Evaluating Emissions from Select Urban Parking Garages in Cincinnati, OH, Using Portable Sensors and Their Potentials for Sustainability Improvement

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Study "Evaluating Emissions in Urban Parking Garages Using Portable Sensors and its Potential Integration into Smart Parking Systems" includes air quality measurements in three parking garages in Cincinnati with low cost sensors. The main focus is on PM2.5 concentrations but other pollutants are also included. The results from these garages is compared to a urban air quality station monitoring pollutants levels in the local urban environment.

The current version of the submission seems to be done in haste and is incomplete:

• results presented in the supplementary material; I cannot find this material at all.
• reference at row 481 is not stated
• sentence at row 482 cuts in the middle
• refence at row 549 is not complete
• typos here and there
• messy Fig. 3

One major concern is that PM2.5 and PM10 are not sensitive to the traffic volume in the garages since traffic aerosols are small in size. This is quite well known in the literature and comes as no surprise. Some other metric like ultrafine particle number or LDSA would be better for the analysis of car emission impacts inside the garages. The current novelty value of the manuscript is very low. 

On the positive side the long measurement time window and the measurements locations are impressive, and in principle would enable creation of scientific value. Since there are grounds for a better manuscript, authors should focus on finding novelty in the available data set with more extensive analysis while also creating a more coherent manuscript. Hence, I would recommend rejection/major revision of the current submission.

Author Response

Study "Evaluating Emissions in Urban Parking Garages Using Portable Sensors and its Potential Integration into Smart Parking Systems" includes air quality measurements in three parking garages in Cincinnati with low cost sensors. The main focus is on PM2.5 concentrations but other pollutants are also included. The results from these garages is compared to a urban air quality station monitoring pollutants levels in the local urban environment.

The current version of the submission seems to be done in haste and is incomplete:

• results presented in the supplementary material; I cannot find this material at all.  
• reference at row 481 is not stated
• sentence at row 482 cuts in the middle
• refence at row 549 is not complete
• typos here and there
• messy Fig. 3

R: We are sorry for  the editorial oversights. The discussion in Row 481 and 482 has been updated. We had two versions  of the paper, and inadvertently pasted the incomplete one.  The editor suggested that supplementary material (also updated) can be submitted to him/her, so as to make sure the reviewers can see it.  The rest has all been fixed.

One major concern is that PM2.5 and PM10 are not sensitive to the traffic volume in the garages since traffic aerosols are small in size. This is quite well known in the literature and comes as no surprise. Some other metric like ultrafine particle number or LDSA would be better for the analysis of car emission impacts inside the garages. The current novelty value of the manuscript is very low. 

R: We are appreciative of the suggestion on ultrafine particles (UFP) and did both a literature search and data analysis. We only had two instances of UFP measurements, since the instrument available was not very portable (p-trak by TSI). The results were added to the “Limitations” session, as this warrants more future work.

On the positive side the long measurement time window and the measurements locations are impressive, and in principle would enable creation of scientific value. Since there are grounds for a better manuscript, authors should focus on finding novelty in the available data set with more extensive analysis while also creating a more coherent manuscript. Hence, I would recommend rejection/major revision of the current submission.

R:  We added more discussion to data analysis, revised the following sections: the abstract, conclusion, and limitation discussion.

Reviewer 2 Report

Comments and Suggestions for Authors

Overall, the manuscript is ok. However, several areas require improvement to ensure clarity, consistency:

Areas for Improvement

1. Language and Formatting

   • Please check for typographical errors and ensure formatting consistency throughout the manuscript.

   • Some text remains highlighted in red (e.g., line 346), suggesting incomplete revisions.

   • Section 6, Limitations, appears to be unfinished (see line 482); this section must be fully developed before submission.

2. Figures and Visual Clarity

   • The quality of the illustrations needs significant enhancement. For instance, Figure 3 is blurry, and text within Figure 5 is difficult to read. Please provide high-resolution images and ensure legibility of any embedded text.

3. Scientific Content

   • The paragraph from lines 199 to 207 does not clearly contribute to the main objectives of the paper. Please clarify its relevance or consider its removal.

   • The uncertainty analysis for the measuring devices is not sufficiently addressed. This is a critical component of the study and should be thoroughly described and justified.

   • The abstract is currently too general. Consider rewriting it to clearly summarize key results, methodologies, and conclusions.

   • Some sections of the manuscript do not align with the core focus of the study. Please revise to ensure all content supports the research objectives.

 

Author Response

Overall, the manuscript is ok. However, several areas require improvement to ensure clarity, consistency:

Areas for Improvement

1. Language and Formatting
   • Please check for typographical errors and ensure formatting consistency throughout the manuscript.
   • Some text remains highlighted in red (e.g., line 346), suggesting incomplete revisions.
   • Section 6, Limitations, appears to be unfinished (see line 482); this section must be fully developed before submission.

R: We checked for typos, and highlight of L346 was fixed. The discussion in Line 481 and 482 has been updated. We had two versions  of the paper, and inadvertently pasted the incomplete one.

2. Figures and Visual Clarity
   • The quality of the illustrations needs significant enhancement. For instance, Figure 3 is blurry, and text within Figure 5 is difficult to read. Please provide high-resolution images and ensure legibility of any embedded text.

R: Figures 3 and 5 were redrawn for clarity.

3. Scientific Content
   • The paragraph from lines 199 to 207 does not clearly contribute to the main objectives of the paper. Please clarify its relevance or consider its removal.

R: Lines 199 to 207 discussed the sustainability aspects of UC garages (which is very limited). This was suggested by the editor (for better fit with the journal theme) when we submitted the initial paper proposal. Although it was more work to assimilate this content into the paper, we now think it helps to elevate the paper with future perspectives, as air quality sensors should be considered with smart garage initiatives.  

• The uncertainty analysis for the measuring devices is not sufficiently addressed. This is a critical component of the study and should be thoroughly described and justified.

R: Details of the R-square values from south-coast sensor lab were added to the limitation section. We are aware of the uncertainty these low cost sensors, and hope the long term measurement can help produce a relative trend and reduce the  uncertainty.

• The abstract is currently too general. Consider rewriting it to clearly summarize key results, methodologies, and conclusions.
• Some sections of the manuscript do not align with the core focus of the study. Please revise to ensure all content supports the research objectives.

R: The abstract has been re-written, as well as the discussion, conclusion and limitation section.

Reviewer 3 Report

Comments and Suggestions for Authors

This study by University of Cincinnati presents an evaluation of emissions in urban parking garages by portable chemical sensors for air quality monitoring of some pollutants such as PM, CO2, CO, NO2, VOCs. The results confirmed the highest level of pollution in "close" environments such as garages compared to outdoor pollution. The results are very interesting. The manuscript is well structured. The research is worth of publication. Some Minor Revisions are suggested:

1. A table reporting the technical data of used sensors such as datasheet should be added.
2. Time-series of sensors used during experimental campaign should be added to appreciate the data of study
3. At page 6 is cited the co-location of sensors and reerence analyzers as well-known technique to assess sensing performance. However, co-location is a few meters and not miles/km. Please, comment on this aspect in the text.
4. Additional references should be given in the bibliography.

Author Response

This study by University of Cincinnati presents an evaluation of emissions in urban parking garages by portable chemical sensors for air quality monitoring of some pollutants such as PM, CO2, CO, NO2, VOCs. The results confirmed the highest level of pollution in "close" environments such as garages compared to outdoor pollution. The results are very interesting. The manuscript is well structured. The research is worth of publication. Some Minor Revisions are suggested:

1. A table reporting the technical data of used sensors such as datasheet should be added.

R: A table was added to the supplemental materials.

2. Time-series of sensors used during experimental campaign should be added to appreciate the data of study

R: Time-series of sensors based on the high emission days of Tab. 4 were plotted and added to the supplemental materials.

Also, more sampling details were added, which reads “Measurements were carried out from June 2023 to April 2025, and were randomly selected every month to ensure representatives of the data. A total of 85 measurements were taken at the Campus Green garage, 45 at CCM, and 34 at the Washington Park garage.”

3. At page 6 is cited the co-location of sensors and reerence analyzers as well-known technique to assess sensing performance. However, co-location is a few meters and not miles/km. Please, comment on this aspect in the text.

R: The Taft site was NOT used for side-by-side c-location of sensors. We also clarified this in the manuscript that the concentrations at Taft serves as ambient conditions to compare with the garages.

4. Additional references should be given in the bibliography.

R: 3 articles on UFP were added to the text and the reference section.

Reviewer 4 Report

Comments and Suggestions for Authors

In this manuscript, the authors reported a method for evaluating the emissions of urban parking lots using portable sensors. While the topic is of interest to the target audience, the paper lacks innovative sensor system design and clear application needs. Moreover, some of the conclusions are unsubstantiated. Therefore, I recommend a serious major revision before consideration.  Specific comments are as follows:
1. The introduction is logically disorganized and should be more concise to highlight the core of the research.
2. The introduction should include more references to support the authors' non-original arguments.
3. The manuscript frequently mentions poor air quality due to inadequate ventilation systems. Is this issue absent in areas with better ventilation systems? How should the ventilation system interact with the sensor system mentioned in the paper?
4. The manuscript does not provide details on the practical testing procedures, including sensor calibration and the construction of the testing platform. The related data lacks persuasiveness.
5. The article repeatedly mentions the impact of humidity on measurement results, but real-time monitoring of humidity is lacking from the study, rendering the conclusions unconvincing.

Author Response

In this manuscript, the authors reported a method for evaluating the emissions of urban parking lots using portable sensors. While the topic is of interest to the target audience, the paper lacks innovative sensor system design and clear application needs. Moreover, some of the conclusions are unsubstantiated. Therefore, I recommend a serious major revision before consideration.  Specific comments are as follows:

1. The introduction is logically disorganized and should be more concise to highlight the core of the research.

R: The introduction has been significantly revised taking the reviewer’s recommendation on logical connection. The sustainability related description in the Introduction and Methods  was suggested by the editor (for better fit with the journal theme) when we submitted the initial paper proposal.

2. The introduction should include more references to support the authors' non-original arguments.
   R: 3 articles on UFP were added to the text and the reference section.
3. The manuscript frequently mentions poor air quality due to inadequate ventilation systems. Is this issue absent in areas with better ventilation systems? How should the ventilation system interact with the sensor system mentioned in the paper?
   R: At the reviewer’s suggestion we found many uses of “ventilation” in the text. But these are mainly in citing the literature of  other people’s work, and in garage description. We went to cited literature and noticed a similar phenomenon: ventilation is mentioned but not studied. Ventilation data is not available to our study, and we did not draw any conclusions related to ventilation.
4. The manuscript does not provide details on the practical testing procedures, including sensor calibration and the construction of the testing platform. The related data lacks persuasiveness.
   R: Details on sensors, garages, and measurements are provided in section 2. Also, more sampling details were added, which reads “Measurements were carried out from June 2023 to April 2025, and were randomly selected every month to ensure representatives of the data. A total of 85 measurements were taken at the Campus Green garage, 45 at CCM, and 34 at the Washington Park garage.” The limitation section has also been re-written with added details.

5. The article repeatedly mentions the impact of humidity on measurement results, but real-time monitoring of humidity is lacking from the study, rendering the conclusions unconvincing.

R: We agree lacking humidity data is a limitation, and therefore did not draw conclusion related to humidity. “humidity” was only used three times. One is in the introduction of the sensor, which measures RH; the second use is on p11, which states lower RH in the winter (true in the location studied) and the 3^rd time in Limitations.  Temperature and relative humidity measurements are now recorded in the newer version of the Temtop device but not for the older version. Since different versions of the Temtop devices were used in this two-year study, we do not have Temperature and relative humidity data for every measurement.  Otherwise, humidity data could have been used to draw more conclusions.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors should improve the uncertainty analysis of the measurements.

Author Response

The authors should improve the uncertainty analysis of the measurements.

R: We went back to the literature (27-28) and the Temtop manual, and  added more information to its data accuracy in two  sections:  the “Method” and the “limitation”. We also searched the literature again, and added three more references relevant to Temtop. We found that  Temtop has been used as reference sensors in other studies, which is an indirect support for its data quality.

In addition, we also read through the manuscript carefully for  editorial fixes.

Reviewer 4 Report

Comments and Suggestions for Authors

The manuscript has been revised accordingly and is now ready for acceptance.

Author Response

R: We appreciate the reviewer’s comment. We read through the manuscript carefully for editorial fixes, in addition to adding more discussion on Temtop precision and uncertainty.