The manuscript describes the results of a large blind controlled methane release experiment. It presents the results of eight commercial quantification techniques that were assessed over an intensive 4 week release campaign, where emission rates were varied over several orders of magnitude in 45 min blocks (including zero release periods). The experiment is well described with considerable additional technical details provided in the supplementary information. The discussion and conclusions are thoughtfully considered and well presented.

The study found good methane detection amongst the various techniques but poor quantification across all techniques employed, with a surprising high number of false positives in some cases. Even with a wide 50-150% confidence internal around the true release value, most techniques achieved this less than 40% of the time. The generally poor quantification performance is concerning but consistent with similar release studies. As noted by the authors, the experimental design exacerbated the poor performance by forcing participants to report quantification results under non-optimal wind and other environmental conditions. Nevertheless, the study highlights the need to develop better methodologies for quantification, particularly for measuring and describing wind speed and variability. Short release periods disadvantage fixed sensors as the wind direction and speed may not be optimal for measurements, highlighting the advantage of mobile and scanning systems. The study provides further evidence of the mismatch between the aspirations of regulators to accurately quantify methane emissions and what is possible using current technologies and quantification methodologies.

Specific comments

Ln 11, Remove all reference to academic in this paper. The study tested commercial techniques and the quantification codes are not provided in the manuscript or supplementary information. I understand the results from academic teams will be presented in an accompanying paper. I’m not sure “public” adds much – it what way?

Ln 12, This not the first blind methane detection and quantification study in Europe. Please refer to Liu et al (2024) AMT 17, 1633–1649, 2024.

Ln 27, …have contributed

Ln 28, …pre-industrial time, and given …

Ln 34, U.S. Inflation Reduction Act – I’m not sure this is a relevant example anymore given recent developments.

Ln 63, remove academic.

Ln 140,  Table 2 can be moved to the supplementary information. Not contributing much for the reader here.

Ln 158, Table 3 delete columns 2-5 and replace with a single column with the number of estimate submissions. Data is repeated in a different form in columns 6-9.

Ln 180, This figure and its caption are confusing – please remove. Table 3 is a more useful summary of false positives etc.

Ln 219-223 and Table 4. It would be interesting to include a column that shows the “Participant estimates within +/- 10% of the true value” and provide a short discussion. This is the kind of number that regulators have in mind and it would be good to show just how problematic this is. If not 10%, check relevant policy documents to see what recent expectations are.

Ln 340, remove “first public, academic”

Supplementary Information.

P35,  “Names of individual personnel not required”.

P36-43, Remove references.

General comments

Firstly, I would like to apologize for only finding the time to write this comment now. I hope it hasn't caused any unnecessary inconvenience or problems.

The publication “Controlled release testing of commercially available methane emission measurement technologies at the TADI facility” by McManemin et al. addresses the important aspect of evaluating methane detection and quantification technologies in Europe. For this reason, controlled release experiments were conducted at the TADI facility in France in 2024. This publication compares and evaluates the results of eight commercially available technologies. Participants had to submit their estimates without knowing the true emissions. They also had to use their own device to collect the wind data that was essential for making the estimates. Subsequently, true emissions and wind data at the source were released. A key finding was that the prevailing and measured winds were a critical parameter for estimating the emission rate. The findings reinforce the statement that wind speed and direction are just as important as concentration measurements. The manuscript is well within the scope of AMT, and I recommend publication following the implementation of the minor modifications suggested in the comments below.

Specific comments

P5, L95: It might be worthwhile listing the academic teams and their technologies as well, to get a better overview – potentially in the supplement.

Fig. 2: What does the dark blue bar represent in the diagrams? Why is there a split at 50 kg/h? Although, as the other reviewer mentioned, this figure is not easy to grasp at first, it nicely shows the different types of detection (TP, FP, FN) in terms of release rates.

P12, L247: Please define CoV.

P13, L251: What do the authors mean by 'aggregate'? Are they referring to binned winds?

P16, L340f: I could not find any analysis of observations among the eight commercial systems that classify as 'aircraft' or 'vehicle' in this work. Please remove them from the list throughout the text.

P17, L370f: I do not understand why “the study design focused on mobile ground-based solution” although the analyzed technologies were either airborne (or even space-born) or continuous monitoring, at least, in this work. Did the academic teams (not evaluated here) primarily deployed mobile ground-based solutions?

Technical corrections

P5, L94: I could not find SI Section 1.2.2 in the Supplement.

h vs. hr: Please use common units for hour.

Table 4: Shift text below Table to caption or use footnotes.