Toxic Gases Research Articles

Fabrication of NiO based thin film for high-performance NO2 gas sensors at low concentrations

Recent industrial and technical developments continuously result in the release of dangerous and toxic gases that have adverse effects on human life and the environment. Metal oxide nanomaterials attract attention for extremely sensitive gas sensors owing to their high surface-to-volume ratio, thermal stability, availability, and simplicity of production. Currently, p-type NiO based gas sensors are very promising, due to their outstanding repeatability, high sensitivity, low cost, and environmentally friendly characteristics. In this work, NiO prepared by low-cost hydrothermal method and its gas sensing behavior towards NO2 gas has been studied in detail. The as-prepared structure of NiO has been analyzed by using various characterization techniques like XRD, FESEM, FTIR, BET and UV–visible absorption for the study of structural, morphological and optical properties. The NiO thin film deposited on a glass substrate was analyzed under varying concentrations of NO2 at different working temperatures (100–250 °C). The sensor demonstrated a remarkable sensitivity of 45 % to 10 ppm of NO2 at low operating temperature of 200 °C. Moreover, its consistent repeatability further underscores its reliability, emphasizing its suitability for accurate and dependable NO2 detection in diverse scenarios.

Thermal degradation of self-contained breathing apparatus facepiece lenses under radiant thermal loads

The self-contained breathing apparatus is one of the most critical components of the firefighting personal protective ensemble providing protection from potentially toxic gases and products of combustion. Three models of self-contained breathing apparatus facepiece lenses meeting various editions of national standards were exposed to radiant thermal loads of 5, 10, 15, and 20 kW/m2 until thermal degradation resulted in hole formation or the test duration reached 30 min. Thermal damage was documented as time to crazing, bubbling, and hole formation. Temperature was recorded within the facepiece. There were significant differences in times to thermal damage between lenses. The facepiece lens model meeting the 2013 edition of National Fire Protection Association 1981 had significantly longer times to thermal degradation than those meeting older editions of the standard. Maximum temperatures were higher in the facepiece model meeting the 2013 edition of National Fire Protection Association 1981, likely because of the extended time the radiant load was applied.

Adsorption of small gas molecules onto boron nitride nanotubes and their Al-, Ga-, Cr- and Fe-doping derivatives for gas sensing, storage, and catalytic properties: Periodic DFT study

Based on the toxic gases and their conversion to non-toxic gases on the high potentials doping derivatives of boron nitride nanotubes (BNNTs), adsorption abilities of (5,5) and (10,0) BNNTs doped by selected dopants (Al, Ga, Cr and Fe) on small gas molecules was explored. Adsorption of small gas molecules, H2O, H2S, SO2, CO2, CO, NH3, N2O, and NO onto the pristine (5,5) and (10,0) BNNTs, their doping derivatives (Al-, Ga-, Cr- and Fe-doped (5,5) and (10,0) BNNTs) were investigated using periodic DFT method. Strong adsorptions of N2O (-4.26 eV) and SO2 (-2.56 eV) on the Cr-(5,5) and Cr-(10,0) BNNTs were found. Furthermore, the Cr-(5,5) and Cr-(10,0) BNNTs as the catalysts for N2O conversion to N2 and O2 were found. The Al- and Ga-(5,5) BNNTs, Al- and Ga-(10,0) BNNTs are suggested as the NO sensing materials and NH3 storage materials. All the suggested materials such Cr-(5,5), Cr-(10,0), Al-(5,5), Ga-(5,5), Al-(10,0) and Ga-(10,0) BNNTs could be experimentally tested for conversion, sensitivity, and storage of mentioned toxic gases in the future.

High switching characteristics and sensing-performance improvement of two-dimensional MN4 (M = Be, Mg, Ga) monolayer based nanodevices

Beryllium tetrazolium nitride (BeN4) has recently been synthesized under high pressure by laserheated diamond anvil electrodes as a new class of two-dimensional layered materials. Inspired by this, we perform first-principles calculations to investigate the electronic transport properties of MN4 (M = Be, Mg and Ga) monolayers and their gas sensing properties towards nitride-gases (NH3, NO2, NO). The obtained results show that BeN4 exhibits semi-metallic properties, MgN4 is a semiconductor with a bandgap of 0.13 eV, and the GaN4 monolayer presents strong metallic properties. Interestingly, the BeN4 and MgN4 monolayers are found to have anisotropic Dirac cones. The MN4-based 2D devices all exhibit excellent conductance as well as strong anisotropic transport, with maximum switching ratios of 107 and 104 for MgN4 and BeN4, respectively. The adsorption properties indicate that the adsorption of NH3, NO2, and NO molecules on MN4 monolayers are all chemisorptions, with the system owning much larger adsorption energies and bader charge transfers of the NO2 and NO molecules than those for the NH3 molecules, suggesting the MN4 monolayer has strong selective adsorption and responsiveness to NO2 and NO molecules. The designed gas sensor based on MgN4 show good response characteristics for NO molecules, as evidenced by the maximum current changes before and after adsorption of 30.31 µA, respectively. In summary, MN4 (M = Be, Mg and Ga) monolayers can be important candidates for high switching ratio devices and for the detection and trapping of toxic gas molecules NO.

Accumulation of Mn, Cu, and Zn in Flowers and Leaves of Catalpa bignonioides in an Urban Area Under Climate Change Conditions

Abstract Green areas are an important part of the urban landscape. Trees produce oxygen, provide shade, maintain soil moisture, and reduce the amounts of toxic gases and dust in the air. Due to the changing climate, species characteristic of other climatic zones, e.g. Catalpa bignonioides, are planted in urban parks in Poland, mainly due to the attractive appearance of the leaves and flowers. The aim of the study was to assess the content of Mn, Cu, and Zn in flowers and leaves of C. bignonioides in the urban park and to determine the value of bioconcentration coefficients (BCF) of these metals. The obtained results indicate that the flowers and leaves of C. bignonioides accumulate lesser amounts of manganese, copper, and zinc. It is a consequence of the limited bioavailability of these components in soils, due to too high pH values resulting from alkalinization of urban soils. The values of bioconcentration coefficients (BCF <1) confirm the low accumulation of Mn, Cu, and Zn in both leaves and flowers of C. bignonioides, due to the limited mobility of manganese, copper, and zinc compounds in the soils of the urban park and the low impact of falling dusts, which are the carriers of the analyzed components.

Near-infrared fluorescent probe for detection of hydrogen sulfide in water samples and food spoilage

Hydrogen sulfide (H2S) is a common toxic gas that threatens the quality and safety of environmental water and food. Herein, a new near-infrared fluorescent probe DTCM was synthesized and characterized by single crystal X-ray diffraction for sensing H2S. It exhibited a remarkable “turn-on” near-infrared (NIR) emission response at 665 nm with a remarkably massive Stokes shift of 175 nm, super-rapid detection ability (within 30 s), excellent photostability, high selectivity and sensitivity (limit of detection, LOD = 58 nM). Additionally, the probe was successfully utilized for the detection of H2S in environmental water samples. The DTCM-loaded test papers enabled convenient and real-time monitoring of H2S produced by food spoilage.

Ozone decomposition on transition-metal-atom anchored graphdiyne: Insights from computation and experiment

Transition-metal-atom anchored graphdiynes (TM@GDY, TM = Mn, Fe, Co, Ni and Cu) have already been synthesized and found applications in hydrogen evolution, nitrogen fixation and etc. By means of first-principle predictions and test experiments, we propose here that Fe@GDY and Co@GDY are efficient catalysts for the sustainable conversion of O3 to O2. These two catalysts can spontaneously chemisorb O3 with zero reaction barrier and have low O3 conversion barriers (0.31 eV and 0.19 eV, respectively). The O3 decomposition experiment in a continuous flow membrane reactor and electron paramagnetic resonance results verify that Fe@GDY and Co@GDY are efficient catalysts under humid conditions. Raman spectra prove the formation of the key Fe-O/Co-O and FeOO and CoOO intermediates. The hydrophobic nature of graphdiyne and the strongest chemisorption of O3 among tested ambient gases, make Fe@GDY and Co@GDY ideal catalysts under both dry and humid conditions. These findings would stimulate future explorations on metal anchored GDY-based catalysts for applications of toxic gas decomposition or fixation.

Solar Powered Air Purification and Cooling

This paper presents a pioneering approach to address indoor air quality challenges in urban residential spaces through the integration of solar power and advanced technology. The developed system leverages dual-axis solar tracker technology for efficient energy harvesting and storage, ensuring continuous operation. Automation driven by energy-efficient algorithms orchestrates indoor air filtration using sensors and advanced filters to remove dust and toxic gases effectively. A key innovation is the integration of renewable energy with air purification, contributing to sustainable urban practices and healthier living environments. Central to this system is an intelligent air quality monitoring framework, based on the Arduino Uno microcontroller, facilitating real-time assessment of indoor air quality. Rigorous testing and residential experiments validated the system's capability in accurately monitoring air quality indicators. The findings highlight the potential impact of this system in mitigating the transmission of airborne viruses and pollutants, thereby enhancing indoor air quality significantly. This project represents a crucial step towards creating sustainable and healthier urban living environments. Key Words: indoor air quality, solar power, air purification, intelligent monitoring, urban sustainability.

Non-combustible polymer composites with extremely high filler loading via polytetrafluoroethylene fibrillation

The incorporation of halogen-free flame retardants (FRs) into polymer matrices is a cost-effective and eco-friendly method for suppressing flames and smoke and enhancing fire safety. In energy applications, a high FR loading (e.g., >80 wt%) is often necessary owing to the excessive heat and toxic gases generated by the devices and components. However, achieving this in conventional polymer composites is significantly impeded by poor processability stemming from increased melt viscosity. This study proposes a new approach to fabricate highly loaded flame-retardant composites with an extremely high FR content of 95 wt% via fibrillation of thermally stable polytetrafluoroethylene (PTFE), which holds two different types of FRs, magnesium hydroxide (MH) and expandable graphite (EG). The hybrid composites exhibit excellent flame retardancy owing to the synergistic effects of the distinct mechanisms of the two fillers, securing a top V-0 rating in the UL-94 vertical burning test and a limiting oxygen index (LOI) exceeding 95 %. Importantly, their total heat release (THR) from the cone calorimeter test is less than 1 MJ/m2, an anomalously low value that meets the criteria for non-combustible materials (THR <8 MJ/m2). Alongside their non-combustible attributes, the composites also have high thermal conductivity, reaching up to 1.60 W/m·K, due to the presence of thermally conductive EGs. We believe that these composites and their fabrication methodology can offer new insights into the design of flame-retardant composites, which are likely to be applicable in practical applications involving severe fire hazards, such as batteries, electronics, and electric vehicles.

Bio-based P–N flame retardant with ZIF-67 in-situ growth on flexible polyurethane foam with excellent fire safety performance

The wide application of flexible polyurethane foam (FPUF) poses a giant challenge to human society in terms of fire prevention and environmental pollution. To solve this problem, the lignocellulose-based P–N flame retardant (LFPN) has been developed using mechanochemical methods. It was found that FPUF treated using LFPN exhibited good flame retardancy, but suffered from high smoke generation and toxicity. The hollow dodecahedral ZIF-67 has been used for smoke suppression catalysis, but the agglomeration phenomenon makes it inefficient. Hence, in this study, the adhesive properties of polydopamine (PDA) were utilized to assist the in-situ growth of ZIF-67. The results showed that the total smoke release rate of the treated FPUF was reduced by 40.5%. The toxic gases, such as carbon monoxide (CO), hydrogen cyanide, etc., also showed the same decreasing trend. What's more, the catalytic effect of ZIF-67 itself and the synergistic effect with LFPN gave FPUF great flame retardant and smoke inhibition properties. This novel FPUF provides a new reference for achieving smoke suppression and toxicity reduction.

The possible link between aluminum phosphide poisoning and NLRP3 inflammasome

Aluminum phosphide (AlP) is a fumigant used to control pests. However, human exposure to this substance can lead to poisoning. AlP reacts with gastric acid and water to release phosphine (PH3). This toxic gas affects the mitochondria and quickly enters the bloodstream. This gas impairs the mitochondria's ability to generate ATP, leading to oxidative stress, mitochondrial dysfunction, and damage to mitochondrial DNA (mt-DNA). Mitochondria release damage-associated molecular patterns (DAMPs) to shield cells from stress and stimulate the innate immune system.Nonetheless, if mitochondrial homeostasis is disrupted, an excessive immune response can occur, causing organ dysfunction. Mitochondrial reactive oxygen species (mt-ROS) and mt-DNA act as DAMPs. Upon recognition of DAMPs, the inflammasome is activated, causing inflammation. The nucleotide-binding domain, leucine-rich-containing family, and pyrin domain-containing-3 (NLRP3) gene on chromosome 1's extended arm encodes a protein that triggers the human inflammasome. NLRP3 is the most extensively researched inflammasome subfamily. It is essential to recognize that the pathophysiology of mitochondrial dysfunction and NLRP3 activation is complex and multifactorial, and a comprehensive approach may be needed to address both the underlying causes and downstream inflammatory responses effectively. The cGAS-STING pathway is essential for immune responses, and targeting specific nodes can be beneficial. Therapeutic approaches include small molecule drugs, biologics, vaccines, and combination therapies. Since there is a significant relationship between mitochondrial events and NLRP3 activation, targeting this inflammasome could be a promising strategy for developing antidotes for AlP poisoning.

Fast-Response and Low-Power Self-Heating Gas Sensor Using Metal/Metal Oxide/Metal (MMOM) Structured Nanowires.

With the escalating global awareness of air quality management, the need for continuous and reliable monitoring of toxic gases by using low-power operating systems has become increasingly important. One of which, semiconductor metal oxide gas sensors have received great attention due to their high/fast response and simple working mechanism. More specifically, self-heating metal oxide gas sensors, wherein direct thermal activation in the sensing material, have been sought for their low power-consuming characteristics. However, previous works have neglected to address the temperature distribution within the sensing material, resulting in inefficient gas response and prolonged response/recovery times, particularly due to the low-temperature regions. Here, we present a unique metal/metal oxide/metal (MMOM) nanowire architecture that conductively confines heat to the sensing material, achieving high uniformity in the temperature distribution. The proposed structure enables uniform thermal activation within the sensing material, allowing the sensor to efficiently react with the toxic gas. As a result, the proposed MMOM gas sensor showed significantly enhanced gas response (from 6.7 to 20.1% at 30 ppm), response time (from 195 to 17 s at 30 ppm), and limit of detection (∼1 ppm) when compared to those of conventional single-material structures upon exposure to carbon monoxide. Furthermore, the proposed work demonstrated low power consumption (2.36 mW) and high thermal durability (1500 on/off cycles), demonstrating its potential for practical applications in reliable and low-power operating gas sensor systems. These results propose a new paradigm for power-efficient and robust self-heating metal oxide gas sensors with potential implications for other fields requiring thermal engineering.

Synthesis of Ti3C2Tx nanosheets / ZnO nanowires composite material for NO2 gas sensing

NO2 is a toxic gas that poses a significant threat to the environment and human health. In this work, one-dimensional ZnO nanowires and two-dimensional layered titanium carbide (Ti3C2Tx) have been prepared by hydrothermal and selective chemical etching methods, respectively. The Ti3C2Tx/ZnO composites are synthesized by electrostatic self-assembly method. The characterization results indicate that the ZnO nanowires are uniformly dispersed on the surface of layered Ti3C2Tx to form a heterostructure. Meanwhile, the gas sensitive performance of Ti3C2Tx/ZnO composite material is investigated and compared with that of pure Ti3C2Tx. The results reveal that the composite exhibits a high selectivity as well as sensitivity with a response value (S = Rg/Ra) of 18.66 to 100 ppm NO2 at 250 ℃, which is 4.3 times higher than that of pure Ti3C2Tx. This proves that the prepared composite material is an effective sensing material for detecting NO2 gas.

Adsorption Mechanism and Regeneration Performance of Calcined Zeolites for Hydrogen Sulfide and Its Application.

Hydrogen sulfide (H2S) is a very toxic, acidic, and odorous gas. In this study, a calcined zeolite was used to investigate the adsorption performance of H2S. Among particle size, calcination temperature and time calcination temperature and time had significant effects on the adsorption capacity of H2S on the zeolite. The optimal calcination conditions for the zeolite were 332 °C, 1.8 h, and 10-20 mm size, and the maximum adsorption capacity of H2S was approximately 6219 mg kg-1. Calcination could broaden the channels, remove the adsorbed gases and impurities on the surface of zeolites, and increase the average pore size and point of zero net charge. As the zeolite adsorbed to saturation, it could be regenerated at the temperatures between 200 and 350 °C for 0.5 h. Compared with the natural zeolite, the adsorption capacities of dimethyl disulfide, dimethyl sulfide, toluene, CH3SH, CS2, CO2, and H2S were significantly higher on the calcined zeolite, while the adsorption capacity of CH4 was lower on the calcined zeolite. A gas treatment system by a temperature swing adsorption-regeneration process on honeycomb rotors with calcined zeolites was proposed. These findings are helpful for developing techniques for removing gas pollutants such as volatile sulfur compounds and volatile organic compounds to purify biogas and to limited toxic concentrations in the working environment.

Development of toxic gas sensor from anthocyanin-embedded polycaprolactone-co-polylactic acid nanofibrous mat

The colorless ammonia gas has been a significant intermediate in the industrial sector. However, prolonged exposure to ammonia causes harmful effects to organs or even death. Herein, an environmentally friendly solid-state ammonia sensor was developed utilizing colorimetric polycaprolactone-co-polylactic acid nanofibrous membrane. Pomegranate (Punica granatum L.) peel contains anthocyanin (ACN) as a naturally occurring spectroscopic probe. A mordant (potassium aluminum sulfate) is used to immobilize the anthocyanin direct dyestuff inside nanofibers, generating mordant/anthocyanin (M/ACN) coordinated complex nanoparticles. When exposed to ammonia, the color change of anthocyanin-encapsulated polycaprolactone-co-polylactic acid nanofibrous membrane from purple to transparent was examined by absorbance spectra and CIE Lab color parameters. With a quick colorimetric shift, the polycaprolactone-co-polylactic acid fabric exhibits a detection limit of 5–150 mg/L. The absorbance spectra showed a hypsochromic shift when exposed to ammonia, displaying an absorption shift from 559 nm to 391 nm with an isosbestic point of 448 nm. Scanning electron microscopy (SEM) images revealed that the polycaprolactone-co-polylactic acid nanofibers had a diameter of 75–125 nm, whereas transmission electron microscopy (TEM) images revealed that M/ACN nanoparticles exhibited diameters of 10–20 nm.

Hydrogen Sulfide Splitting into Hydrogen and Sulfur through Off-Field Electrocatalysis.

Hydrogen sulfide (H2S), a toxic gas abundant in natural gas fields and refineries, is currently being removed mainly via the Claus process. However, the emission of sulfur-containing pollutants is hard to be prevented and the hydrogen element is combined to water. Herein, we report an electron-mediated off-field electrocatalysis approach (OFEC) for complete splitting of H2S into H2 and S under ambient conditions. Fe(III)/Fe(II) and V(II)/V(III) redox mediators are used to fulfill the cycles for H2S oxidation and H2 production, respectively. Fe(III) effectively removes H2S with almost 100% conversion during its oxidation process. The H+ ions are reduced by V(II) on a nonprecious metal catalyst, tungsten carbide. The mediators are regenerated in an electrolyzer at a cell voltage of 1.05 V, close to the theoretical potential difference (1.02 V) between Fe(III)/Fe(II) and V(II)/V(III). In a laboratory bench-scale plant, the energy consumption for the production of H2 from H2S is estimated to be 2.8 kWh Nm-3 H2 using Fe(III)/Fe(II) and V(II)/V(III) mediators and further reduced to about 0.5 kWh Nm-3 H2 when employing well-designed heteropolyacid/quinone mediators. OFEC presents a cost-effective approach for the simultaneous production of H2 and elemental sulfur from H2S, along with the complete removal of H2S from industrial processes. It also provides a practical platform for electrochemical reactions involving solid precipitation and organic synthesis.

Sensing Utilities of Cesium Lead Halide Perovskites and Composites: A Comprehensive Review.

Recently, the utilization of metal halide perovskites in sensing and their application in environmental studies have reached a new height. Among the different metal halide perovskites, cesium lead halide perovskites (CsPbX3; X = Cl, Br, and I) and composites have attracted great interest in sensing applications owing to their exceptional optoelectronic properties. Most CsPbX3 nanostructures and composites possess great structural stability, luminescence, and electrical properties for developing distinct optical and photonic devices. When exposed to light, heat, and water, CsPbX3 and composites can display stable sensing utilities. Many CsPbX3 and composites have been reported as probes in the detection of diverse analytes, such as metal ions, anions, important chemical species, humidity, temperature, radiation photodetection, and so forth. So far, the sensing studies of metal halide perovskites covering all metallic and organic-inorganic perovskites have already been reviewed in many studies. Nevertheless, a detailed review of the sensing utilities of CsPbX3 and composites could be helpful for researchers who are looking for innovative designs using these nanomaterials. Herein, we deliver a thorough review of the sensing utilities of CsPbX3 and composites, in the quantitation of metal ions, anions, chemicals, explosives, bioanalytes, pesticides, fungicides, cellular imaging, volatile organic compounds (VOCs), toxic gases, humidity, temperature, radiation, and photodetection. Furthermore, this review also covers the synthetic pathways, design requirements, advantages, limitations, and future directions for this material.

Cu-MOF-derived Cu nanoparticles decorated porous N-doped biochar for low-temperature H2S desulfurization

Hydrogen sulfide (H2S) is a highly toxic and corrosive gas that poses significant risks to human health and the environment. Therefore, the development of an adsorbent capable of efficiently purifying H2S at room temperature remains a challenging task. In this study, a novel composite adsorbent with a specific surface area of 434 m2·g−1 was fabricated by modifying porous N-doped biochar with Cu nanoparticles (Cu/NBC) derived from Cu-MOFs for low-temperature desulfurization of H2S. The effect of pyrolysis temperature and the doping ratio of Cu-MOFs to biochar on the desulfurization performance of H2S for the as-prepared Cu/NBC was comprehensively investigated. Experimental results indicated that the desulfurization capability of the optimized Cu/NBC-600-1 adsorbent (synthesized at a pyrolysis temperature of 600 °C and a doping ratio of 1:1) was significantly affected by the desulfurization conditions, and the optimal conditions were determined to be at 25 °C, with 20 % oxygen content and 70 % relative humidity. Under the optimized conditions, the Cu/NBC-600-1 adsorbent exhibited a high H2S removal capacity of 158.28 mg·g−1, which was about 3.8 times higher than that of the pristine N-doped biochar. The desulfurization mechanism of the Cu/NBC composite was demonstrated to involve reactive adsorption and catalytic oxidation, resulting in the formation of elemental sulfur and copper sulfides as the main products. This study not only provides a promising approach to modify porous biochar with MOF derivatives, but also offers an effective strategy to remove low concentration H2S at room temperature.

Low temperature hydrogen production from H2S with metal tin by cyclic two-step method

Hydrogen sulfide (H2S) is not only a highly toxic and corrosive gas commonly present in the natural gas reservoir, but also valuable resource rich in hydrogen and sulfur. The Claus process is commonly used in industry to handle H2S, but it has the disadvantages of generation of SO2 and waste of hydrogen resources. Alternatively, cyclic two-step decomposition of H2S can generate H2 at low temperatures, which has been testified recently. Herein we report a method of splitting H2S into H2 and S with Sn metal in two steps at a low temperature for the first time. The experimental results demonstrate that the maximum yield of H2 can reach 33% at temperatures as low as 300 °C, and the metal Sn could be regenerated at elevated temperature. This research presents a novel approach for the decomposition of H2S to produce H2 and sulfur under relatively mild conditions, thereby opening up further opportunities for future studies on the value-added utilization of H2S.

Enhanced selectivity of novel sea urchin-like h-/m-WO3 hetero nanoflowers for highly sensitive detection of ammonia by double filtration method

Real-time monitoring of toxic gases and breath markers can be performed by metal oxide semiconductor-based chemo-resistive gas sensors due to their simple structures, low cost, and faster and better recovery and response. Due to the effective electron-hole separation, tuning the development of phase junctions of the metal oxide is an efficient method for improving their gas sensing properties. In this study, two distinct hydrothermal methods were used to synthesize h-/m-WO3 hetero-nanoflowers. In the first method, L-Cysteine was used to facilitate the formation of phase junctions between h-WO3 and m-WO3 nanostructures, whereas Thiourea was used in the second. Various characterisation approaches validated the hexagonal-monoclinic phase junction development in the nanoflowers. The sensing material fabricated using Thiourea with a concentration of 0.01M performed better than other sensors. At 350°C, the selected sample displayed outstanding ammonia sensing capacity with the experimental detection limit of 1 ppm (response=3.33). The theoretical detection limit is determined to be 27 ppb. The selectivity of the sensor towards NH3 over H2S and acetone is increased by combining the devices with a double filtration setup. The effectiveness of the selected h-/m-WO3 sensor for diagnosing kidney dysfunction was evaluated by analyzing simulated breath samples.