Multiple Gas Detection Research Articles

Dynamic Detection of Decomposition Gases in Eco-Friendly C5F10O Gas-Insulated Power Equipment by Fiber-Enhanced Raman Spectroscopy.

Dynamic detection of multiple C5F10O decomposition gases can more comprehensively and effectively evaluate the operating status of eco-friendly gas-insulated power equipment (GIPE), which is a technical support for promoting the construction of eco-friendly, low-carbon energy power systems. In this article, we propose a silicon noise suppression fiber-enhanced Raman spectroscopy (FERS) technique and design a FERS sensing system for the dynamic detection of multiple C5F10O decomposition gases. Benefiting from the effective hybrid silicon noise filtering technology, the spectrum noise of FERS can be suppressed by 90% and the system detection sensitivity can be improved by 4.22 times. Utilizing a 2 m-long antiresonant hollow-core fiber, the system achieved detection limits of 1.34 and 1.44 ppmv for CF4 and CO2, respectively, under the conditions of a laser power of 200 mW, a pressure of 0.5 MPa, and a measurement time of 120 s. Afterward, combining sample gas and density functional theory simulation, the characteristic peak positions for quantitative analysis of C5F10O decomposition gas were determined as follows: CF4: 906 cm-1, CO2: 1388 cm-1, C5F10O: 759 cm-1, CF2O: 965 cm-1, CF3H: 1117 cm-1, C2F4: 517 cm-1, C2F6: 807 cm-1, C3F6: 767 cm-1, C3F8: 780 cm-1, C3F7H: 857 cm-1, and C4F10: 770 cm-1. Finally, the sensing system conducted dynamic measurements of the partial discharge decomposition gases of the C5F10O GIPE for 5 days with a 2 h measurement interval. The content trends of C5F10O and decomposition gases CF4, CO2, C3F6, and C3F7H were obtained. These results fully demonstrate the capability of FERS technology for dynamically detecting the decomposition gases of the C5F10O GIPE.

High-Precision Low-Cost Mid-Infrared Photoacoustic Gas Sensor Using Aspherical Beam Shaping for Rapidly Measuring Greenhouse Gases

A high-precision low-cost mid-infrared photoacoustic sensor for greenhouse composite gases based on aspherical beam shaping is proposed and demonstrated. The assembled optical source module and luminous characteristics of infrared source are innovatively investigated and analyzed with aspherical beam shaping. The proposed aspherical-beam-shaping-technique could effectively reduce optical loss and enhance system sensitivity, achieving an effective power utilization ratio of a radiation source of 91% and sidewall noise ratio of 8.9%. Experiments verify the 1.7 times improvement in responsivity and 50% enhancement in minimum detection limit (MDL) on average. In terms of comprehensive greenhouse gas composites and with short integration time of 1 s, MDLs of CO2, CH4, N2O, NF3, SF6, PFC-14, and HFC-134a are 73 ppb, 267 ppb, 72 ppb, 81 ppb, 14 ppb, 9 ppb and 115 ppb, respectively. Furthermore, a 48 h continuous monitoring of H2O, CO2 and CH4 in the atmosphere is conducted and verifies the performance of the gas sensor. The developed sensor allows for the rapid route of low-cost and high-precision detection of multiple greenhouse gases.

Wavelength-modulated photoacoustic spectroscopic instrumentation system for multiple greenhouse gas detection and in-field application in the Qinling mountainous region of China

We present a sensitive and compact quantum cascade laser-based photoacoustic greenhouse gas sensor for the detection of CO2, CH4 and CO and discuss its applicability toward on-line real-time trace greenhouse gas analysis. Differential photoacoustic resonators with different dimensions were used and optimized to balance sensitivity with signal saturation. The effects of ambient parameters, gas flow rate, pressure and humidity on the photoacoustic signal and the spectral cross-interference were investigated. Thanks to the combined operation of in-house designed laser control and lock-in amplifier, the gas detection sensitivities achieved were 5.6 ppb for CH4, 0.8 ppb for CO and 17.2 ppb for CO2, signal averaging time 1 s and an excellent dynamic range beyond 6 orders of magnitude. A continuous outdoor five-day test was performed in an observation station in China’s Qinling National Botanical Garden (E longitude 108°29’, N latitude 33°43’) which demonstrated the stability and reliability of the greenhouse gas sensor.

An engineered barrier Mid-IR nBn photodetector based on III-Antimonide semiconductor alloys and its applications to use as a high-photoresponsivity optical device in multiple gas detection

An engineered barrier Mid-IR nBn photodetector based on III-Antimonide semiconductor alloys and its applications to use as a high-photoresponsivity optical device in multiple gas detection

Electronic nose based on Pd- and Pt-incorporated ZnO nanowires: a case study

Effect of incorporation of sensitizers namely palladium (Pd) and platinum (Pt) on the gas-sensing behaviour of zinc oxide (ZnO) nanowires has been studied. The specificity achieved is further studied and demonstrated for its efficacy towards the simultaneous detection of multiple gases employing the developed sensors in an electronic nose configuration. Incorporation of salt solutions containing the desired sensitizer concentration in the starting reaction mixture of hydrothermal growth has been effectively used to achieve heterostructure ZnO nanowires. Pd and Pt gets incorporated as PdO and metallic Pt, in the host matrix resulting in the formation of random heterojunctions namely p–n junction and Schottky junctions. Consequently, an increase in the work function as studied using Kelvin probe studies is observed. Utilizing statistical implements namely principal component analysis (PCA) and hierarchical cluster analysis (HCA) the discrimination of three gases namely H2, H2S and NO2 has been successfully accomplished. 3D PCA discriminates the three gases successfully with first three components exhibiting a percentage of variance of 42.32, 33.26 and 24.20%, respectively. A reasonable discrimination of H2, H2S and NO2, grouped into three clusters as evident from HCA dendrograms, was achieved using utilizing Ward’s method and Euclidian distance metric approach.

Near-Infrared Off-Axis Cavity-Enhanced Optical Frequency Comb Spectroscopy for CO2/CO Dual-Gas Detection Assisted by Machine Learning.

Cavity-enhanced direct frequency comb spectroscopy (CE-DFCS) is widely used as a highly sensitive gas sensing technology in various gas detection fields. For the on-axis coupling incidence scheme, the detection accuracy and stability are seriously affected by the cavity-mode noise, and therefore, stable operation inevitably requires external electronic mode-locking and sweeping devices, substantially increasing system complexity. To address this issue, we propose off-axis cavity-enhanced optical frequency comb spectroscopy from both theoretical and experimental aspects, which is applied to the detection of single- and dual-gas of carbon monoxide (CO) and carbon dioxide (CO2) in the near-infrared. An erbium-doped fiber frequency comb with a repetition frequency of ∼41.709 MHz is coupled into a resonant cavity with a length of ∼360 mm in an off-axis manner, exciting numerous high-order modes to effectively suppress cavity-mode noise. The performance of multiple machine learning models is compared for the inversion of a single/dual gas concentration. A few absorbance spectra are collected to build a sample data set, which is then utilized for model training and learning. The results demonstrate that the Particle Swarm Optimization Support Vector Machine (PSO-SVM) model achieves the highest predictive accuracy for gas concentration and is ultimately applied to the detection system. Based on Allan deviation, the detection limit for CO in single-gas detection can reach 8.247 parts per million by volume (ppmv) by averaging 87 spectra. Meanwhile, for simultaneous CO2/CO measurement with highly overlapping absorbance spectra, the LoD can be reduced to 13.196 and 4.658 ppmv, respectively. The proposed optical gas sensing technique indicates the potential for the development of a field-deployable and intelligent sensor system capable of simultaneous detection of multiple gases.

Two-in-One Sensor Based on PV4D4-Coated TiO2 Films for Food Spoilage Detection and as a Breath Marker for Several Diseases.

Certain molecules act as biomarkers in exhaled breath or outgassing vapors of biological systems. Specifically, ammonia (NH3) can serve as a tracer for food spoilage as well as a breath marker for several diseases. H2 gas in the exhaled breath can be associated with gastric disorders. This initiates an increasing demand for small and reliable devices with high sensitivity capable of detecting such molecules. Metal-oxide gas sensors present an excellent tradeoff, e.g., compared to expensive and large gas chromatographs for this purpose. However, selective identification of NH3 at the parts-per-million (ppm) level as well as detection of multiple gases in gas mixtures with one sensor remain a challenge. In this work, a new two-in-one sensor for NH3 and H2 detection is presented, which provides stable, precise, and very selective properties for the tracking of these vapors at low concentrations. The fabricated 15 nm TiO2 gas sensors, which were annealed at 610 °C, formed two crystal phases, namely anatase and rutile, and afterwards were covered with a thin 25 nm PV4D4 polymer nanolayer via initiated chemical vapor deposition (iCVD) and showed precise NH3 response at room temperature and exclusive H2 detection at elevated operating temperatures. This enables new possibilities in application fields such as biomedical diagnosis, biosensors, and the development of non-invasive technology.

A near-infrared multi-gas sensor based on IWTD-CEEMDAN and WOA-BiLSTM for detection of CH4 and NH3 leaked in industrial production

A multi-gas trace sensor based on tunable diode laser absorption spectroscopy (TDLAS) with two distributed feedback (DFB) lasers is designed, which was applied to measure methane (CH4) and ammonia (NH3) leaked in industrial production. The multi-frequency synchronous modulation strategy was used to drive two lasers simultaneously, where the lasers have a central wavelength of 1653.7 nm and 1512.2 nm, corresponding to the target absorption lines of CH4 and NH3 respectively. A miniaturized multi-pass gas cell (MPGC) is used as the gas absorption cell. Improved wavelet threshold denoising algorithm based on complete ensemble empirical mode decomposition with the adaptive noise (IWTD-CEEMDAN) is applied to improve the SNR of the spectral signals, and the signal-to-noise ratio (SNR) could be enhanced by approximately 26.34 dB. The concentration of CH4 and NH3 is inverted by whale optimization algorithm–bidirectional long short-term memory (WOA-BiLSTM) with a root-mean-square error (RMSE) of 0.691 ppb and 0.111 ppb respectively. The linearity, stability and response time were verified and the determination coefficients (R2) were 0.9994 and 0.9992 for CH4 and NH3. The response time of the sensor is 4.8 s, which satisfies the real-time detection demands and has the RMSE of 43.24 ppb and 11.83 ppb respectively. The limit of detection (LoD) for CH4 is 6.69 ppb with 212 s integration time, and the LoD for NH3 is 3.78 ppb with 36 s integration time, which is obtained by Allan-Werle deviation. The measurement results of CH4 and NH3 concentrations in atmosphere indicate that the sensors provide a reliable method for simultaneous real-time detection of multiple leaking gases.

Multiple Gas Detection by Cavity-Enhanced Raman Spectroscopy with Sub-ppm Sensitivity.

Accurate and sensitive detection of multicomponent trace gases below the parts-per-million (ppm) level is needed in a variety of medical, industrial, and environmental applications. Raman spectroscopy can identify multiple molecules in the sample simultaneously and has excellent potential for fast diagnosis of various samples, but applications are often limited by its sensitivity. In this contribution, we report the development of a cavity-enhanced Raman spectroscopy instrument using a narrow-line width 532 nm laser locked with a high-finesse cavity through a Pound-Drever-Hall locking servo, which allows continuous measurement in a broad spectral range. An intracavity laser power of up to 1 kW was achieved with an incident laser power of about 240 mW, resulting in a significant enhancement of the Raman signal in the range of 200-5000 cm-1 and a sub-ppm sensitivity for various molecules. The technique is applied in the detection of different samples, including ambient air, natural gas, and reference gas of sulfur hexafluoride, demonstrating its capability for the quantitative measurement of various trace components.

Design and analysis of a 2D grapheneplus (G+)-based gas sensor for the detection of multiple organic gases.

A new member of the 2D carbon family, grapheneplus (G+), has demonstrated excellent properties, such as Dirac cones and high surface area. In this study, the electronic transport properties of G+, NG+, and BG+ monolayers in which the NG+/BG+ can be obtained by replacing the center sp3 hybrid carbon atoms of the G+ with N/B atoms, were studied and compared using density functional theory and the non-equilibrium Green's function method. The results revealed that G+ is a semi-metal with two Dirac cones, which becomes metallic upon doping with N or B atoms. Based on the electronic structures, the conductivities of the 2D G+, NG+ and BG+-based nanodevices were analyzed deeply. It was found that the currents of all the designed devices increased with increasing the applied bias voltage, showing obvious quasi-linear current-voltage characteristics. IG+ was significantly higher than ING+ and IBG+ at the same bias voltage, and IG+ was almost twice IBG+, indicating that the electron mobility of G+ can be controlled by B/N doping. Additionally, the gas sensitivities of G+, NG+, and BG+-based gas sensors in detecting C2H4, CH2O, CH4O, and CH4 organic gases were studied. All the considered sensors can chemically adsorb C2H4 and CH2O, but there were only weak van der Waals interactions with CH4O and CH4. For chemical adsorption, the gas sensitivities of these sensors were considerably high and steady, and the sensitivity of NG+ to adsorb C2H4 and CH2O was greater as compared to G+ and BG+ at higher bias voltages. Interestingly, the maximum sensitivity difference for BG+ toward C2H4 and CH2O was 17%, which is better as compared to G+ and NG+. The high sensitivity and different response signals of these sensors were analyzed by transmission spectra and scattering state separation at the Fermi level. Gas sensors based on G+ monolayers can effectively detect organic gases such as C2H4 and CH2O, triggering their broad potential application prospects in the field of gas sensing.

A compact portable photoacoustic spectroscopy sensor for multiple trace gas detection

A compact, highly sensitive, and cost-effective photoacoustic spectroscopic sensor for multiple trace gas detection was reported with a self-designed compact distributed feedback laser array and a 2-channel dual phase field programmable gate array based digital lock-in amplifier, only twentieth in size and weight of the commercial instruments. The capability of the portable sensor was verified by measuring CH4 and C2H2 simultaneously. With an integrated nonlocal means algorithm denoising, noise-equivalent concentrations were achieved as 6.89 ppb for CH4 and 2.74 ppb for C2H2, respectively, corresponding to a normalized noise equivalent absorption coefficient of 1.1 × 10−10 cm−1 W/Hz−1/2, a 79 folds higher than the original data. The results demonstrate that the developed minimized sensor has the potential for sensitive and portable measurement of multiple trace gases.

Simultaneous Detection of CO and NH3 Gases at Room Temperature with an Array of ZnS Chemiresistive Sensors and the Superposition Principle.

Simultaneous detection of multiple toxic gases in the air using room temperature gas sensors is significant in low-power environmental monitoring applications. However, the low-temperature resistive gas sensors are sensitive to more than one gas, and thus, an array of gas sensors and high energy-consuming machine learning algorithms are required to predict the concentrations of the individual gases in mixed target gas. Here, we report a computationally less intensive method to predict the composition of the target gases using linear gas sensors. A sensor array consisting of two ZnS resistive gas sensors biased at different voltages in conjunction with the superposition principle is used to predict the concentration of individual gases in the binary mixture of NH3 and CO present in the air. Further, the effect of humidity on response is mitigated by formulating the sensitivity of the sensors as a function of relative humidity. The proposed algorithm predicted the concentration of the individual gases in mixed gas with a maximum absolute error of ∼15% irrespective of humidity levels, which is practically allowed in most gas sensing applications. As the superposition principle is a low-power consuming technique, the proposed approach can be used in applications where trace levels of gases in mixed targets need to be detected with energy-efficient methods.

Photoacoustic simultaneous detection of multiple trace gases for industrial park application

The determination of toxic or harmful gases in industrial parks is a challenge to monitoring exhaust contaminants due to the features of complex compositions and ubiquity. Blackbody sources play an important role in simultaneously detecting the multiple gas species in the presence of cross-interfering absorption lines due to their effective ultra-wide wavelength range. Nevertheless, the problem of lower intensity per wavelength and less stability persists as an obstacle for highly sensitive trace gas detection. In this study, a dual optical path (DOP) enhanced differential photoacoustic and spectral detection mode is developed for simultaneously detecting the multiple toxic or harmful gas through augmenting the weak effective absorption signals and suppressing the spurious coherent background noise. Two identical T-type photoacoustic resonators are introduced to enable the differential mode. Neverthelss, the pure optical approach cannot distinguish the absorption characteristics of acetylene (C<sub>2</sub>H<sub>2</sub>) with volume fraction 5 × 10<sup>–5</sup> even with the DOP enhancement, whereas emerging peaks in the differential photoacoustic (PA) mode reveal the capability of PA spectroscopy to suppress coherent noise. The results demonstrate that the differential PA signal is improved by 1.91 times that obtained by the DOP design. Methane (NH<sub>3</sub>), acetylene (C<sub>2</sub>H<sub>2</sub>) and carbon dioxide (CO<sub>2</sub>) are used to verify the performance of this DOP enhanced differential PA gas sensor, and the volume fraction of the sensitivity is found to be 7.25 × 10<sup>–7</sup> for CO<sub>2</sub>, 1.84 × 10<sup>–6</sup> for C<sub>2</sub>H<sub>2</sub>, and 1.43 × 10<sup>–6</sup> for NH<sub>3</sub> at standard temperature and pressure, which is an order of magnitude higher than the original single mode PA value. Linear PA amplitude responses ranging from 0 to 3 × 10<sup>–3</sup> in volume fraction with respect to the three target gases are observed, and the correction coefficients are all greater than 0.995. The DOP enhanced differential PA detection mode compensates for the weakness of the limited sensitivity associated with broadband spectroscopic methods based on blackbody radiator. Thus, the broadband DOP enhanced differential photoacoustic modality is demonstrated to be an effective approach to simultaneous, highly sensitive and selective detection of multiple trace gases.

Complementary Metal–Oxide–Semiconductor Compatible 2D Layered Film‐Based Gas Sensors by Floating‐Gate Coupling Effect

AbstractA 2D SnSe2 layered film‐based gas detector incorporating a floating‐gate device coupled with metal interconnect wiring structures is proposed and demonstrated for the first time. Linear amplification can be readily implemented using a coupling ratio design, which refers to the capacitance ratio between the gate and device in the sense amplifier circuits. A sensitivity of 102 mV ppm−1 can be obtained using the 2D SnSe2 layered film with a thickness of 10 nm. The 2D SnSe2 layered film‐based complementary metal–oxide–semiconductor (CMOS) gas detector features highly sensitive, wide, and adjustable dynamic ranges with a real‐time response of the sub‐ppm detection limit on NO2 gas. In addition, the synthesis process of the SnSe2 layered film can occur at a low temperature and be operated at room temperature. Furthermore, 3 × 3 gas detector arrays with peripheral circuits demonstrate the functionality of multiple gas detection simultaneously and 16 × 16 arrays with a decoder and other peripheral circuits are constructed and simulated, providing the spatial distribution of the gas concentration in a specific region. The performance of the proposed detector is comparable to that of the other state‐of‐the‐art gas sensors.

Design and structural optimization of T-resonators for highly sensitive photoacoustic trace gas detection

Thanks to the available ultra-wide wavelength range compared with broadband laser sources, the use of blackbody radiators in photoacoustic spectroscopy features the simultaneous detection of multiple gas species in the presence of cross-interfering absorption lines. The major problem associated with broadband incoherent sources is less power and less stable intensity per wavenumber than lasers and leads to limited gas detection sensitivity. In this paper, the detectivity of a broadband double optical path differential photoacoustic system was enhanced with the development of dimension-optimized high-responsivity T-resonators for simultaneous multiple trace gas detection. Enhanced Q-factor and external noise suppression level constitute dual criteria for the optimization of T-resonators. Three digital signal processing algorithms were separately investigated which further improved gas dectectability. The capability of the multiple–trace-gas detection framework was verified by measuring CO2, C2H2 and H2O simultaneously. The spectral results processed by a wavelet denoising algorithm present the best performance in terms of background noise suppression and spectral feature fidelity. [Q2.2] With the absorption enhancement of the optimized T-cells and background suppression of the wavelet denoising algorithm, a broadband differential photoacoustic system was achieved with only a 30 mW globar source and normalized noise equivalent absorption coefficient value of 4.1 × 10−10 W·cm−1·Hz−1/2 which is two orders of magnitude improvement over the original T-cell-based photoacoustic configuration. The noise equivalent detection limits were found to be 223 ppbv for CO2, 625 ppbv for C2H2 and 865 ppbv for H2O, respectively.

Non-Local Patch Regression Algorithm-Enhanced Differential Photoacoustic Methodology for Highly Sensitive Trace Gas Detection

A non-local patch regression (NLPR) denoising-enhanced differential broadband photoacoustic (PA) sensor was developed for the high-sensitive detection of multiple trace gases. Using the edge preservation index (EPI) and signal-to-noise ratio (SNR) as a dual-criterion, the fluctuation was dramatically suppressed while the spectral absorption peaks were maintained by the introduction of a NLPR algorithm. The feasibility of the broadband framework was verified by measuring the C2H2 in the background of ambient air. A normalized noise equivalent absorption (NNEA) coefficient of 6.13 × 10−11 cm−1·W·Hz−1/2 was obtained with a 30-mW globar source and a SNR improvement factor of 23. Furthermore, the simultaneous multiple-trace-gas detection capability was determined by measuring C2H2, H2O, and CO2. Following the guidance of single-component processing, the NLPR processed results showed higher EPI and SNR compared to the spectra denoised by the wavelet method and the non-local means algorithm. The experimentally determined SNRs of the C2H2, H2O, and CO2 spectra were improved by a factor of 20. The NNEA coefficient reached a value of 7.02 × 10−11 cm−1·W·Hz−1/2 for C2H2. The NLPR algorithm presented good performance in noise suppression and absorption peak fidelity, which offered a higher dynamic range and was demonstrated to be an effective approach for trace gas analysis.

Air-Gap Interrogation of Surface Plasmon Resonance in Otto Configuration.

In this study, a micromachined chip in Otto configuration with multiple air-gaps (1.86 μm, 2.42 μm, 3.01 μm, 3.43 μm) was fabricated, and the resonance characteristics for each air-gap was measured with a 980 nm laser source. To verify the variability of the reflectance characteristics of the Otto configuration and its applicability to multiple gas detection, the air-gap between the prism and metal film was adjusted by using a commercial piezoactuator. We experimentally verified that the SPR characteristics of the Otto chip configuration have a dependence on the air-gap distance and wavelength of the incident light. When a light source having a wavelength of 977 nm is used, the minimum reflectance becomes 0.22 when the displacement of the piezoactuator is about 9.3 μm.

Detection of Hazardous Gas Mixtures in the Smart Kitchen Using an Electronic Nose with Support Vector Machine

The detection of hazardous gases are essential to protect human health and safety. Nowadays, there is a great demand for the detection of multiple hazardous gases. In this study, a miniaturized electronic nose with SVM recognition models was used for the detection of carbon monoxide, methane, formaldehyde as well as their mixtures. The sensor array consisted of 6 commercial MOS sensors which were cross-sensitive to three kinds of hazardous gases. The SVM models were trained based on the features extracted by two methods in order to recognize the concentration levels of three hazardous gases. The 5-fold cross-validation was used to evaluate and compare the accuracies of different models for all target gases. The results indicated that the wavelet time scattering can extract features more effectively compared with the classic feature extraction method. The models based on the features gained by wavelet time scattering showed the accuracies of 98.73% for CO, 100% for CH4 and 97.46% for CH2O. This study provides a practical recognition method and detection platform for multi-gas sensing applications.

A miniaturized electronic nose with artificial neural network for anti-interference detection of mixed indoor hazardous gases

Indoor air quality attracted great attention for its significant threats to human health and safety, especially the potential hazardous gases in kitchens. To meet the requirements of the anti-interference detection of multiple combustible gases, in this paper, a miniaturized electronic nose was developed using MOS sensor array for semi-quantitative and anti-interference detection of carbon monoxide and methane with the interference of hydrogen and formaldehyde. The sensor array was constructed using 6 MOS sensors and cross-reaction to target and interference gases. To implement the anti-interference capability, different models were utilized and evaluated including PCA, LDA and BP-ANN. The 10-fold cross validation results indicate that BP-ANN models have the best performance than other models with the accuracy of 93.35 % for CO and 93.22 % for CH4 without interference. With the interference of H2 and CH2O, the BP-ANN model shows the accuracies of 78.92 % for CO and 89.75 % for CH4. Adding interfering samples of H2 has a more significant impact on BP-ANN models than adding that of CH2O. The results demonstrate that the proposed e-nose with the BP-ANN model can realize semi-quantitative, simultaneous and anti-interference detection of CO and CH4 in the interference environment, which provides a promising platform for gas sensing with multiple interference.

Positive vs negative resistance response to hydrogenation in palladium and its alloys

Resistive solid state sensors are widely used in multiple applications, including molecular and gas detection. The absorption or intercalation of the target species varies the lattice parameters and an effective thickness of thin films, which is usually neglected in the analyses of their transport properties in general and the sensor response in particular. Here, we explore the case of palladium-based thin films absorbing hydrogen and demonstrate that the expansion of thickness is an important mechanism determining the magnitude and the very polarity of the resistance response to hydrogenation in high resistivity films. The model of the resistance response that takes into account the modifications of thickness was tested and confirmed in three Pd-based systems with variable resistivity: thin Pd films above and below the percolation threshold, thick Pd–SiO2 granular composite films with different contents of silica, and Pd-rich CoPd alloys where resistivity depends on the Co concentration. The superposition of the bulk resistivity increase due to hydride formation and the decrease in the film resistance due to the thickness expansion provides a consistent explanation of the hydrogenation response in both continuous and discontinuous films with different structures and compositions.