Odor from Building Air Conditioners: Emission Characteristics, Odor Compounds and Influencing Factors

Round 1

Reviewer 1 Report

In this paper, the effect of air conditioning operation on indoor odor is studied. By testing of odor emission from air conditioner outlet and air filter, the main components of odor compounds and the main factors affecting odor intensity were obtained. This paper is well organized and it has certain scientific value for controlling indoor air conditioning odor. it is recommended to accept publication after minor revision. The following are a few suggestions.

1. Regarding the personnel's odor evaluation, whether the prolonged time will lead to the olfactory passivation, affecting the subjective evaluation results. If the test subjects were given fresh air during the non-evaluation phase, the results would be more reliable.

2. The relative humidity of the room will affect both the water content of the filter and the condensing water on the surface of the evaporator. Thus, the influence of indoor relative humidity on the odor should be taken into consideration.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

This paper investigated VOCs emitted from air conditioners operated in several different environments. The study is interesting, but some key methods details are missing that would improve the clarity of the paper. I suggest publication after revisions have been completed. English language editing is also required for clarity. Some issues are detailed below.

Line 18: Instead of “maybe” I think the authors mean “may be”.

Line 31-32: Do not start sentence with “And”; combine two sentences or start the second with “Also,”.

Line 42: Use “recent”, not “recently” here.

Line 47: Remove the period after [32] if that is not the end of the sentence.

Lines 155-158: Consider breaking up this sentence and clarifying lines 157-158. Should “study” be “studying”?

Line 158: Should “odor” be “order” here?

Figure 1: It is not clear what “12-10-8-6-4-2-4 min” means. Add some text in the figure legend to explain.

Line 177, Table 2: What type of TD unit was used for desorption of Tenax-TA tubes, and what were the method parameters? This has not been included

Table 2: Why was Nitrogen chosen for carrier gas instead of helium? This is not ideal and reduces sensitivity.

Table 2, oven temp: what does the number in parentheses mean? For example, 50 degrees (2)-9C/min-130(1), etc, is not clear what the (2) and (1) represent. If it is hold time this needs to be stated in table legend but there are better was to represent the gradient.

Table 2: Why isn’t a scan range provided for the Tenax-TA analysis?

Table 2: What was the quadrupole temperature used for the 5975B MSD for Tenax-TA analysis? That should be included. For scan range of Supelco tubes, I think you mean “m/z” and not “z” for units?

Line 177, Table 2: Please include details for sorbent extractions.

Line 192-193: This sentence does not make sense. How would odorants not be guaranteed to have characteristics of odor?

Line 205: “1” should be “3” for Results and Analysis section.

Line 219-221: What data were used to determine this?

Line 231-232: Odor intensity values should be included in methods or footnotes.

Figure 4: It is unclear what analysis the data in this figure come from. Please clarify in the figure legend how these data were collected (eg, Tenax, DNPH?).

Table 3: How were these compounds identified, and which sample analysis does this come from? Were standards run to identify compounds based on retention time and spectra, or was a NIST library used?

Line 270, Table 4: Why are some rows shown in bold?

Table 6: What does it mean if check mark is shown without a superscripted number? Why is ethyl acetate shown in bold?

Line 326: Add “a” for the first part of figure.

Line 374: Discussion should be section 4, not 1.

Line 391: Conclusion should be section 5, not 1.

Line 400-402: What data are being used to make this conclusion? Be specific.

Line 403-404: This is a hypothesis, not a conclusion, since this was not demonstrated in the paper.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The manuscript is somewhat improved after this revision; however, there were some errors introduced as typos during revision, and other comments were not addressed in the revision. More corrections need to be made before this paper is acceptable for publication.

Errors that have not been corrected:

Line 31-32: Sentence now starts with “Alsond”. Please delete the “nd” from the end of “Also”.

Line 42: It should be “recent years”, not “recently years”.

Line 47: Remove the period after reference [32] since it is not the end of the sentence.

Line 158: The correct word “order” was added, but “odor” needs to be deleted from before it. “in odor order to avoid the influence…” does not make sense.

Line 177, Table 2: TD unit parameters: the type of trap used is still missing, please add. The trap heating rate has also been omitted, please add. Were inlet or outlet splits used?

Table 2: He has been added for carrier gas for GC/MS in column flow row, but N2 has not been deleted. Please delete N2.

Line 195-196: Please clarify this sentence, “However, the odorants identified by this method can only be guaranteed to have the characteristics of odor.” How would odorants not be guaranteed to have characteristics of odor?

Line 205: “3” was added for the Results and Analysis section, but the “1” needs to be deleted or it reads “31”.

Table 3: How were the compounds not present in Flavornet detected? Were standards run to identify compounds based on retention time and spectra, or was a NIST or other mass spectral library used? How certain are the identifications (what are the criteria?).

Table 6: What does it mean if check mark is shown without a superscripted number?

Line 331: Add “a” for the first part of figure, I assume for Ethyl acetate. The letters need to be more clearly associated with the figures.

Line 340, Figure 7: What are the temperature setpoints of CFAC #1-3?

Line 378: Discussion should be section 4, not 14.

Line 396: Conclusion should be section 5, not 51.

Line 405-407: What data are being used to make this conclusion? Be specific. Acetic acid has a sour odor and acetaldehyde has a pungent/ether odor. What is the rationale that these compounds are more responsible than others for the cool-off period.

Line 408-409: Please expand on this. The increase in which compounds specifically lead to this conclusion? What about hydrophilic compounds that do not increase in concentration at higher temperature setpoints? How was this tested?

Author Response

Please see the attachment.

Author Response File: Author Response.docx