I congratulate the authors on the remarkable engineering work carried out, close to a commercial product including many user-friendly functions that make the system almost plug-and-play. Before publishing, I suggest clarifying the following

About calibration and validation

• In section 2.1, you mention the possibility to continuously refine and update the total flux equation as calibration data changes over time while, in section 2.4, you describe one-time calibration (2-point for N₂O, 1-point for CH₄, and factory pre-calibration for CO₂ sensors). This calibration-update feature seems very useful, but if only one-time calibration is needed, which is its purpose?

• More information on how humidity was controlled during the validation measurements and why the chosen RH and temperature, and CO₂, CH₄, and N₂O concentrations are relevant for the later field measurements would be scientifically valuable and increase future usability of Pondi.

About interferences, accuracy, and system validation

• The commercial gas sensors used present interferences. While some of these cross-sensitivities are addressed, others remain. In this sense, it would be very interesting for future uses of Pondi to know certain system specifications. The error linked to temperature and humidity, together with the quantified error via MAPE, represents a measurement inaccuracy, different for each sensor and measurement range. Could you clarify the accuracy of Pondi for each sensor and concentration/measurement range? Is it possible to provide MAPE values for the field measurement range?

• Section 2.6 provides interesting and important insights, but a relevant question might obfuscate them. Was the CO₂ sensor tested against interferences? If CO₂ sensor does not present interferences, the CO₂ contribution from the NO₂ signal can be compensated but otherwise the issue becomes more complex.

• The field measurements and observations are relevant to validating Pondi, while missing data may induce thoughts of hidden information. To remove this residual possibility, could you include temperature and humidity data in Figures 6, 7, and 8? Do you have long-term terrestrial flux measurements including the different used sensors? Did you notice long-term drift in any of the sensors used? Could saturation values vary over time as seems to happen in Figure 6 and 7?

The article by Malerba and others present a new chamber to measure GHG fluxes from ecosystems, in a very refined design, with telemetry, being one of the most advanced chambers available. The authors also test and present key details on the performance of the equipment, even though some details are missing that I list below.

The only bigger issue I have is a bit more details on the items and estimated cost of a Pondi. Other studies presenting similar chambers (e.g. So et al, 2024; reference below), do a great job with a table of all the main items, sources and rough cost. This would allow a better comparison to other chambers available as well as commercial options, given that the study highlights "low cost" in several places. The same paper provides a repository with more detailed documentation, which could also be necessary to do for this technical note.

Finally, the paper mentioned above, are able to separate diffusive from ebullitive fluxes of methane, which is something this study could also explore. Maybe no need to do a new analysis, but mentioning this capacity could be relevant.

L50: The first paragraph on the different gasses is too broad on the global sources, it could already be narrowed down to the key ecosystems that this study targets. Particularly relevant would be for methane, as half of global emissions are from aquatic ecosystems (Global Methane Budget, Saunois et al 2025, ESSD). The "UN Environment programme, 2023" has a type and is maybe not the best reference.

L74: If spelling out companies like this, would it be needed to provide references for them?

L93: A key reference missing here would be So et al, 2024

L198: Some details on the external unit with the air pump are missing: What is the specific design here, which type of fan?

L426: Cannot see arrows in the figure, which are mentioned in the caption.

Reference cited: 

Sø, J. S., Sand‐Jensen, K., & Kragh, T. (2024). Self‐made equipment for automatic methane diffusion and ebullition measurements from aquatic environments. Journal of Geophysical Research: Biogeosciences, 129(6), e2024JG008035