Sizing Accuracy of Low-Cost Optical Particle Sensors Under Controlled Laboratory Conditions

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The study evaluates the particle sizing capability of low-cost particle sensors. While the methods and results are not entirely novel, the study contributes to the growing body of literature that highlights the primary limitation of these sensors—inaccurate particle sizing. Given the increasing interest in low-cost air quality monitoring, this work remains relevant and valuable.

I have a few minor comments that should help the authors to improve their paper before publication.

• 60-61: For a European audience, it would be worthwhile to mention that the Palas Fidas 200 is also a type-approved instrument that uses an optical detection method. This would provide a broader perspective on reference-grade instrumentation.
• 103-105: Is the SPS30 similar to the PMS5003 in terms of signal processing?
• Results, Figures 2-6: Maybe I missed this but how is the unit %/µm defined? A brief explanation would be useful.
• Section PM2.5/PM1 and PM10/PM2.5 Ratios measured with PMS5003 and SPS30: To me, this section does not appear to contribute much to the overall discussion. I think the authors should re-consider whether this section warrants its own subtitle. Or maybe expand the analysis; is there any hypothesis why, especially for the SPS30, there seems to be a distinct value change between the 0.6 and 1 µm size (from 1.2 to 3.6/1.8)? I'll leave for the authors to decide the best way to better utilize the Table 2 data.
• 304-305: I would perhaps add a notion that the inability to correctly size particles may also be resulting at least partly from the electronic design and used signal processing methods and algorithms. This was already mentioned previously in the manuscript.
• Conclusions: Maybe a noteworthy remark would also be the price difference between the DRX and OPC. At least I was expecting better performance from the more expensive DRX as it is not precisely in the "low-cost" category.

Author Response

Please see the attached Responses to Reviewer 1.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article presents a study of particle sizing accuracy using low-cost PM sensors. In my opinion, the results obtained are relevant in the field of air quality measurements and atmospheric monitoring systems. The research methodology is described in a clear manner, and the obtained results are presented in a readable way. 

I believe that the article should be accepted for publication, with minor corrections:

1) Despite the important subject matter, the presented research methodology is not characterized by special uniqueness. I suggest that the authors describe the novelty of the article at the end of the Introduction, and in the Abstract the importance of the results obtained.

2) Subsection "PM2.5/PM1 and PM10/PM2.5 Ratios measured with PMS5003 and SPS30" - from line 273: I suggest that the reader should be given a more detailed description of what the particle size ratios indicate (what is meant by ratios close to 1 and what is meant by ratios close to 3-4) and how this affects the estimation of concentrations.

3) Figure 2: The descriptions of the OX axis seem to have different sizes, and there is a typo in figure (b) and (c) - “Geomtric” instead of “Geometric”.

Author Response

Please see the attached Responses to Reviewer 2.

Author Response File: Author Response.pdf