This is an interesting, but very long review article. It is generally well-written, except some parts (e.g., pages 32-34) are almost completely merely lists of concentrations reported in different studies. Here are some ideas on how the text could be to shortened and made more readable:
- Move Table 1 to online supplement
- Instead of listing concentrations reported in different studies, show the results in summary tables or figures (such as Figures 2 and 3) and then only briefly describe the concentration ranges and the interpretation of the results in the text.
In some parts of the write-up, interpretation of the results is missing. It is important to always also interpret the results: are the reported concentrations high or low when compared to guideline values or some other reference data.
Minor comments:
1. Concentration of CO2 and CO are sometimes given in ppm and sometimes in mg/m3 or ug/m3. It would be good to convert all values to ppm to make them comparable between studies. (Similar to what you have done for CO on lines 651-652.
2. Line 528: please spell out “FP”
3. Lines 533-536: “Global warming” is listed as a pollutant. Also, one-sentence paragraphs should be avoided.
4. Line 537: “alternate” should be “alternata”
5. Lines 692-694: units are missing here

The authors have sufficiently addressed my previous comments.