Review Reports - Open Access Accumulation Chambers SAGE (Surface-Air Gas Exchange)—DIY Philosophy

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for submitting the manuscript describing the SAGE (Surface–Air Gas Exchange) accumulation chamber concept and its DIY/open-hardware implementation. The topic is relevant and the effort to provide accessible documentation is appreciated. However, after careful evaluation, I recommend Reject in its current form.

The main reason is that the manuscript is presently dominated by design and implementation details, while it lacks the quantitative validation and metrological characterization required for a Sensors research Article to support scientific claims about measurement reliability and flux derivation.

Major points that prevent publication in the current form

Insufficient validation against reference methods/instruments
The manuscript does not provide a systematic comparison of measured concentrations and derived fluxes versus established reference approaches (e.g., high-grade analyzers such as LI-COR/CRDS/GC or a validated chamber system). For an instrumentation paper, inter-comparison data with clear error statistics are essential.
Lack of metrological characterization of the sensing chain
While the components and sensors are listed, the paper does not report key performance parameters expected for sensor systems: calibration procedures , drift/stability measurements, temperature and humidity dependence, and cross-sensitivities (particularly critical for MOX-type sensors). Even if flux is computed from concentration changes, these effects still directly influence dC/dt and therefore bias flux estimates unless quantified and controlled.
Method/model description requires correction and full specification
The theoretical description of concentration evolution and the equations/fitting approach appear inconsistent and need to be corrected and clarified. In addition, the flux computation workflow should be fully specified (time window selection, mixing delay exclusion, choice of linear vs non-linear fitting, QC/QA criteria, and uncertainty propagation).
Results section lacks quantitative evidence of performance and robustness
The presented results are largely qualitative and do not provide representative datasets demonstrating repeatability, reproducibility (including across units), long-term stability, and performance under realistic environmental conditions (RH/T variation, solar heating effects for transparent chambers, different surface types including water). A data-driven results section is required to substantiate the system’s practical measurement capabilities.
Overall scope/format is closer to a technical note than a research Article
As written, the manuscript reads more like an open-hardware technical report and a pointer to external documentation rather than a research paper demonstrating validated sensor-system performance. To be suitable for Sensors, the work would need to be reframed around rigorous validation and measurement science.

If the authors wish to publish in Sensors, a substantially revised (effectively new) manuscript would be needed, including: (i) corrected and complete methodology; (ii) full sensor and system metrology; (iii) comprehensive datasets over multiple conditions; (iv) intercomparison against reference instruments/methods with statistics.

Given the extent of the missing validation, these requirements go beyond what can reasonably be addressed through a standard revision, and therefore Reject is recommended.

Comments on the Quality of English Language

The English in the manuscript requires heavy polishing, as numerous typos were encountered.

Author Response

Comments 1:

Insufficient validation against reference methods/instruments
The manuscript does not provide a systematic comparison of measured concentrations and derived fluxes versus established reference approaches (e.g., high-grade analyzers such as LI-COR/CRDS/GC or a validated chamber system). For an instrumentation paper, inter-comparison data with clear error statistics are essential.

Response 1:

We agree that quantitative evidence is important. Our goal is not to validate every possible analyzer/sensor combination (the platform is intentionally open), but to demonstrate that the chamber platform itself operates reliably and produces consistent concentration dynamics suitable for standard flux derivation.
In the revised manuscript, we therefore added (i) a dedicated reliability check section and (ii) representative datasets/figures, including comparisons against a Li-COR chamber under controlled conditions and long-term field operation tests.
Regarding embedded sensors used in our autonomous configuration (CO₂ and O₂), their calibration and performance assessment are reported in our previous peer-reviewed work, which we now reference more explicitly.

Comments 2:

Lack of metrological characterization of the sensing chain
While the components and sensors are listed, the paper does not report key performance parameters expected for sensor systems: calibration procedures , drift/stability measurements, temperature and humidity dependence, and cross-sensitivities (particularly critical for MOX-type sensors). Even if flux is computed from concentration changes, these effects still directly influence dC/dt and therefore bias flux estimates unless quantified and controlled.

Response 2:

We agree that metrological aspects (calibration, drift, cross-sensitivities) are critical. Because SAGE is an open platform compatible with multiple analyzers and sensors, a full metrological characterization of all possible sensing chains is not feasible.
To address this concern practically, we clarified in the revised manuscript the default sensors used in our autonomous deployments and added a short QA/QC paragraph describing how calibration and drift are handled in practice (warm-up, periodic checks, sensor replacement schedule for electrochemical detectors, and avoiding known cross-sensitivities such as CH₄ vs sulfur compounds).
For CO₂ and O₂ sensors used here, calibration and performance evaluation are documented in our previous paper, which is now explicitly referenced.

Comments 3:

Method/model description requires correction and full specification
The theoretical description of concentration evolution and the equations/fitting approach appear inconsistent and need to be corrected and clarified. In addition, the flux computation workflow should be fully specified (time window selection, mixing delay exclusion, choice of linear vs non-linear fitting, QC/QA criteria, and uncertainty propagation).

Response 3:

We thank the reviewer for pointing out that the flux computation workflow should be fully explicit. We revised this section to clarify the equations and to state that SAGE follows established closed-chamber practice.
In addition, we added a concise description of the practical problematic (closure duration, exclusion of the initial mixing/transport period, and choice between linear vs non-linear fitting depending on the concentration dynamics), with references to existing guidelines.

Our intention is not to review the full closed-chamber theory but to ensure that users of the SAGE platform have a clear understanding.

Comment 4:

Results section lacks quantitative evidence of performance and robustness
The presented results are largely qualitative and do not provide representative datasets demonstrating repeatability, reproducibility (including across units), long-term stability, and performance under realistic environmental conditions (RH/T variation, solar heating effects for transparent chambers, different surface types including water). A data-driven results section is required to substantiate the system’s practical measurement capabilities.

Response 4:

We agree and therefore added quantitative elements in the revised version: (i) representative datasets/figures illustrating concentration dynamics and flux derivation, (ii) a comparison against a Li-COR chamber under controlled conditions, and (iii) a long-term wear test equivalent to multi-year cycling, together with one-year field operation experience.
While this does not constitute a full multi-site metrological intercomparison, it provides data-driven evidence of repeatability and operational robustness, which is the main focus of this instrumentation/platform manuscript.

Comments 5:

Overall scope/format is closer to a technical note than a research Article
As written, the manuscript reads more like an open-hardware technical report and a pointer to external documentation rather than a research paper demonstrating validated sensor-system performance. To be suitable for Sensors, the work would need to be reframed around rigorous validation and measurement science.

Response 5:

We acknowledge that the manuscript differs from a classical sensor-metrology paper focusing on a single sensing element. This is intentional: the contribution is the design and field-proven operation of an open-access automatic chamber platform (mechanics, electronics, integration, and workflow) enabling reproducible deployments and flexible sensing configurations.
We revised the introduction, discussion, and conclusions to make this scope explicit and to avoid ambiguity. In addition, we added a dedicated robustness/validation section with representative datasets to support the practical measurement capabilities of the platform.

Comments 6:

Response 6:

We understand the reviewer’s concern regarding the level of validation typically expected for a Sensors research article. We would like to clarify that the objective of this manuscript is not to provide a comprehensive review or re-validation of the closed-chamber technique itself, which has been extensively documented for more than a century, but to describe an open-access automatic chamber platform enabling researchers to implement established methodologies in a flexible and reproducible way.
Chambers with similar geometry and volume-to-surface ratios are known to exhibit comparable physical behaviour provided that leakage and excessive mixing are avoided, as extensively reported in the literature. In this context, the performance of the overall measurement chain is primarily governed by the selected analyzer or sensor and by environmental conditions (e.g. soil roughness), rather than by the chamber structure itself.
The SAGE platform was therefore designed to be compatible with both high-grade external analyzers and embedded sensors. For the latter, calibration procedures and performance assessments are reported in our previous peer-reviewed work, which is cited in the manuscript.
In the revised version, we have nonetheless strengthened the manuscript by adding representative datasets, a dedicated reliability and robustness section, and practical quality-control considerations, including limitations associated with transparent chambers. Importantly, the SAGE system allows users to implement temperature-based termination criteria to mitigate solar heating artefacts, a functionality that is not always available in commercial chamber software.
While we acknowledge that a full metrological intercomparison across all possible configurations would require a substantially different manuscript, we believe that the revised version provides a clear, honest, and practically useful contribution aligned with the scope of Sensors in the area of environmental instrumentation and open-access measurement systems.

Reviewer 2 Report

Comments and Suggestions for Authors

The article presents a well-documented and commendable open-source design for an automated chamber system (SAGE) aimed at measuring soil and water greenhouse gas fluxes. Its core strength lies in the detailed DIY approach, comprehensive documentation, and significant cost reduction compared to commercial alternatives. This makes a valuable contribution to promoting accessible, long-term monitoring. However, the technical description of the build is prioritised over a rigorous presentation of the system's scientific performance and validation data. The following points detail the main weaknesses that should be addressed to strengthen the manuscript.

The article lacks results from comparative tests of the SAGE chambers against commercial analogues or reference methods.
There is no quantitative evaluation of measurement uncertainties for the different gases (CO₂, CH₄, N₂O).
While the need for CH₄ sensor calibration is mentioned, specific calibration procedures or results are not provided.
The long-term stability of the low-cost sensors is not discussed.
Although problems with condensation and heating under a transparent cloche are described, there is no quantitative assessment of their impact on measurement accuracy.

Author Response

Comments 1:

The manuscript does not introduce new sensing principles or sensor materials. Instead, its main contribution lies in system integration, cost reduction, and open-access dissemination.

Response 1:

We agree. We would like to share our work to facilitate other scientists', and not only scientists', work. Based on our experience and on the demand of our colleagues, we feel that publishing this in a wide-audience scientific journal is more appropriate than in a technical journal. The target is to provide the ability to others to do what they want to do. It means to provide a chamber platform that accepts the sensors (internal or external) that the user wants, and the protocols that the user sets. All can be adjusted or modified. By DIY, we mean not only do the chamber yourself, but also do your measurement protocols yourself. The user is free to use sensors (internal or external) and the protocols he wants.

Comments 2:
The authors should explicitly clarify the novelty of this work compared to existing automatic chamber systems including commercial solutions and previously published DIY/open-source chambers.

Response 2:
We agree and added the corresponding statement in the introduction.

Comments 3:
The current manuscript provides very limited quantitative validation of system performance. A comparison of measured fluxes (or concentration changes) with those obtained using a reference instrument or commercial chamber system should be included.

Response 3:
We agree. SAGE chambers can work with the external analyzers, as a usual commercial setup. Its volume by surface ratios is very close to the Li-COR chambers. If working with an external analyzer, the difference would result from some airtightness fault or excessive air mixing only. But these points were closely watched and checked. The air tightness was checked for over one year in the real conditions, and the internal air mixing was checked against à Li-COR chamber and can be adjusted by fan speed control accessible by specific commands, which means that it can be adjusted by the user for the use they want.

Comments 4:
Quantitative metrics such as repeatability, uncertainty, or variability (e.g., standard deviation, coefficient of variation) should be included.

Response 4:
We agree, we are adding two paragraphs in the discussion. At the same time, the repeatability depends on the sensors’ repeatability and the airtightness of the chamber. Sensors can be replaced by the user, so the sensors’ repeatability used in our group is not so pertinent. The main sensors (CO₂ and O₂) were checked and described in our previous paper, which presents the nomad chambers.

Comments 5:
-A brief discussion on sensor drift and long-term stability with this chamber should be included.

Response 5:
We agree, a corresponding check description was added.

Comments 6:
-Figures and block diagrams summarizing system architecture and measurement workflow should be included.
There are already two figures (Figure 5 and Figure 6) representing two main configurations. It is impossible to represent all possible configurations. Measurement workflow depends on the chosen configuration; it is also impossible to summarize it all.

Response 6:

We are adding the corresponding workflow to the main configurations (serial and autonomous).

Comments 7:

The manuscript presents theoretical equations for closed-chamber flux estimation. However, these equations are not clearly linked to the actual SAGE chamber design or to any experimental results. The authors should demonstrate the application of the proposed equations using measured data from the developed chambers and clearly show how the fluxes are derived in practice.

Response 7:

We are adding some statements about it. However, the flux derivation is not tied to SAGE’s particularity but to a widely-used and widely-described closed chamber technique. Users can also use a free Li-COR “SoilFluxPro” software if it is their wish.

Comments 8:
- A table summarizing sensor type, measurement range, accuracy, and calibration requirements should be included.

Response 8:

We are sorry, but this demand is impossible to be satisfied. We are using some sensors, but a lot of other sensors can be used with SAGE chambers, and it will be impossible to describe them all. Any user can use whatever they want. It is not our scope to push scientists to use a particular sensor rather than another. We are adding a corresponding statement to the introduction. The embedded sensors we are using were already described and compared in our previous publication cited in the manuscript.

Comments 9:
Real-time sensor data obtained from the proposed chamber should be presented and compared with data from other chamber systems to clearly demonstrate the advantages of the proposed design.

Response 9:
We agree. It is already the case in Figure 2, and we are adding some other graphs (Figures 3 and 4). However, the advantage of SAGE chambers does not lie in the data. Commercial data is of good quality; it is not our point. The advantage of SAGE chambers is in some possible configurations and options not available commercially, but mainly in the open-access character. SAGE chambers are an open-platform allowing users to employ the sensors and protocols they want.

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript presents the design and implementation of an open-access, automatic closed-chamber system (SAGE) for monitoring soil– and water–atmosphere gas exchanges. The work focuses on hardware design, electronics integration, and system versatility rather than on the development of new sensing principles. However, it reads more like a detailed technical report or user manual than a scientific article. Therefore, it requires substantial revision and clarification before being considered for publication.

- The manuscript does not introduce new sensing principles or sensor materials. Instead, its main contribution lies in system integration, cost reduction, and open-access dissemination.

- The authors should explicitly clarify the novelty of this work compared to existing automatic chamber systems including commercial solutions and previously published DIY/open-source chambers.

- The current manuscript provides very limited quantitative validation of system performance. A comparison of measured fluxes (or concentration changes) with those obtained using a reference instrument or commercial chamber system should be included.

- Quantitative metrics such as repeatability, uncertainty, or variability (e.g., standard deviation, coefficient of variation) should be included.

- A brief discussion on sensor drift and long-term stability with this chamber should be included.

- Figures and block diagrams summarizing system architecture and measurement workflow should be included.

- The manuscript presents theoretical equations for closed-chamber flux estimation. However, these equations are not clearly linked to the actual SAGE chamber design or to any experimental results. The authors should demonstrate the application of the proposed equations using measured data from the developed chambers and clearly show how the fluxes are derived in practice.

- A table summarizing sensor type, measurement range, accuracy, and calibration requirements should be included.

- Real-time sensor data obtained from the proposed chamber should be presented and compared with data from other chamber systems to clearly demonstrate the advantages of the proposed design.

Author Response

Comments 1:

The article lacks results from comparative tests of the SAGE chambers against commercial analogues or reference methods.

Response 1:

Indeed, the methods are not discussed as SAGE chambers, using a well-known and commonly used technique of the closed chambers. We have tested SAGE chambers for over one year on an agricultural plot, along with other chambers (not commercial but made by our colleagues from INRAe. The raw concentration measurement was not the same as the chamber volume to covered surface of SAGE and INRAe chambers was not the same. The data quality and calculated flux were higher with SAGE as the INRAe chambers are aged and their airtightness may be compromised. Corresponding sentences and graphs were added to the discussion.

Comments 2:

There is no quantitative evaluation of measurement uncertainties for the different gases (CO₂, CH₄, N₂O).

Response 2:

We agree. There are three sources of uncertainty in the flux determinations.
- Soil or water fluxes stability. Any flux variation during the measurement biases the calculated flux. This issue is very important for transparent cloche-equipped chambers as the CO2 absorption depend of the photosynthetic activity that changes with the solar radiation. Any cloud passage or other shadowing is immediately perceptible in the recorded concentration.
- Gas concentration measurement uncertainty. This comes from the gas analyzers. SAGE chambers can be used with a lot of different gas analyzers. For each monitored gas, several analyzers are usable. This is a common concern for every closed chamber system and depends on the used analyzer rather than the chambers themselves. As embedded sensors, for CO2 and O2, we used the same sensors as for the nomad chambers, and we checked them and presented them in our previous paper cited in the manuscript. Sensors for NH3 and SO2 were not checked, but were used only as a detector rather than a quantitative analyzer. We used the manufacturer's specifications. The CH4 sensor was not used due to the possible presence of sulfur compounds. The detailed specifications and calibration protocol are given in the cited paper. In general, our manuscript describes the DIY chamber. We provide a base that can be used with different sensors and analyzers. We do not intend to impose anything, and everything can be adapted or modified. - Volume of the entrapped air during the measurements. This is effectively the adopted chamber system concern. Of course, the air tightness should be preserved. However, due to the pressure equilibration, the internal volume can change. Water evaporation or internal air temperature change forces volume change at constant pressure. This volume also includes the air leading pipes, pneumatic multiplexer, and gas analyzer internal volume, if an external analyzer is used. However, the main uncertainty comes from the soil surface. Indeed, the cloche is covering a collar inserted into the soil, and when the soil surface is not perfectly flat, it may be hard to estimate the volume inside the collar… This strong source of uncertainty concerns mostly the soil, not the water. However, it is not SAGE chambers' issue, but a common closed chambers issue, and we did not discuss it in detail. Yet, a corresponding statement is added to the discussion.

Comments 3:

While the need for CH₄ sensor calibration is mentioned, specific calibration procedures or results are not provided.

Response 3:
The specific calibration protocol is given by the reference cited in the manuscript. We point it out specifically in the revised version.

Comments 4:

The long-term stability of the low-cost sensors is not discussed.

Response 4
We agree. The low-cost sensors' stability is different for each sensor. We already stated that several low-cost sensors use the same technology as the biggest sensors. For example, the NDIR low-cost sensors. We are using the SCD-30, a CO2 low-cost sensor that shows roughly the same long-term stability as the biggest IR analyzers. Again, a lot of different sensors can be used, and it is impossible to characterize them all. Low-cost does not mean “bad”. However, you have also “bad” sensors, which are often cheap. We can also find rather expletive sensors that are not good, but not good at all…Our manuscript is centered on the SAGE chamber platform and DIY philosophy.

Comments 5:

Although problems with condensation and heating under a transparent cloche are described, there is no quantitative assessment of their impact on measurement accuracy.

Response 5:
We agree. However, it is a common, well-known problem of the transparent cloche chambers; we are citing a paper raising these problems, which are not specific to SAGE chambers. Quantitative assessment was highly tied to the covered vegetation type (shadowed solar radiation for the photosynthesis and solar heating of a vegetated surface). It would be only valid for a specific place at a specific moment. Some vegetation at some moment may dry and disappear, or, on the contrary, benefit from the raised temperature and develop faster than outside the chamber. In both case there is a perturbation due to the chamber's presence.

Reviewer 4 Report

Comments and Suggestions for Authors

Thanks to the authors for an interesting manuscript. The issue raised in the study is important. The physical principles of operation of chambers and sensor systems presented and discussed in the manuscript are clear and justified.

I would like to add that such chambers are important not only for studying gas emission from soil and vegetation. The introduction chapter should cover more topics.

Geological prospecting is more important than agricultural applications of developed SAGE chambers. We can often observe how geologists dig holes in earth and cover them with rags to accumulate the appropriate amount of target gas. A lot of research takes place in hard-to-reach areas - deserts, jungles. The measurement type of gases and their dynamics are also important. For example, hydrogen is a gas that indicates on place of possible earthquakes. The amount of methane and hydrocarbons concentrations is important for the search for oil deposits. Moreover, exploration directly in fields is very important for finding the contours of the deposit for effective well drilling. There are also many applications for searching for emissions of radioactive gases such as Radon from the earth.

In general, I would look at the application of the developed SAGE chamber a little more broadly.

The use of inexpensive sensor systems indicated in the manuscript is also appropriate, since in practical geology, methods that allow one to determine the type of gas and its concentration using literally available means are highly valued. Removing (evacuating) cameras from hard-to-reach places is difficult, and cost starting plays a major role here.

Author Response

Comments 1:

Response 1:

We can only agree, thank you.

Comments 2:

I would like to add that such chambers are important not only for studying gas emission from soil and vegetation. The introduction chapter should cover more topics.

In general, I would look at the application of the developed SAGE chamber a little more broadly.

Response 2:

We agree, any gas exchange between soil or water can be monitored using SAGE chambers with an appropriate gas analyzer. We added two references to the geological prospecting and gas leak detection use in the introduction. However, this is not the field of our expertise, and we can't discuss this point in detail.

Comments 3:

Response 3:

We agree, lowering the cost and simplifying the installation allows a broader use of the chambers.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The revision improves presentation, but the manuscript is still not acceptable as a Sensors Article due to unresolved methodological inconsistency and insufficient validation/metrology.

Correct the core model/equations: the manuscript states exponential/asymptotic concentration evolution, yet the equation set remains internally inconsistent. Provide the correct model, consistent equations, and full variable definitions/units.
Specify the flux algorithm unambiguously: mixing delay exclusion, time-window selection, fitting model (linear vs exponential), regression method, residual checks, and cycle acceptance/rejection criteria.
Provide a complete QC/QA workflow: explicit flags (leaks, poor mixing, curvature), thresholds, and handling rules; include a flowchart or checklist.
Make the Li-COR comparison a real validation: report N (paired cycles), number of days/sites, surfaces (soil/water), environmental ranges; ensure identical fitting/QC rules.
Report proper agreement statistics: bias, RMSE/MAE, confidence intervals; add an agreement analysis (e.g., Bland–Altman). A single scatter plot is not validation.
Show time-series overlays: at least one representative cycle where SAGE and Li-COR concentration curves and derived flux are compared under identical closure timing.
Metrology for each quantitative channel (minimum CO₂ and O₂): calibration procedure/traceability, response time (t90), noise/precision, drift, RH/T dependence, and cross-sensitivity.
If CH₄/NH₃/H₂S channels are kept: clearly state whether they are quantitative or only indicative detectors; provide interference/cross-sensitivity testing (RH, sulfur poisoning, etc.) and remove unsupported quantitative claims.
Provide a full flux uncertainty budget: propagate uncertainties from dC/dt (fit + noise + drift), V and S, T/P corrections, timing, mixing delay, leaks/venting; report flux with confidence intervals.
Quantify leak rate and pressure equilibration: provide a measured leak rate (pressure decay or tracer test) and show pressure differential control during closure.
Quantify mixing: demonstrate mixing time constant vs fan speed; show that mixing is fast relative to closure duration; discuss bias if not.
Quantify transparent chamber heating bias and mitigation: provide data on temperature rise during closure under sun/wind and demonstrate an effective mitigation protocol (not only discussion).

Mandatory reproducibility deliverables: deposit raw datasets used for validation figures + analysis code (flux fitting + QC) + metadata (conditions, chamber configuration, sensor versions) with clear versioning/DOI.

Comments on the Quality of English Language

The English in the manuscript requires some improvements.

Author Response

Comments 1: The revision improves presentation, but the manuscript is still not acceptable as a Sensors Article due to unresolved methodological inconsistency and insufficient validation/metrology.

Response 1: We thank the reviewer for the careful evaluation. We acknowledge that the first version did not sufficiently clarify the intended scope of the manuscript. This work is presented as an open-access environmental instrumentation platform paper. It does not aim to re-validate the closed-chamber methodology itself, which is extensively documented in the literature, but to describe the design, integration, and field operation of the SAGE platform. In the revised manuscript, we clarified the theoretical framework, corrected the equations, and added representative datasets and a dedicated reliability section illustrating practical field operation. We believe these additions strengthen the manuscript within the intended scope.
Comments 2: Correct the core model/equations: the manuscript states exponential/asymptotic concentration evolution, yet the equation set remains internally inconsistent. Provide the correct model, consistent equations, and full variable definitions/units.

Response 2: We thank the reviewer for identifying the inconsistency in the previous version. Equation (3) has been corrected in the revised manuscript, and the relevant variables used in the theoretical section are now clearly defined in the text. We also clarified how mixing ratios are handled in the flux calculation framework.

Comments 3: Specify the flux algorithm unambiguously: mixing delay exclusion, time-window selection, fitting model (linear vs exponential), regression method, residual checks, and cycle acceptance/rejection criteria.

Response 3: We appreciate the reviewer’s request for clarification. In the revised manuscript, we explicitly describe the practical considerations applied during flux computation: exclusion of the initial data points to avoid mixing artifacts, evaluation of concentration evolution (linear versus asymptotic), and selection of the fitting model accordingly. We emphasize that these elements depend on chamber geometry, volume, and analyzer response time, and are therefore described as practical considerations rather than as a single universal protocol.

Comments 4: Provide a complete QC/QA workflow: explicit flags (leaks, poor mixing, curvature), thresholds, and handling rules; include a flowchart or checklist.

Response 4: In the revised manuscript, we clarify practical aspects related to sensor warm-up, periodic replacement of electrochemical sensors when applicable, cross-sensitivity issues for certain gas sensors, and logging of relevant parameters. These elements are discussed in the sensor configuration section. A fully prescriptive QA/QC workflow is not imposed, as SAGE is designed as a flexible platform compatible with different analyzers and deployment conditions.

Comments 5: Make the Li-COR comparison a real validation: report N (paired cycles), number of days/sites, surfaces (soil/water), environmental ranges; ensure identical fitting/QC rules.

Response 5: We understand the reviewer’s request for clarification. The Li-COR comparison presented in the manuscript is intended as a controlled reference comparison illustrating consistency of flux estimates under comparable geometric conditions. The revised manuscript clarifies the experimental context and the purpose of this comparison, which is to demonstrate operational consistency rather than to provide an exhaustive validation campaign.

Comments 6: Report proper agreement statistics: bias, RMSE/MAE, confidence intervals; add an agreement analysis (e.g., Bland–Altman). A single scatter plot is not validation.

Response 6: We acknowledge the reviewer’s suggestion regarding agreement statistics. The current manuscript presents representative datasets and flux comparisons to illustrate consistency between systems. A full statistical validation campaign would exceed the scope of this platform-oriented manuscript; however, the comparison provided supports the practical robustness of the SAGE platform.

Comments 7: Show time-series overlays: at least one representative cycle where SAGE and Li-COR concentration curves and derived flux are compared under identical closure timing.

Response 7 We clarify that the comparison between SAGE and the reference chamber is performed at the flux level. Raw concentration time series may differ due to tubing volume, internal configuration, and analyzer response characteristics. The manuscript now clarifies this point to avoid ambiguity.

Comments 8: Metrology for each quantitative channel (minimum CO₂ and O₂): calibration procedure/traceability, response time (t90), noise/precision, drift, RH/T dependence, and cross-sensitivity

Response 8: The manuscript clarifies that the embedded CO₂ and O₂ sensors used in our deployments have been characterized in our previous peer-reviewed work, which is explicitly referenced. The revised text also clarifies the intended use of the different gas channels (quantitative versus indicative), as well as practical considerations such as sensor replacement and cross-sensitivities where relevant.

Comments 9: If CH₄/NH₃/H₂S channels are kept: clearly state whether they are quantitative or only indicative detectors; provide interference/cross-sensitivity testing (RH, sulfur poisoning, etc.) and remove unsupported quantitative claims.

Response 9: We have clarified in the manuscript that NH₃ and H₂S channels are used primarily as indicative detectors rather than as fully quantitative sensors. We also explicitly mention known cross-sensitivity issues for CH₄ MOX sensors and explain that this channel was not retained for quantitative applications in our configuration.

Comments 10: Provide a full flux uncertainty budget: propagate uncertainties from dC/dt (fit + noise + drift), V and S, T/P corrections, timing, mixing delay, leaks/venting; report flux with confidence intervals.

Response 10: The revised manuscript includes a structured discussion of the main sources of uncertainty affecting chamber-based flux measurements, including flux stability, analyzer performance, chamber volume estimation, leakage, and installation conditions. These elements are presented qualitatively, as their quantitative contribution depends strongly on the selected analyzer and field setup.

Comments 11: Quantify leak rate and pressure equilibration: provide a measured leak rate (pressure decay or tracer test) and show pressure differential control during closure.

Response 11: The manuscript clarifies the pressure-equilibration design of the SAGE chamber (expansion volume approach) and discusses potential leakage sources such as tubing and connectors. Because leakage behavior depends on installation and environmental conditions, a universal leak-rate value cannot be provided. The discussion has been clarified accordingly.

Comments 12: Quantify mixing: demonstrate mixing time constant vs fan speed; show that mixing is fast relative to closure duration; discuss bias if not.

Response 12: We thank the reviewer for raising the important issue of mixing dynamics. In the manuscript, mixing is discussed in relation to chamber geometry, internal fan operation, and installation conditions (e.g., vegetation volume, tubing configuration), which can affect effective chamber volume and air circulation. Because SAGE is designed as a flexible platform adaptable to different volumes and field configurations, a single mixing time constant cannot be defined universally. The manuscript, therefore, presents mixing considerations qualitatively and emphasizes the practical exclusion of initial data points to avoid potential mixing artifacts. We clarify in the revised text that adequate mixing relative to closure duration must be verified in each specific configuration, particularly when vegetation volume modifies effective chamber geometry. These considerations are inherent to closed-chamber methodology and are not specific to the SAGE platform itself.

Comments 13: Quantify transparent chamber heating bias and mitigation: provide data on temperature rise during closure under sun/wind and demonstrate an effective mitigation protocol (not only discussion).

Response 13: We agree that transparent chambers may induce temperature variations due to solar radiation. This limitation applies to all transparent chambers. In the revised manuscript, we clarify this point and describe how SAGE allows implementation of temperature-based termination criteria to mitigate such effects.

Comments 14: Mandatory reproducibility deliverables: deposit raw datasets used for validation figures + analysis code (flux fitting + QC) + metadata (conditions, chamber configuration, sensor versions) with clear versioning/DOI.

Response 14: We acknowledge the reviewer’s request regarding reproducibility materials. The manuscript provides complete hardware documentation (mechanical files, electronic schematics, and PCB files where applicable), which are referenced in the text. These materials ensure the reproducibility of the chamber design itself. The laboratory comparison dataset presented in the manuscript serves as an illustrative validation example. These data are part of ongoing collaborative studies and are therefore not deposited separately at this stage. The flux fitting procedure described in the manuscript follows established closed-chamber methodology, and the analytical approach is explicitly described in the text. Given that SAGE is a platform compatible with different analyzers and configurations, reproducibility primarily concerns hardware transparency and methodological clarity, both of which are addressed in the revised manuscript.