Can Air Quality Gas Sensors Be Used for Emission Monitoring of Small-Scale Local Air Pollution Sources? Pilot Test Evaluation

Round 1

Reviewer 1 Report

1.      Please improve the introduction section. (a) The author can start with the basic need of air quality monitoring using a gas sensor. (b) different previously available air quality monitoring methods with the sensing material used and their limitation, then the advantage of the author’s methods against the previously available research. Kindly add the following in the appropriate place, (page 1).

(i) https://www.pubs.thesciencein.org/journal/index.php/jmns/article/view/282

(ii) https://doi.org/10.1016/j.sna.2021.113111

2. Can the author present the experiment to show the lower detection limit of CO gas.

3. Please introduce the experimental data related to cross selectivity of sensor towards CO, NO and CO2 gases?

4. Please provide information about the detailed sensing mechanism of such sensor?

5. Can you please elaborate the reason behind “the PID-AH9 sensor is almost inactive during the measurement, even though the anticipation was that it would respond to higher concentrations at low dilution”. (page 15, line 433)

Author Response

1) This manuscript is focused on use of sensors We have published 2 articles focused on air quality monitoring using low-cost sensors recently. Those articles are referenced as nr. 13 and 26 and they deal with benefits and use of sensors in air quality measurements. Discussion has been reviewed with contribution of suggested articles.

2-4) There was no experiment ot verify(prove) lower CO detection limit. The sensors were not checked for cross-sensitivity as the primary focus was in evaluation of simple use and monitoring whether the harsh environment shortens the sensor's service life.

5) The section has been rewritten.

Reviewer 2 Report

All figures should be reviewed and potentially revised before publication.  Figures should have clear, legible x and y axis labels with SI units for all. Figures should be of uniform size or use subplots for comparisons. Figs 6(a) and (b) may be more impactful as semilog plots (y-axis log scale).   

Author Response

The text has been reviewed, also language-wise.

Figures were reviewed and numbering fixed. Mentioned figures for comparison uploaded as attachment. In our opinion, the logarythmic scale of concentration does not improve the meaning of the figure. 

Author Response File: Author Response.docx

Reviewer 3 Report

This paper provides the results of a pilot test evaluation for investigating the applicability of low-cost sensors for monitoring small-scale pollution sources such as domestic boilers. In general, the paper is well-written and easy to follow. The method for the statistical comparison is very comprehensive and scientifically sound. The results of this study would be of great interest to both researchers and practitioners in the field of air quality monitoring.  In particular, they show the applicability of low-cost sensors for emission monitoring of local pollution sources, as long as proper dilution is first applied. An interesting venue for future research, would be to incorporate the dilution process into the low-cost sensors.

 Some minor comments:

1.       The script used for multi-channel data collection is not discussed in the manuscript 

2.       Τhe calibration procedure of the low-cost sensors is not discussed in the manuscript

3.       Section 2.1. Monitored parameters: Authors did not clarify the parameters used in their experiment 

4.       Line 192 The term PTFE should be explained 

5.       Figure 4 is not discussed in the manuscript 

6.       Figure 5 is missing from the manuscript 

7.       Figure 8 and 9 size should be improved 

8.       There are some minor typo-grammatical errors throughout the manuscript 

Author Response

1. The script used for multi-channel data collection is not discussed in the manuscript - Added and described
2. Τhe calibration procedure of the low-cost sensors is not discussed in the manuscript - Added and described
3. Section 2.1. Monitored parameters:Authors did not clarify the parameters used in their experiment - added reference to EU and Czech legislation documents
   
4. Line 192 The term PTFE should be explained - added
5. -7 Figures checked and numbering fixed

8.       There are some minor typo-grammatical errors throughout the manuscript - Text Reviewed