Smart Wireless CO2 Sensor Node for IoT Based Strategic Monitoring Tool of The Risk of The Indoor SARS-CoV-2 Airborne Transmission
Round 1
Reviewer 1 Report
Dear authors,
Your paper is interesting and the topic presented follows current trends. The article is well written in a clear way. Furthermore, not much editing is required.
The research and its design are clear and no significant errors were detected. The methods used were described in detail with minor elements to be specified more clearly.
However, some additional corrections must be done for the article to be published as professional scientific work.
1. The abstract gives a good sense of the article and allows even a person not familiar with the field to follow. However, the abstract should not give specific data or values. Additionally, the problem of the abstract is the lack of explanation of the paper's novelty.
2. The authors are referencing mostly new publications, which is the advantage of state-of-the-art analysis. However, some statements are not supported by a literature review, e.g:
• Sentence lines 48-49 reference required
• Line 80-81, reference required e.g Lukasz Scislo, Air Quality Sensor Data Collection and Analytics With IoT for an Apartment With Mechanical Ventilation.
• Additionally, one element which is missing from state-of0the art analysis is the connection the IoT network used for e.g controlling ventilation with space occupancy or occupants' schedules which is interesting in the scope of usage for limiting the spread of Covid. The reference from the previous point can be also used for this.
Otherwise, the introduction is very well structured. The only problem is the last paragraph with the aim and the scope of the research where again the novelty of the proposed study is not explained strongly enough.
3. Fig. 2 has some problems with figure orientation and visibility probably due to the way the pdf was created. It is advised to improve the quality.
4. The materials and methods chapter is explained in detail and no changes are required at this point.
5. Fig.8 is not readable suggesting enlarging. It also looks that hight to width scale is wrong.
6. Fig.9 right photo it also looks that hight to width scale is wrong
7. Fig.12 similar problem and also suggests enlarging.
8. Fig.14 the values on graphs 7 and 25 (ms) are suggesting that those values are in seconds. Please, make the indication of the unit. Additionally, the graph Y axis is said to be in ms but the values of transmitting and sleep are in second. This graph needs to be changed so It shows the values in the correct units (in table 6 it is correctly shown).
9. Fig. 16 is out of focus and maybe the width-to-height scale not correct. Also, this graph looks basic. Suggest improving the quality.
10. Fig. 18 again high to wdth scale wrong. No information is visible. Suggest enlarging and putting both screens in one column, not in one row.
11. Fig.9 suggest seeing if maybe it is better to show it as a different type of plot so values for both measurements are always visible.
12. Otherwise, the discussion of the results is good.
Conclusions:
The topic of the article is interesting and the article has no significant problems with methodology. However, this is mostly an introduction to the design and implementation of engineering solutions with a statement of novelty. The article requires some improvements and in its current form, the authors are asked for some revisions. Although there are no significant problems with methodology due to problems with the presentation of the results the reviewer asks for major improvements in this area. Otherwise many of the figures/graphs look more like taken from a student thesis than a professional presentation required in a scientific article.
Author Response
Dear Reviewer_1
Thank you very much for your kind comments and suggestions regarding the content of our manuscript. The revisions of our manuscript are discussed in the attachment.
The text in the manuscript was reviewed by Native English Editing Service.
Please see the attachment
Regards
The authors
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The article is well-written and describes the development of an IoT sensor node for CO2 measurement. The authors use CO2 as an indirect measurement of indoor Sars-CoV-2 airborne risk of transmission because there is a close correlation between CO2 and the presence of aerosol particles.
* This paragraph is confusing and redundant:
"The node is composed of a Non-Dispersive Infrared (NDIR)-based CO2 sensor for CO2 sensing, a Sensorion Humidity Temperature (SHT)75 sensor for temperature and humidity sensing, an ATmega 128L as a processor, a Chipcon CC2420 as a wireless communication modem, and 12 V external power supply. The sensor node was applied in a real subway station using a Wireless Sensor Network (WSN) system, with the measuring error rate of the CO2 sensor being ± 30 ppm. A sensor node was developed and equipped with multiple sensors, CO2, temperature, humidity, and VOC, to monitor indoor air quality [24]. The node consists of an Arduino Uno microcontroller board, MG811 CO2 sensor, TGS2602 VOC sensor, and RTH03 digital temperature and humidity sensor."
* The paragraphs in the Introduction are too large, which makes the text difficult to understand.
* The possible future system node integration to a micro energy harvester element description should be in the conclusion section.
* The subsections 2.3.2 and 2.3.3 have the same name, i.e., "Hardware design."
* The letters in Figure 8 are too small to read.
* The authors should move the sensor calibration process to the Material and Methods Section.
* In a Pizza Graph is impossible to see the participation of Initializing and CO2 Reading in the disc.
* The authors need to clarify the use of the cloud service, e.g. if they paid some services billing.
Author Response
Dear Reviewer_2
Thank you very much for your kind comments and suggestions regarding the content of our manuscript. The revisions of our manuscript are discussed in the attachment.
The text in the manuscript was reviewed by Native English Editing Service.
Please see the attachment
Regards
The authors
Author Response File: Author Response.pdf
Reviewer 3 Report
This paper presents a smart wireless sensor node that can measure and monitor indoor CO2 concentration levels over time, which has a certain practical value. It's easy to read for readers to understand, but there are a few problems.
The description of the hardware composition should be appropriately reduced, focusing on the measurement results and error analysis.
Check the analysis of the paper to make it more logical and optimize the expression of the summary and conclusion.
Check the English language in the manuscript with special attention on the tense and word order of the manuscript.
After making changes to the manuscript, I recommend publishing it.
Author Response
Dear Reviewer_3
Thank you very much for your kind comments and suggestions regarding the content of our manuscript. The revisions of our manuscript are discussed in the attachment.
The text in the manuscript was reviewed by Native English Editing Service.
Please see the attachment
Regards
The authors
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Dear authors,
The article was improved according to the points from the 1st review
Although the quality of the paper still can be improved, if no additional requests are asked by the other reviewer/s, the paper can be accepted for publication.
