CO2 Sensor Research Articles

Low-cost Arduino-based temperature, relative humidity and CO2 sensors - An assessment of their suitability for indoor built environments

The growing development of digital twins (DT) in AEC industry is an opportunity for deepening the control and management of energy efficiency and indoor environmental quality (IEQ). DT will demand the deployment of many sensors, and low-cost solutions are the only way to achieve that. In this study, low-cost Arduino-compatible sensors were tested considering the indoor environment of Southern European countries. Five different sensors of the following parameters were tested: temperature (T), relative humidity (RH) and carbon dioxide (CO2). The T and RH tests comprise a combination of short-term and long-term exposures over 24 months, ranging between 10 °C and 35 °C, and 50%–95%, respectively. In short-term exposure, CO2 sensors were tested in six different CO2 concentrations from 400 to 2500 ppm. For each CO2 concentration, the values were compared, varying the T (15 °C to 25 °C) and the RH (50%–90%). The results highlighted that some low-cost sensors, open-source and easily connectable to Arduino, showed an excellent behaviour and general compliance with applicable standards. SHT85 T/RH sensor, stood out in the sample, and K30 and T6713-5K CO2 sensors showed good accordance with the reference. The equivalent CO2 sensors, that use algorithms to assess the CO2 value, showed results far from the reference equipment.

CO2 monitoring system for storage of grains and seeds

The monitoring of grain and seeds characteristics is fundamental to maintain postharvest quality. Grain mass changes through CO2 levels monitoring can reduce the product deterioration by anticipating actions to maintain the grain mass quality. This study aimed to develop a CO2 monitoring system in stored grains/seeds and to analyze its efficiency. The analysis was performed in four crop species (brachiaria, sunflower, corn, and soybean) with different water content and sanity condition. The system hardware was composed of a controller micro board, CO2 sensor and data stored module. The system routine was developed in C++ language. The monitoring of CO2 and flammable gases was performed for system analysis and verification. The system monitoring developed showed efficiency in CO2 levels determination in stored grains/seeds and low-cost, being a viable and applicable tool aiming to the maintenance of postharvest quality.

Sensors Based on Nanoscale Silicon 1D Structures for Industrial, Environmental and Medical Monitoring

Article is devoted to the analysis of modern sensors based on silicon nanowires (SiNWs) to determine the influence of SiNWs synthesis parameters and their structural features on device characteristics. A modern trend in the development of electronic sensing devices is the use of various types of nanomaterials in order to increase sensor sensitivity and miniaturize of their size. 1D nanomaterials, namely SiNWs, have several advantages for sensor applications, such as a large surface-to-volume ratio and an increased rate of diffusion of the main charge carriers. Based on the literature analysis, an overview of modern SiNWs sensors was made. The advantages of silicon 1D structures were shown by comparison with other types of nanostructures. Also sensors were classified according to the methods of synthesis of SiNWs, sensor principle operation, kind of input value and types of applied modifiers. Silicon nanowires were most often synthesized by the method of metal-stimulated chemical etching, the advantages of which include the simplicity of implementation, low cost, and the ability to synthesize nanostructures with a high aspect ratio. The vapor-liquid-solid synthesis was also used, the advantages of which include the ability to be adapted to any technology of supplying a gas mixture with the target component and the possibility of obtaining nanowires with a diameter of 10 nm or less. According to the principle operation, the most of sensors developed on the basis of silicon nanowires are of electrical type (resistive, capacitive, electrochemical, diode or transistor type), optical sensors (fluorescent) are developed to a much lesser extent. Gas sensors (ethanol, oil vapor, formaldehyde, ammonia, nitrogen oxide, hydrogen, carbon dioxide,), liquid sensors (glucose, hydrogen peroxide, ethanol, heavy metal ions, pH), and physical values (humidity, temperature and illumination) have been developed on the basis of silicon 1D nanoscale structures. The following surface modifiers of nanowires were used to improve the performance characteristics: noble metal nanoparticles, metal-organic framework structures, carbon nanotubes, graphene, self-assembled monolayers, metal and metal oxide thin films. In particular, it was shown that the modification of the surface of the array of SiNWs with noble metals led to an increase in the sensitivity of the hydrogen sensor by 80%. Modification of formaldehyde sensor using reduced graphene oxide resulted in an improvement of sensor sensitivity by more than 2 times. The influence of SiNWs synthesis parameters on sensor performance characteristics was also determined. In particular, it was shown that increasing of SiNWs width from 20–30 nm to 500–600 nm led to an increase in the sensitivity of humidity sensor from 4.5 to 7.5%. Increasing the etching time caused the synthesis of longer nanowires, which improved the sensitivity of carbon dioxide sensors from 0.6 to 2.5%. Dependences established in this work will make it possible to develop the production technology of various types of sensors based on silicon nanowires with high sensitivity, selectivity, stability and operation speed.

Firefighting: Challenges of Smart PPE

The continuous research and development regarding firefighters’ personal protective equipment (PPE) has led to significant improvements in recent decades. Despite the evolution of firefighters’ PPE, every year an undesirable number of firefighters are seriously burned during firefighting operations, with some of them eventually losing their lives. The protection given by firefighters’ PPE can be further increased with the incorporation of smart textiles in the personal protective equipment, namely, wearable electronics (i.e., integrated sensors to monitor diverse parameters: heart rate, oxygen saturation, carbon dioxide detector, and setting real-time communication with a command post) and advanced materials such as phase change materials (PCMs). The evolution of firefighters’ PPE has been followed by an evolution and update in the international and national standards that specify performance requirements for firefighters’ protective clothing for structural and wildland firefighting as well as technical rescue. This study will focus on the analysis of firefighters protective clothing evolution regarding the use and integration of advanced smart materials, namely, phase change materials, taking into consideration the evolution and requirements of international and European standards as well as national legislation for firefighters’ protective clothing.

Carbon Dioxide Detectors based on Al‐ and Ni‐Doped ZnO

In this work, zinc oxide (ZnO), nickel (Ni) and aluminum (Al)‐doped ZnO nanoparticles are synthesized via an ultrasound‐assisted sol–gel technique. X‐ray diffraction analysis reveals a correlation between structural parameters (lattice parameters, crystallite size, dislocation density and micro‐strain) and the dopant ions incorporation. Scanning electron microscopy studies show changes in morphology in doped samples derived from the effect of restriction on the growth dynamics. A growth mechanism is proposed in order to explain the properties of ZnO‐based sensors. Gas sensing tests are carried out, delivering the best results as follows: an 89% sensing response at 500 ppm of carbon dioxide (CO2), 0.54 MΩ s−1 of sensitivity, and 52/48 s for average response and recovery times respectively, in the Ni‐doped ZnO sample. Additionally, selectivity evaluations for all samples are also performed. By comparing the obtained structural and morphological characteristics with the gas sensing properties of the samples, Ni‐doped ZnO samples have optimal characteristics for CO2 detection due to the high surface area and abundant oxygen vacancies resulting from the Ni incorporation. The gas sensing mechanism of each sample is also reported and discussed in detail.

Preventing unrecognised oesophageal intubation: a consensus guideline from the Project for Universal Management of Airways and international airway societies.

Across multiple disciplines undertaking airway management globally, preventable episodes of unrecognised oesophageal intubation result in profound hypoxaemia, brain injury and death. These events occur in the hands of both inexperienced and experienced practitioners. Current evidence shows that unrecognised oesophageal intubation occurs sufficiently frequently to be a major concern and to merit a co-ordinated approach to address it. Harm from unrecognised oesophageal intubation is avoidable through reducing the rate of oesophageal intubation, combined with prompt detection and immediate action when it occurs. The detection of 'sustained exhaled carbon dioxide' using waveform capnography is the mainstay for excluding oesophageal placement of an intended tracheal tube. Tube removal should be the default response when sustained exhaled carbon dioxide cannot be detected. If default tube removal is considered dangerous, urgent exclusion of oesophageal intubation using valid alternative techniques is indicated, in parallel with evaluation of other causes of inability to detect carbon dioxide. The tube should be removed if timely restoration of sustained exhaled carbon dioxide cannot be achieved. In addition to technical interventions, strategies are required to address cognitive biases and the deterioration of individual and team performance in stressful situations, to which all practitioners are vulnerable. These guidelines provide recommendations for preventing unrecognised oesophageal intubation that are relevant to all airway practitioners independent of geography, clinical location, discipline or patient type.

Wake respirometry allows breath-by-breath assessment of ventilation and CO2 production in unrestrained animals

SummaryQuantifying stress and energetic responses in animals are major challenges, as existing methods lack temporal resolution and elevate animal stress. We propose “wake respirometry,” a new method of quantifying fine-scale changes in CO2 production in unrestrained animals, using a nondispersive infrared CO2 sensor positioned downwind of the animal, i.e., in its wake. We parameterize the dispersion of CO2 in wakes using known CO2 flow rates and wind speeds. Tests with three bird species in a wind tunnel demonstrated that the system can resolve breath-by-breath changes in CO2 concentration, with clear exhalation signatures increasing in period and integral with body size. Changes in physiological state were detectable following handling, flight, and exposure to a perceived threat. We discuss the potential of wake respirometry to quantify stress and respiratory patterns in wild animals and provide suggestions for estimating behavior-specific metabolic rates via full integration of CO2 production across the wake.

Computational fluid dynamics modelling of airflow and carbon dioxide distribution inside a seminar room for sensor placement

Demand control ventilation (DCV) is a high energy efficiency ventilation strategy with control input from carbon dioxide (CO2) sensors. The measurement data quality of CO2 sensors plays a critical role in accurate determination of the indoor air quality (IAQ) and actual ventilation rate in implementation of the DCV. In this paper, the airflow field and CO2 spatial distribution in an indoor space of a seminar room seated with breathing occupants was modelled and simulated utilizing computational fluid dynamics (CFD) analysis. The airflow streamlines, airflow pressure and velocity, turbulence kinematic energy, as well as the CO2 spatial distribution in the seminar room were investigated. The locations for proper placement of the CO2 sensors in the seminar room were identified, for assuring the measurement data quality and effective DCV to achieve high energy efficiency.

Gas sensing performance of carbon monoxide sensor based on rod-shaped tin diselenide/MOFs derived zinc oxide polyhedron at room temperature

This paper introduces a high-efficiency CO gas sensor based on ZnO/SnSe2 composite film. The rod-shaped SnSe2 and polyhedral ZnO composite nanostructures were prepared by template sacrificial method and solvothermal method. The developed composite material was characterized by scanning X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and I-V testing methods, and its microstructure and composition were explored. Through comparative experiments, it was found that the response of ZnO/SnSe2 was the highest when the loading rate of SnSe2 is 25%, which was superior to pure ZnO and SnSe2 sensors. The ZnO/SnSe2 composite sensor showed excellent selectivity and good dynamic characteristics to CO at room temperature (RT). To further improve the performance of the prepared CO sensor, we studied the effect of ultraviolet (UV) light on the sensor, and the research concluded that UV light can improve the gas-sensing characteristics of the sensors. The possible CO sensing mechanism is related to the heterostructure between n-type SnSe2 and n-type ZnO nanomaterials and the photoelectrons excited by UV light.

Improvements of a low-cost CO2 commercial nondispersive near-infrared (NDIR) sensor for unmanned aerial vehicle (UAV) atmospheric mapping applications

Abstract. Unmanned aerial vehicles (UAVs) provide a cost-effective way to fill in gaps between surface in situ observations and remotely sensed data from space. In this study, a novel portable CO2 measuring system suitable for operations on board small-sized UAVs has been developed and validated. It is based on a low-cost commercial nondispersive near-infrared (NDIR) CO2 sensor (Senseair AB, Sweden), with a total weight of 1058 g, including batteries. The system performs in situ measurements autonomously, allowing for its integration into various platforms. Accuracy and linearity tests in the lab showed that the precision remains within ± 1 ppm (1σ) at 1 Hz. Corrections due to temperature and pressure changes were applied following environmental chamber experiments. The accuracy of the system in the field was validated against a reference instrument (Picarro, USA) on board a piloted aircraft and it was found to be ± 2 ppm (1σ) at 1 Hz and ± 1 ppm (1σ) at 1 min. Due to its fast response, the system has the capacity to measure CO2 mole fraction changes at 1 Hz, thus allowing the monitoring of CO2 emission plumes and of the characteristics of their spatial and temporal distribution. Details of the measurement system and field implementations are described to support future UAV platform applications for atmospheric trace gas measurements.

MEMS based metal oxide semiconductor carbon dioxide gas sensor

This paper describes the design and development of low power Micro Electro Mechanical Systems (MEMS) microheater and metal oxide semiconductor CO 2 sensor. To achieve low power, suspended plasma enhanced chemical vapour deposited SiO 2 diaphragm is used. BaTiO 3 -CuO is considered as metal oxide doped with 1% Ag and will be used as a sensing material to sense the CO 2 gas. To get the required temperature for the sensing film, three different metals namely, Platinum (Pt), Titanium (Ti) and Tungsten (W) are simulated by using COMSOL Multiphysics 5.6. The proposed microheater structure is shown to have a good temperature consistency throughout the heater's active region while consuming low power. The microheater geometry of 100 μm × 100 μm with its electro-thermal temperature results is presented here. For an applied voltage, we report a maximum average temperature of Pt i.e. ∼99.51%, Ti ∼ 97.12% and W ∼ 89.78% for 300 °C respectively. Fabrication of CO 2 sensor along with MEMS microheater had been designed and demonstrated. Energy consumed by the proposed platinum microheater geometry is 4.8 mW at 250 °C and 5.8 mW at 300 °C. The sensitivity characteristic is based on resistance sensing which has been found to be 21% for 400 ppm CO 2 gas concentration and 70% for 1000 ppm. Comparatively capacitive based sensitivity is found to be ~54% for 400 ppm and 95% for 1000 ppm. MOS Capacitive based Gas Sensor Model • Carbon dioxide has traditionally been recognized as one of the most serious atmospheric pollutants • Industries, Agriculture, Home safety and healthcare expands the marketplace for miniaturised, inexpensive gas sensors • Low power, reliable and cost-effective metal oxide semiconductor (MOS) based CO2 sensors are desirable • Sensitivity and Selectivity parameters play a very important role in designing gas sensors • Designing a microheater geometry is of great importance to achieve a preferred temperature uniformity and overall performance of a metal oxide semiconductor sensor

"Normative data for multiple breath washout outcomes in school-aged Caucasian children." Pinelopi Anagnostopoulou, Philipp Latzin, Renee Jensen, et al. Eur Respir J 2020; 55: 1901302.

The aforementioned study provided normative data for multiple breath washout outcomes in school-aged Caucasian children measured with the Exhalyzer D device (Eco Medics AG). After publication of this study, an error in the cross-sensitivity correction of the oxygen and carbon dioxide sensors in this device has been identified that leads to an overestimation of MBW outcomes [1]. Correction of this error and reanalysis of MBW data is possible with an updated software version (Spiroware version 3.3.1, Eco Medics AG). The authors of this article present updated normative data corrected for this sensor error in the research letter “Normative multiple breath washout data in school-aged children corrected for sensor error” [2], published in this issue of the European Respiratory Journal .

A Simple Method for the Analysis of Fumarolic Gases Using Response-Adjusted Sensors with a UAV

Recent developments in unmanned aerial vehicle (UAV) technology have made it possible to measure gas compositions in volcanic plumes using lightweight compact gas sensors. However, the differences in the responses of each gas sensor can be critical in estimating gas compositions based on regression scatter plots, particularly for small plumes emitted during volcanic unrest and non-eruption periods. Based on the laboratory experiments, we show that air blowers easily adjust sensor responses and improve correlation on regression scatter plots, allowing quick composition estimates without the use of mathematical applications. Applying our measurement system, lightweight compact gas sensors for H2S, SO2, CO2, and H2O, with air blowers suspended from a UAV, were used to determine the compositions of a small plume at Io-yama, Kirishima volcano, Japan. The compositions of the plume estimated by our system were reasonably consistent with those obtained by laboratory analysis of volcanic gas collected at ground level near the vent, with fluctuations in CO2 ratios and lower H2O ratios, relative to other gases, being observed. For more accurate estimations of CO2 and H2O concentrations, low humidity conditions at a distance from the fumarole are preferable for analysis of plumes diluted by ambient dry air. Our measurement system is simple, easy to set up, and useful for estimating the compositions of small passive fumarolic gas plumes during volcanic unrest and non-eruption periods, without mathematical applications.

On-chip symmetrically and asymmetrically transformed plasmonic Bragg grating formation loaded with a functional polymer for filtering and CO2 gas sensing applications

Herein, two configurations of transformed plasmonic Bragg grating (p-BG) formation loaded with a functional polymer are suggested for filtering and gas sensing applications. The symmetrically transformed p-BG formation is well suited for the development of a wide bandwidth (BW) bandstop filter. Desired filter specifications such as extinction ratio, stopband region, and stopband BW can be optimized by adjusting the geometric dimensions of the device. Polyhexamethylene biguanide (PHMB) is a functional polymer that is linearly correlated to the CO2 concentration. Therefore, it is possible to employ such material for the development of CO2 sensors. The asymmetrically transformed p-BG formation is created by moving the gold nano-blocks that are periodically arranged in the MIM waveguide away from the line of symmetry. As a result, an additional narrowband MZI resonance dip appears in the transmission continuum and is obtained along with the broadband Bragg reflection. The spectral features of the suggested devices are analyzed via the finite element method (FEM). The CO2 sensitivity of the suggested device is ∼ 226 pm/ppm for the gas concentration range of 215 ppm to 434 ppm which is considerably higher than most of the formerly suggested sensor designs.

Laboratory evaluation of low-cost air quality monitors and single sensors for monitoring typical indoor emission events in Dutch daycare centers.

Daycare centers (DCCs) are where infants and toddlers (0-4years old) spend the most time besides their homes. Given their higher susceptibility to the effects of air pollutants, as compared to older children and adults, indoor air quality (IAQ) is regarded as an essential parameter to monitor in DCCs. Recent advances in IAQ monitoring technologies have enabled the deployment of low-cost air quality monitors (LCMs) and single sensors (LCSs) to continuously monitor various indoor environments, and their performance testing should also be performed in the intended indoor applications. To our knowledge, there is no study evaluating the application of LCMs/LCSs in DCCs scenarios yet. Therefore, this study is aimed to assess the response of five types of LCMs (previously not tested) and five LCSs to typical DCCs emission activities in detecting multiple IAQ parameters, i.e., particulate matter, carbon dioxide, total volatile organic compounds, temperature, and relative humidity. These LCMs/LCSs were compared to outcomes from research-grade instruments (RGIs). All the experiments were performed in a climate chamber, where three kinds of typical activities (background; arts-and-crafts; cleaning; [in a total of 32 events]) were simulated by recruited subjects at two typical indoor climatic conditions (cool and dry [20±1°C & 40±10%], warm and humid [26±1°C & 70±5%]). Results showed that tested LCMs had the ability to capture DCCs activities by simultaneously monitoring multiple IAQ parameters, and LCMs/LCSs revealed a strong correlation with RGIs in most events (R2 values from 0.7 to 1), but, for some events, the magnitude of responses varied widely. Sensirion SCD41, an emerging CO2 sensor built on the photoacoustic sensing principle, had a more accurate performance than all tested NDIR-based CO2 sensors/monitors. In general, the study implies that the selection of LCMs/LCSs for a specific application of interest should be based on emission characteristics and space conditions.

Effect of Fermentation Duration and Dosage of EM4 on Maturity Level and Quality of Fermented Compost Fertilizer.

Livestock waste often causes pollution around the cage. Processing of livestock waste such as compost can be used as fertilizer for plants with good enough nutrient content given to plants. In order to produce good compost, it require a fermentation process. One way that is rarely used to determine the maturity level of compost is by measuring the carbon dioxide gas content in fermented compost. Measurement of carbon dioxide gas can be done using a tool in the form of a carbon dioxide sensor. The research design used was a 7 x 3 randomized block design with 2 replications, while the parameters studied were N, P, K, Moisture Content, pH, Temperature, C/N, Carbon Dioxide.

Canopy Temperature and Heat Flux Prediction by Leaf Area Index of Bell Pepper in a Greenhouse Environment: Experimental Verification and Application

Accurate classification of multilayered plants is vital to understanding the interaction of each canopy in a greenhouse environment and designing plant models based on the irradiation, canopy temperature, transpiration, and heat flux by the leaf area index (LAI). Based on the measurements from a greenhouse in operation, plant models for each LAI are discussed in this study. If the heat flux between plants and air can be accurately predicted through plant models using LAI, the heating and cooling load in various virtual greenhouses with densely planted crops can be predicted. To enhance the measurement accuracy, a temperature and humidity sensor with an aspirated shield, an infrared canopy sensor, and CO2 sensor were installed. The plant environment was measured with a portable pyranometer, porometer, ceptometer, and anemometer. The measurements were inputted to the plant models, and the canopy temperature was calculated. The canopy temperature from the models was evaluated for reliability by comparing it with field measurements (R2 = 0.98 and RMSE = 0.46). The results indicated that the big leaf model is suitable when the air circulation layer is larger than the canopy size, but when physical properties of the plant change band affect the LAI, as in a greenhouse, a multi-layer model should be considered.

Grain Storage Management at Distribution

India is an Agriculture country where 70% of the population depends on farming, the storage of grains plays a crucial role in national economy. During the grain storage, temperature, humidity and carbon dioxide and methane concentrations are important atmospheric factors that can affects the quality of the stored grain inside the go-downs and warehouses. The traditional methods are limited to simply testing the temperature and humidity conditions which are relatively backward as the other factors have to be checked independently for contributing to their effective storage. The approach of grain storage system at real-time designed by using some sensors like, DHT11, CO2 sensor, Methane sensor HC05 and Bluetooth module. These experimental results shows that the grain storage management system proposed, helps to check the nutrition levels of the grains that are being stored. This improves the rate of distribution of the grains at governmental distribution centre. The Grain storage management system gives the effective solution over the problem while distributing the grains. Hence at the end of this project the issues regarding distribution are eliminated at certain extent. Ultimately, the food availability to the people in drastic conditions and in case of natural calamities is the moto of government and this project will surely help to fulfil that moto with less manual efforts and with more efficiency.

Design, fabrication, and calibration of the Building EnVironment and Occupancy (BEVO) Beacon: A rapidly-deployable and affordable indoor environmental quality monitor

Indoor Air Quality (IAQ) monitoring is essential to assess occupant exposure to the wide range of pollutants present in indoor environments. Accurate research-grade monitors are often used to monitor IAQ but the expense and logistics associated with these devices often limits the temporal and spatial scale of monitoring efforts. More affordable consumer-grade sensors – frequently referred to as low-cost sensors – can provide insight into IAQ conditions across greater scales but their accuracy and calibration requirements need further evaluation. In this paper, we present the Building EnVironment and Occupancy (BEVO) Beacon. The BEVO Beacon is entirely open-source, including the software, hardware, and design schematics which are all provided on GitHub. We created 20 of these standalone, stationary devices which measure up to 24 parameters at a one-minute resolution of which we focus on carbon dioxide, carbon monoxide, total volatile organic compounds, temperature, and size-resolved particulate matter. We investigated the efficacy of two different calibration approaches – device-specific and environment-averaged – for these sensors as well as also provide an extensive discussion considerations for each of the sensors. Calibrated sensors performed well when compared to reference monitors or calibrated gas standards. The CO sensors yielded the best agreement (r2=0.98-0.99), followed by temperature (r2=0.89-0.99), CO2 (r2=0.62-0.99), and PM2.5 (r2=-0.13-0.91). In all cases, the device-specific calibration approach yielded the most accurate results. We evaluated our devices through a successful 11-week field study where we monitored the IAQ in participants’ bedrooms. The work we present on consumer-grade sensors adds to the existing literature by considering sensor-specific calibration techniques and analysis. The BEVO Beacon adds to the successful line of similarly developed devices by providing an open-source framework that researchers can readily adapt and modify to their own applications.

Partitioning inorganic carbon fluxes from paired O2–CO2 gas measurements in a Neotropical headwater stream, Costa Rica

The role of streams and rivers in the global carbon (C) cycle remains unconstrained, especially in headwater streams where CO2 evasion (FCO2) to the atmosphere is high. Stream C cycling is understudied in the tropics compared to temperate streams, and tropical streams may have among the highest FCO2 due to higher temperatures, continuous organic matter inputs, and high respiration rates both in-stream and in surrounding soils. In this paper, we present paired in-stream O2 and CO2 sensor data from a headwater stream in a lowland rainforest in Costa Rica to explore temporal variability in gas concentrations and ecosystem processes. Further, we estimate groundwater CO2 inputs (GWCO2) from riparian well CO2 measurements. Paired O2–CO2 data reveal stream CO2 supersaturation driven by groundwater CO2 inputs and large in-stream production of CO2. At short time scales, CO2 was diluted during storm events, but increased at longer seasonal scales. Areal fluxes in our study reach show that FCO2 is supported by greater in-stream metabolism compared to GWCO2. Our results underscore the importance of tropical headwater streams as large contributors of carbon dioxide to the atmosphere and show evaded C can be derived from both in-stream and terrestrial sources.