Formaldehyde and Total VOC (TVOC) Commercial Low-Cost Monitoring Devices: From an Evaluation in Controlled Conditions to a Use Case Application in a Real Building

Round 1

Reviewer 1 Report

In their paper, the authors study the combination portable commercial sensors for real time monitoring of Formaldehyde and TVOC. They rise a very interesting point which is: Are commercial gas sensors reliable enough for accurate and long term monitoring of pollutant.

In general, the topic is appealing but many inaccuracies make the paper hard to follow/understand. At this stage, it's still in early draft state and need to be polished in order to give a nice story.

Among the principal inaccuracies, here are the most important in my point of view:

All the links for the reference in the text are broken (this shouldn't even appear!) In the introduction, it would be relevant to quickly explain the work principle of the gas sensor used. For example line 362, what are sensor 1 and 2 (EC? How are they different?). Name it EC1 or EC2, it would be easier to follow. Define also who is the supplier and model of each sensor, it would be useful for the reader. Correct most of the figures: wrong legend, pictures low quality or not relevant Figure 5 doesn't give any information Correct lot of typo in the main text Figure 10 and 11, the graph is cropped

The draft need to be reorganized and corrected in order to give a full feedback and it's doable!

Author Response

dear reviewer, thanks for your feedback on the submitted paper. I did my best to take into accounts your comments.

I made major revision to the article architecture, shortening it a little.

please find below my answers in blue to your requests:

All the links for the reference in the text are broken (this shouldn't even appear!) : I corrected this In the introduction, it would be relevant to quickly explain the work principle of the gas sensor used: I Added a part on the sensor description in the Materials and Method part For example line 362, what are sensor 1 and 2 (EC? How are they different?). Name it EC1 or EC2, it would be easier to follow: I followed your recommendation, naming sensor based on the technology Define also who is the supplier and model of each sensor, it would be useful for the reader: on this particular part, I am afraid I can't answer positively to your request. We Don't want to make an advertisment on any of the commercial devices, to stay neutral. Correct most of the figures: wrong legend, pictures low quality or not relevant Figure 5 doesn't give any information Correct lot of typo in the main text Figure 10 and 11, the graph is cropped : I globallly reviewed the legend and typo throughout the article. I removed picture 5 that you found irrelevant. initially I put it to give an insights on the testing facilities and you can see all the sensors on the trolley. The draft need to be reorganized and corrected in order to give a full feedback and it's doable: I did a major reorganization of the article

Best regards

V. Goletto

Reviewer 2 Report

State the objectives of the work and provide an adequate background, avoiding a detailed literature survey or a summary of the results. I can find the introduction section is too lengthy. Try to rewrite this section again and provide relevant literature. Provide a clear motivation for this work. How the author present work gain novelty needs to be clearly addressed in the script. The research article looks more like a review article. Results and discussion are too lengthy and confusing. The author need to shorten the write-up. And provide the salient finding under results and discussion. A total of 14 references are provided in this script. I think the author has not done the literature survey much. More references related to this work need to be incorporated in this script. Many places I can find a few sentences are very confusing. I may advise the author to go through the script thoroughly and try to make amendments in the presentation of this work and also languages need to be corrected properly. What is the future prospect of the present work that needs to be highlighted under the conclusion section?

Author Response

Dear Reviewer, thanks for taking the time to review the submitted paper. I did a major revision of the text, doing my best to take into account your requests.

please find below in blue my answer to each of your suggestions

State the objectives of the work and provide an adequate background, avoiding a detailed literature survey or a summary of the results. I can find the introduction section is too lengthy. Try to rewrite this section again and provide relevant literature. Provide a clear motivation for this work. How the author present work gain novelty needs to be clearly addressed in the script. The research article looks more like a review article. Results and discussion are too lengthy and confusing. The author need to shorten the write-up. And provide the salient finding under results and discussion: I did revise the full article organization, shortening it. A total of 14 references are provided in this script. I think the author has not done the literature survey much. More references related to this work need to be incorporated in this script: I did add some relevant references to the paper, the difficulties for me was to find papers that were presenting sensor evaluation of commercial devices and not papers presenting evaluation of sensor samples prepared at lab scale, still at early stage of research, which is out of the scope of the experimentation described. Many places I can find a few sentences are very confusing. I may advise the author to go through the script thoroughly and try to make amendments in the presentation of this work and also languages need to be corrected properly. What is the future prospect of the present work that needs to be highlighted under the conclusion section? : I think the major revision of the article organization will answer to your request

best regards

V. Goletto

Reviewer 3 Report

General comment

The study is interesting, represent a lot of experimental work but the article needs some improvements. I think the article should be accepted, after a revision.

There are faults in numeration of sections and in automatic numeration of tables and figures.

Introduction

The authors list some projects in the area of ambient air, but should list projects in the area of indoor air as for example the MNT-ERA.net project VOC-IDS, that aims to develop of a selective sensor for specific VOCs.

In Table 1 it is not clear which values are presented: guidelines or values normally found indoors? Please clarify and correct it according the selection.

Methods

Figure 6 – photos of rooms d) and e) are missing, or delete them from the legend of figure.

Results

Figure 9 is numerated as Figure 1.

Figure 16 – legend missing for HCOH Visves data

Figure 17 – legend missing for HCOH data

Figure 21 – period of passive sampling is indicated by the arrows?

Line 672 -673 - “as can be seen on Figure 2, temperature is very similar between the rooms during this period” – correct the number of the figure to 21.

Discussion

The authors do not refers if the TVOC sensors are sensible to VVOC. From my experience, some PID sensors are sensible to ethanol and acetone, which are compounds that are not included in TVOC calculation by reference method. Perhaps is an information that should be taking in account in the discussion of results obtained.

References

I think the list of references is short, and there are some lacks:

The reference of ISO 16000-29 is incomplete.

The references to ISO 16000-3 and ISO 16000-6 should be added, as are the reference methods for formaldehyde and TVOC calculation

Reference 11 is incomplete

Author Response

Dear Reviewer,

thanks for taking the time to provide feedback on the submitted article. I did a major revision of the manuscript, I did my best to take into account your requests.

Please find below in blue my detailled answer to your suggestions:

There are faults in numeration of sections and in automatic numeration of tables and figures : this was revised and corrected

Introduction

The authors list some projects in the area of ambient air, but should list projects in the area of indoor air as for example the MNT-ERA.net project VOC-IDS, that aims to develop of a selective sensor for specific VOCs.

In Table 1 it is not clear which values are presented: guidelines or values normally found indoors? Please clarify and correct it according the selection.

--> I Added bibliographic reference including consortium projects such as the one you are mentionning. I clarified the references from which figures shown in Table 1 were extracted;

Methods

Figure 6 – photos of rooms d) and e) are missing, or delete them from the legend of figure.

--> I decided to put the pictures in a supplementary information, I checked that the legend is correctly displayed

Results

Figure 9 is numerated as Figure 1.

Figure 16 – legend missing for HCOH Visves data

Figure 17 – legend missing for HCOH data

Figure 21 – period of passive sampling is indicated by the arrows?

Line 672 -673 - “as can be seen on Figure 2, temperature is very similar between the rooms during this period” – correct the number of the figure to 21.

--> I did the corrections requested

Discussion

The authors do not refers if the TVOC sensors are sensible to VVOC. From my experience, some PID sensors are sensible to ethanol and acetone, which are compounds that are not included in TVOC calculation by reference method. Perhaps is an information that should be taking in account in the discussion of results obtained.

--> It is topic we have not looked at during the trials. we didn't get any information from the sensor provider about that.

 References

I think the list of references is short, and there are some lacks:

The reference of ISO 16000-29 is incomplete.

The references to ISO 16000-3 and ISO 16000-6 should be added, as are the reference methods for formaldehyde and TVOC calculation

Reference 11 is incomplete

I corrected the reference list, adding some more publications and standards that I Fould relevant in the context of the study.

Best regards.

V.Goletto

Round 2

Reviewer 1 Report

The authors have improved the contents of the paper that start to be readable. Nevertheless many inaccuracies remain and some explanations are rather confusing.

First of all, a special care of the writing and spell check need to be considered. Avoid small sentences and insert linking words to give a pathway of the delivered information. Notably, avoid sentences that do not give information to the reader.

The introduction gives a much better understanding of the working principles of the sensors used but the information of TVOC (definition and name of the chemicals) has disappeared. Also we need to know where those pollutants comes from specially in indoor.

Explanation of reference sensors should be added in the "sensors and sensing technology" part.

In section 3.1.3, it is not clear why there are peaks of formaldehyde concentration. In figure 10, specify the meaning of the arrows directly in the legend.

Check all the graphs and keep the same format (font, units) and denomination.

For the 3.2 part, where the TVOC comes from to do the measurement? Is there an evaluation at the lab scale? In figure 15, which concentration of TVOC has been used to establish the sensor scaling factor (put the entire name in the graph, not just "scaling" which is inaccurate). Use subscript and superscript to write the formulas.

Avoid statements like "quite good" which is not relevant. Please have a look on this website : https://www.scribbr.com/academic-writing/taboo-words/

Figure 16 and 17, there are different sensor responses for the same TVOC concentration and sensor (at 50 ug/m3). The graphs have to be labelled in the same way. Furthermore microg/m3 is not a good unit format (ug/m3 is commonly used).

In part 3.3, the humidity impact is one of the most important parameter to evaluate and there is not enough data on it. It is a pity.

Author Response

Dear reviewer, please find below a point by point response to your comments

The authors have improved the contents of the paper that start to be readable. Nevertheless many inaccuracies remain and some explanations are rather confusing.

First of all, a special care of the writing and spell check need to be considered. Avoid small sentences and insert linking words to give a pathway of the delivered information. Notably, avoid sentences that do not give information to the reader.

I revised the English wording and spelling; English is not my mother language, I could go through English editing provided by the editor if I can have additional delay for them to provide feedback.

The introduction gives a much better understanding of the working principles of the sensors used but the information of TVOC (definition and name of the chemicals) has disappeared. Also we need to know where those pollutants comes from specially in indoor.

I added some definitions and information on TVOC main indoor sources in the introduction

Explanation of reference sensors should be added in the "sensors and sensing technology" part.

I didn’t understand what is needed for this particular point

In section 3.1.3, it is not clear why there are peaks of formaldehyde concentration.

I make an assumption in the text regarding appearance of formaldehyde spikes.

In figure 10, specify the meaning of the arrows directly in the legend.

Check all the graphs and keep the same format (font, units) and denomination.

graphs were checked (legend, denomination…)

For the 3.2 part, where the TVOC comes from to do the measurement?

Additional information is provided in the text; detailed list and concentrations of VOCs is provided as Supplementary materials.

Is there an evaluation at the lab scale? In figure 15, which concentration of TVOC has been used to establish the sensor scaling factor (put the entire name in the graph, not just "scaling" which is inaccurate). Use subscript and superscript to write the formulas.

Requested Information is provided in the article.

Avoid statements like "quite good" which is not relevant. Please have a look on this website : https://www.scribbr.com/academic-writing/taboo-words/

Figure 16 and 17, there are different sensor responses for the same TVOC concentration and sensor (at 50 ug/m3). The graphs have to be labelled in the same way. Furthermore microg/m3 is not a good unit format (ug/m3 is commonly used).

Correction has been done.

In part 3.3, the humidity impact is one of the most important parameter to evaluate and there is not enough data on it. It is a pity.

As we did not have enough data points on humidity impact, it was deliberately not described here. But this is something we are looking at, as some of our applications are in hot and humid climate. we know it has however a huge impact on sensors

Reviewer 2 Report

Minor English editing required.

Author Response

dear reviewer:

I did some amendment to the content based on your recommendations

I did correct the English wording

English is not my mother language, I could use the English Edition option of the website if I can be given additional delay to have it reviewed.

Regards

Round 3

Reviewer 1 Report

I appreciate the corrections provided by the authors.

I definitely suggest to the Authors to request external help for the English writing. I understand that it is not the mother tong of the Author like many many scientists. Nevertheless, it does not justify the quality of the writing. So please, review carefully the writing avoiding short sentences, repetitions, and sentences that do not give relevant information.

The way how data are shown in Figures 16 and 17 is rather confusing. If you do 2 measurements at 60 ug/m3 then you should implement an error bar instead of using 2 points for the Ssensor at the same concentration. Furthermore, there are no explanations on this difference (that is important).

The paper should be ready to be published after these modifications.

Author Response

Dear reviewer, thanks again for your time reviewing the paper.

please find below my answers

I appreciate the corrections provided by the authors.

I definitely suggest to the Authors to request external help for the English writing. I understand that it is not the mother tong of the Author like many many scientists. Nevertheless, it does not justify the quality of the writing. So please, review carefully the writing avoiding short sentences, repetitions, and sentences that do not give relevant information.

The article was submitting to the MDPI english editing service.

The way how data are shown in Figures 16 and 17 is rather confusing. If you do 2 measurements at 60 ug/m3 then you should implement an error bar instead of using 2 points for the Ssensor at the same concentration. Furthermore, there are no explanations on this difference (that is important).

Figures 16 and 17 have been modified and explanations have been provided in the text.

Regards

Valérie Goletto

Round 4

Reviewer 1 Report

The manuscripted is now ready for publication