for two kinds of vehicle cabin materials (car carpet, sealing strip) and one furniture material (medium-density fiberboard) by conducting small-scale chamber tests under two different conditions, with ozone (about 110 μg/m³) and without ozone (about 10 μg/m³), to explore the effect of in-cabin chemistry on VOC emissions. We observed the VOC concentration changes in the two scenarios and found that ozone had a significant impact on the concentrations of aldehydes and ketones while having little impact on the concentrations of benzene series. We introduced a gain ratio to quantitatively reflect the concentration changes in the presence of ozone. The gain ratio for aldehydes and ketones is greater than one, while that for the benzene series is basically around one with a small fluctuation range. This study demonstrates that ozone can react with VOCs containing unsaturated carbon–carbon bonds or carbon–oxygen bonds emitted from varied materials to produce aldehydes and ketones, which will further reduce indoor and in-cabin air quality. Full article

The battery State of Charge (SoC) is critical information to overcome agricultural robots’ limitations related to battery and energy management. Although several SoC estimation methods have been proposed in the literature, the performance of these methods has not been validated for different battery chemistries in agricultural mobile robot applications. Compared to previous work, this paper evaluates the limits of the SoC estimation using the RC model and the Thevenin model for a Lithium Iron Phosphate (LFP) battery and a Sealed Lead Acid (SLA) battery. This evaluation used a custom agricultural robot in a controlled indoor environment. Consequently, this work assessed the limitations of two ECM-based SoC estimation methods using battery packs, low-cost sensors and discharge cycles typically used in agricultural robot applications. Finally, the results indicate that the RC model is not suitable for SoC estimation for LFP battery; however, it achieved a mean absolute error (MAE) of 2.2% for the SLA battery. On the other hand, the Thevenin model performed properly for both chemistries, achieving MAE lower than 1%. Full article

The ageing of materials is an irreversible, in-time occurring complex phenomenon, which affects both wood surfaces and the coating materials. This paper focuses on the light-induced natural ageing of wood-coated surfaces in indoor conditions. Two wood species: European maple (Acer pseudoplatanus) and European walnut (Juglans regia) and two types of waxes: bees wax and Chinese wax were employed in the experiments presented in this paper. Uncoated and coated wood samples were exposed to the natural sunlight filtered by window glass in a simulated indoors natural ageing test for a total period of 7 years. Colour measurements in the CIE-Lab system and FTIR-ATR investigation were employed to evaluate the ageing phenomena. The uncoated wooden samples underwent progressive colour changes perceived as darkening for European maple and lightening for European walnut, corresponding to total colour differences values (ΔE) after 7 years of exposure of 12.54 and 11.66, respectively. Coating of wood samples with the two types of waxes differently influenced the total colour changes for the two wood species: reduced colour changes corresponding to ΔE values of 4.79–6.44 were determined for European maple, whilst increased colour changes corresponding to ΔE values of 13.80–20.83 were determined for European walnut. FTIR analysis highlighted different surface chemistry changes for the uncoated and wax-coated wood samples. Full article

Molds thrive in indoor environments, challenging the stability of building materials and occupants’ health. Diverse sampling and analytical techniques can be applied in the microbiology of buildings, with specific benefits and drawbacks. We evaluated the use of two methods, the microscopy of visible mold growth (hereinafter “mold” samples) (tape lifts) and the DNA metabarcoding of mold and dust samples (swabs), for mapping mold-damage indicator fungi in residential buildings in Oslo. Overall, both methods provided consistent results for the mold samples, where nearly 80% of the microscopy-identified taxa were confirmed by DNA analyses. Aspergillus was the most abundant genus colonizing all materials, while some taxa were associated with certain substrates: Acremonium with gypsum board, Chaetomium with chipboard, Stachybotrys with gypsum board and wood, and Trichoderma with wood. Based on the DNA data, the community composition was clearly different between the mold and the dust, with a much higher alpha diversity in the dust. Most genera identified in the mold were also detected with a low abundance in the dust from the same apartments. Their spatial distribution indicated some local spread from the mold growth to other areas, but there was no clear correlation between the relative abundances and the distance to the damages. To study mold damages, different microbiological analyses (microscopy, cultivation, DNA, and chemistry) should be combined with a thorough inspection of buildings. The interpretation of such datasets requires the collaboration of skilled mycologists and building consultants. Full article

This study investigates associations between house characteristics and chemical contaminants in house dust, collected under the nationally representative Canadian House Dust Study (2007–2010). Vacuum samples (<80 µm fraction) were analysed for over 200 synthetic organic compounds and metal(loid)s. Spearman rank correlations between contaminant concentrations in dust and presence of children and pets, types of flooring, heating styles and other characteristics suggested a number of indoor sources, pointing to future research directions. Numerous synthetic organics were significantly associated with reported use of room deodorizers and with the presence of cats in the home. Hardwood flooring, which is a manufactured wood product, emerged as a source of metal(loid)s, phthalates, organophosphate flame retardants/plasticizers, and obsolete organochlorine pesticides such as ∑DDT (but not halogenated flame retardants). Many metal(loid)s were significantly correlated with flame-retardant compounds used in building materials and heating systems. Components of heating appliances and heat distribution systems appeared to contribute heat-resistant chemicals and alloys to settled dust. Carpets displayed a dual role as both a source and repository of dust-borne contaminants. Contaminant loadings (<80 µm fraction) were significantly elevated in heavily carpeted homes, particularly those located near industry. Depending on the chemical (and its source), the results show that increased dust mass loading may enrich or dilute chemical concentrations in dust. Research is needed to improve the characterisation of hidden indoor sources such as flame retardants used in building materials and heating systems, or undisclosed ingredients used in common household products, such as air fresheners and products used for companion animals. Full article