Simulating the Natural Seasonal Ventilation of a Classroom in Poland Based on Measurements of the CO₂ Concentration

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The methodology applied in this study involves a combination of in-situ measurements and simulation techniques to evaluate indoor air quality (IAQ) in a classroom environment. 

Major Comments

Extended Measurement Period: While the study provides a detailed snapshot of IAQ conditions over specific days, extending the measurement period to include more varied conditions (e.g., different seasons, varying occupancy) could provide a more comprehensive understanding of IAQ fluctuations over time.

Additional Pollutants: The focus on CO2 is important, but including measurements of other pollutants such as particulate matter (PM), volatile organic compounds (VOCs), and bioaerosols could provide a more holistic assessment of IAQ.

 

Impact Assessment: Further investigation into the health and performance impacts on students and teachers due to poor IAQ, perhaps through cognitive performance tests or health surveys, would strengthen the study's implications on public health.

It would be beneficial to broaden the discussion on air quality into the introduction by incorporating findings from other studies, both outdoor such as  by Lolli et al. (2021) and indoor as byBruce et al. (2000)

Lolli, S. (2021). Is the Air Too Polluted for Outdoor Activities? Check by Using Your Photovoltaic System as an Air-Quality Monitoring Device. Sensors, 21, 6342. https://doi.org/10.3390/s21196342

Bruce, Nigel, Rogelio Perez-Padilla, and Rachel Albalak. "Indoor air pollution in developing countries: a major environmental and public health challenge." Bulletin of the World Health organization 78.9 (2000): 1078-1092.

Comments on the Quality of English Language

English is fine, minor editing needed

Author Response

Major Comments

Extended Measurement Period: While the study provides a detailed snapshot of IAQ conditions over specific days, extending the measurement period to include more varied conditions (e.g., different seasons, varying occupancy) could provide a more comprehensive understanding of IAQ fluctuations over time.

 

We were only able to make the emasuremnets in those specific days but the fluctuation was very similiar. In our opinio it was sufficient to validate the model which can be next used to the more comprehensive cases. 

Additional Pollutants: The focus on CO2 is important, but including measurements of other pollutants such as particulate matter (PM), volatile organic compounds (VOCs), and bioaerosols could provide a more holistic assessment of IAQ.

 

Due to the comments of other reviewer we have decided to change/ adjust the title of article. The new one should precise the main points of our analysis. 

New title: Seasonal natural ventilation simulation of the classroom in Poland based on measurements of CO₂ concentration.

Impact Assessment: Further investigation into the health and performance impacts on students and teachers due to poor IAQ, perhaps through cognitive performance tests or health surveys, would strengthen the study's implications on public health.

It would be beneficial to broaden the discussion on air quality into the introduction by incorporating findings from other studies, both outdoor such as  by Lolli et al. (2021) and indoor as byBruce et al. (2000)

Lolli, S. (2021). Is the Air Too Polluted for Outdoor Activities? Check by Using Your Photovoltaic System as an Air-Quality Monitoring Device. Sensors, 21, 6342. https://doi.org/10.3390/s21196342

Bruce, Nigel, Rogelio Perez-Padilla, and Rachel Albalak. "Indoor air pollution in developing countries: a major environmental and public health challenge." Bulletin of the World Health organization 78.9 (2000): 1078-1092.

 

Thank you for the suggestions, both articles refer to the pollutions of the air and their influence of users. In our article we are specifically focused on the CO2. The listed publications will be very valuable in the other articles where we focus on the influence of particulate matter on IAQ.  

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The presented work aims to investigate the indoor air quality (IAQ) of a primary school classroom in Cracow, Poland, based on CO2 concentration levels exhaled by occupants. the authors conclude that the CO2 levels significantly exceeded acceptable standards, signaling poor air quality during usage time. they thought that this problem is connected mainly with the low efficiency of natural ventilation system being used in the classroom. To address this problem, the classroom environment was simulated using the CONTAM software, and the model was validated against the collected measurement data using the conducted measurement data. Then the simulations for the entire heating season in Cracow were conducted and revealed that the IAQ remained consistently poor throughout the period. the findings highlight the persistent problem of inadequate ventilation in the classroom, which can have adverse effects on the health and performance of students and teachers. in general the topic is sounded and can be publish after English polishing 

Comments on the Quality of English Language

English editing is required 

Author Response

Thank you very much for taking the time to review this manuscript. 

Reviewer 3 Report

Comments and Suggestions for Authors

1. the title doesn't get the main content of the study, only that the authors did the modelling.

2. the abstract states that the authors used CO2 as the missing gas to get poor air quality. Is this conclusion accurate. This is because IAQ is calculated and evaluated with a calculated reference standard.

3. the citation of references. [2,3,4,5,6,7] should be [2-7].

4. lines 67-68, missing references.

5. the introduction is too long. It is possible to integrate the current state of the research with the first half of the section. Or the current state of research part becomes section 2 as literature review and summarise it to get the research gap and importance.

6. the literature review section in 1.1, 1.2 and 1.3 should be in summary language rather than mostly descriptive with *** etc.

7. The various criteria in 1.3 should be succinctly presented in tabular form and placed in the results of the study as an evaluation of the results of this study is sufficient. A detailed interpretation is not required.

8. 2.2 should not appear in Methods, but Results.

9. lines 352-360 should explain the reasons for the fluctuations in CO2 concentration and why CO2 dropped but did not drop below 1000 ppm.

10. lines 367-369, the authors state that 31 people would cause high CO2 concentrations, during which the windows were kept closed? Also, in schools in China, the average number of people in a classroom is 50 or more. Some studies on China, the results obtained are generally consistent with the results of this study.

11. In the modelling section, the geometric dimensions, source settings, detailed methods (e.g. turbulence modelling, wall conditions, etc.), boundary conditions (entrance and exit settings), etc. are not represented. In short, the modelling methods section is not described in sufficient detail. Also, it is recommended to provide 3D modelling diagrams.

12. Why don't I see a cloud view of the pollutant distribution after the simulation? Is it because the simulation software used is different from CFD? Because I have not used this software.

13. Figures 5 and 6 are not described in the text. Model validation should be the result.

14. lines 439-446, missing references.

15. the font of the image is too small, please adjust it.

16. The authors simulated the CO2 pollution level in the classroom in winter. I would like to know what important results the authors got from the simulation. Because the author's simulation study is achievable through real measurements. Therefore, I don't think the simulation alone is significant.

17. Please check the references. Please use literature from the last five years and check the citation format, e.g., missing volume and page numbers, and other issues.

18. Is it permissible to submit a check report with a result of 43%?

Comments on the Quality of English Language

No.

Author Response

1. the title doesn't get the main content of the study, only that the authors did the modelling.

We agree with this comment and we would suggest to adjust the title as follows:

Seasonal natural ventilation simulation of the classroom in Poland based on measurements of CO₂ concentration.

2. the abstract states that the authors used CO2 as the missing gas to get poor air quality. Is this conclusion accurate. This is because IAQ is calculated and evaluated with a calculated reference standard.

We would like to ask for more precise comment. It’s not clear for us.

3. the citation of references. [2,3,4,5,6,7] should be [2-7].

Corrected. 

4. lines 67-68, missing references.

Reference [8]

5. the introduction is too long. It is possible to integrate the current state of the research with the first half of the section. Or the current state of research part becomes section 2 as literature review and summarise it to get the research gap and importance.

6. the literature review section in 1.1, 1.2 and 1.3 should be in summary language rather than mostly descriptive with *** etc.

7. The various criteria in 1.3 should be succinctly presented in tabular form and placed in the results of the study as an evaluation of the results of this study is sufficient. A detailed interpretation is not required.

8. 2.2 should not appear in Methods, but Results.

Thank you for the suggestion but the measurements were the basis for making a full-season simulation and for this reason they were placed in "Methods and Measurements"

9. lines 352-360 should explain the reasons for the fluctuations in CO2 concentration and why CO2 dropped but did not drop below 1000 ppm.

It is explained in line 357.

10. lines 367-369, the authors state that 31 people would cause high CO2 concentrations, during which the windows were kept closed? Also, in schools in China, the average number of people in a classroom is 50 or more. Some studies on China, the results obtained are generally consistent with the results of this study.

"31" is the maximum amount of people which could occupy the analyzed classroom that’s why this specific number was referenced.

11. In the modelling section, the geometric dimensions, source settings, detailed methods (e.g. turbulence modelling, wall conditions, etc.), boundary conditions (entrance and exit settings), etc. are not represented. In short, the modelling methods section is not described in sufficient detail. Also, it is recommended to provide 3D modelling diagrams.

Simulations was made in CONTAM software – a multizone airflow and contaminant transport calculation tool and this is not a CFD tool . The classroom was modelled as one zone connected with outdoor with air flow paths represents: air leakage, windows opening, ventilation ducts and so on.

12. Why don't I see a cloud view of the pollutant distribution after the simulation? Is it because the simulation software used is different from CFD? Because I have not used this software.

Yes see comments to previous point.

13. Figures 5 and 6 are not described in the text. Model validation should be the result.

The info was added below the graphs:

Figure 5 presents the adjustment of the model to the measurements’ data. Black line represents simulation curve that follows the measurement results. Probability distribution and density are presented in Figure 6.

14. lines 439-446, missing references.

15. the font of the image is too small, please adjust it.

16. The authors simulated the CO2 pollution level in the classroom in winter. I would like to know what important results the authors got from the simulation. Because the author's simulation study is achievable through real measurements. Therefore, I don't think the simulation alone is significant.

The goal was to show that a simulation model could be validated based on several days of measurements, which could then be used to simulate IAQ for other use cases, ventilation, etc.

17. Please check the references. Please use literature from the last five years and check the citation format, e.g., missing volume and page numbers, and other issues.

18. Is it permissible to submit a check report with a result of 43%?

Author Response File: Author Response.docx

Reviewer 4 Report

Comments and Suggestions for Authors

The article evaluates the indoor environment of a primary school classroom in Poland by continuously measuring CO2, temperature, and humidity. It utilizes CONTAM software to build a classroom model, simulating air flow and ventilation strategies to validate the measured data. I find the following shortcomings in the logical reasoning and writing of the article:

1. The CO2 concentration data vary significantly between sensors 1 and 2 despite their close proximity in location. It would be beneficial to explain the reasons behind this discrepancy.

2. When validating the CONTAM model, would it be more convincing to separately compare the data from each sensor with the corresponding points in the model rather than comparing average CO2 concentrations?

3. Figure 4 lacks a legend. Are the positions of windows and air ducts depicted accurately?

4. Different conditions in Figure 12 should be distinguished using different markers or colors.

5. There are no textual descriptions found for Figures 13 and 14.

6. The article mentions that windows remain closed during classes due to noise. Does the discussion in Figure 12 regarding the impact of different window openings on air quality hold significance? Is it sufficient to draw the conclusions regarding mechanical ventilation? Does it offer guidance for determining the required mechanical ventilation rate?

Author Response

1. The CO2 concentration data vary significantly between sensors 1 and 2 despite their close proximity in location. It would be beneficial to explain the reasons behind this discrepancy.

The note about the location of sensor #2 was added in the table 2 and in the text. Sensor 2 is located outside the room on the external window sill.

2. When validating the CONTAM model, would it be more convincing to separately compare the data from each sensor with the corresponding points in the model rather than comparing average CO2 concentrations?

From the model we receive the average value of the concentration in the room space, so we believe that it is better to compare this value with the average of the measurements of all sensors.

3. Figure 4 lacks a legend. Are the positions of windows and air ducts depicted accurately?

This is a screenshot from CONTAM software, note added to the description.  

4. Different conditions in Figure 12 should be distinguished using different markers or colors.

The conditions changed smoothly as data changed throughout the simulation period.

5. There are no textual descriptions found for Figures 13 and 14.

The following text added to the article: 

Figure 13 shows the daily profile of concentrations and Figure 14 the daily profile of the ventilation air flows for the working days in the analyzed period of time. The indoor CO₂ concentration, even the min values all the time exceed level of 1000ppm. IAQ is low.   

6. The article mentions that windows remain closed during classes due to noise. Does the discussion in Figure 12 regarding the impact of different window openings on air quality hold significance? Is it sufficient to draw the conclusions regarding mechanical ventilation? Does it offer guidance for determining the required mechanical ventilation rate?

In case of this article the current usage profile is analyzed. In case of mechanical ventilation different the simulation steps are planned analyzing both opening of the windows and closed windows during entire usage time.  

 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I am sorry but the authors didn't take into account mostly of the suggestions I previously provided.

Moreover, in the literature there are several studies assessing CO2 concentration in indoor environment. 

The authors then should also better highlight their innovative contribution, i.e.:

The specific context of a primary school in Cracow, Poland.

Detailed validation of the CONTAM model with real measurement data.

Extended simulations for an entire heating season in Cracow's specific climatic conditions.

Proposal to utilize the validated model for simulating different ventilation strategies to improve IAQ.

Author Response

Moreover, in the literature there are several studies assessing CO2 concentration in indoor environment. 

Extended literature - added 11, 17, 18. 

The authors then should also better highlight their innovative contribution, i.e.:

The specific context of a primary school in Cracow, Poland.

The following part added to the abstract.

In the 1960s, over a thousand schools using similar technology were built in Poland. Most of them are still in use, and in many cases modernization works are being carried out to improve the building envelope and comfort of use. The analyzed school is one of several hundred similar ones in southern Poland. Therefore, analyzing the possibilities of improving IAQ is an important topic and the results can be used in the modernization process of many other buildings. 

Detailed validation of the CONTAM model with real measurement data.

Explained in abstract:

Article shows the usefulness of CONTAM for modeling not only gravity ventilation, but also the window opening process. The validated CONTAM model will be next utilized to simulate annual IAQ conditions under various ventilation strategies to identify the most effective methods for keeping acceptable IAQ while minimizing energy consumption. In the further analysis the validated model will be used to test the following systems: DCV (demand controlle ventilation) exhaust ventilation, DCV balanced ventilation with heat recovery.

Extended simulations for an entire heating season in Cracow's specific climatic conditions.

The specific period of time was chosen as during those specific months usage pattern is similiar and can be analyzed withe the model assumptions. Heating season in Poland is longer however if the temperatures are higher window opeining scheme is different.

Proposal to utilize the validated model for simulating different ventilation strategies to improve IAQ.

The following note added to the abstract.

In the further analysis the validated model will be used to test the following systems: DCV (demand controlle ventilation) exhaust ventilation, DCV balanced ventilation with heat recovery.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Maybe I didn't understand the author of the first comment I made on the manuscript. But what does it mean that the author neither modifies nor explains some of the comments?

1. The introduction section is too long. The literature review section could be set up as a separate second section. Alternatively, the literature review section should be concise and described in summarizing language.

2. the statement in lines 16-17 of the abstract. the conclusion that excessive CO2 means poor air quality is debatable. Indoor air quality can be evaluated by calculating a specific index.

3. the various criteria in 1.3 should be listed succinctly in a table and placed in the results of the study, as an assessment of the results of this study is sufficient. Detailed explanations are not needed.

4. The font size of the image is too small, please adjust it.

5. Please check references. Please use literature from the last five years and check the citation format. The format is not uniform.

6. the check result is 43%. please explain to the authors.

7. The purpose of the author's simulation is to demonstrate the validity of the simulation model. Then this article is meaningless and can only be used as a pre-validation for subsequent studies. Many such studies already exist and the workload includes other contaminants. Furthermore, there is nothing innovative about using software to model and validate, and it is a basic operation. If it is not done correctly, the next step in the study cannot be taken afterwards.

Comments on the Quality of English Language

No.

Author Response

1. The introduction section is too long. The literature review section could be set up as a separate second section. Alternatively, the literature review section should be concise and described in summarizing language.

The literature review was separated as a different part (section 2).

2. the statement in lines 16-17 of the abstract. the conclusion that excessive CO2 means poor air quality is debatable. Indoor air quality can be evaluated by calculating a specific index.

We have added the sentence in the abstract about different aspects affecting the IAQ but also emphasized the fact that we focused only on the CO2 level. 

3. the various criteria in 1.3 should be listed succinctly in a table and placed in the results of the study, as an assessment of the results of this study is sufficient. Detailed explanations are not needed.

Thank you very much for the suggestion but we woudl like to keep it this way as the other reviewers did not comment on that. 

4. The font size of the image is too small, please adjust it.

Adjusted. 

5. Please check references. Please use literature from the last five years and check the citation format. The format is not uniform.

Added new articles (11, 17, 18)

6. the check result is 43%. please explain to the authors.

7. The purpose of the author's simulation is to demonstrate the validity of the simulation model. Then this article is meaningless and can only be used as a pre-validation for subsequent studies. Many such studies already exist and the workload includes other contaminants. Furthermore, there is nothing innovative about using software to model and validate, and it is a basic operation. If it is not done correctly, the next step in the study cannot be taken afterwards.

The aim of this article was to emphesize the poor quality of existing ventilation systems in the schools where opening of the windows is limited due to the usage patern. The conducted measurements allowed for validation of model which first of all proved that those negative conditions are due to the entire heating season but also gives the possibility of the further simulation of different ventilation systems. Different mechanical ventilation systems will be modeld and analysed, mostly the ones controlled by the level of CO2 in the internal environment.  

Note about that added in the abstract of article. 

Article shows the usefulness of CONTAM for modeling not only gravity ventilation, but also the window opening process. The validated CONTAM model will be next utilized to simulate annual IAQ conditions under various ventilation strategies to identify the most effective methods for keeping acceptable IAQ while minimizing energy consumption. In the further analysis the validated model will be used to test the following systems: DCV (demand controlle ventilation) exhaust ventilation, DCV balanced ventilation with heat recovery.

Author Response File: Author Response.docx

Reviewer 4 Report

Comments and Suggestions for Authors

No more comments.

Author Response

Thank you for the revisions and comments. 

Round 3

Reviewer 3 Report

Comments and Suggestions for Authors

The authors still have not resolved the issue of why the check result is 43%.

 

 

Author Response

The authors still have not resolved the issue of why the check result is 43%.

Text of article was revised and now the similiarity index is 25%. 

 

 

Author Response File: Author Response.docx

Round 4

Reviewer 3 Report

Comments and Suggestions for Authors

I don't have any more questions. The article can be accepted now.

Comments for author File: Comments.docx