Dear Dan,

I carefully went through your replies and the resubmitted manuscript. To my mind, you thoroughly addressed the reviewers’ concerns. I appreciate that you tried to reduce the length of the manuscript even if it was shortened by only a fraction of the 50% reduction suggested by reviewer 2. I agree with you that AMT is the right platform for this type of rather detailed technical description (which was kind of criticized by reviewer #1). Your contribution is providing very valuable information and can be considered to be a key reference for future users of similar FTIR systems.

I just stumbled upon a few more minor issues and technical corrections which I suggest to be made prior to publication:

I am wondering why you abbreviate “quality assurance and quality control” as “QC/QA” and not as “QA/QC”; QA/QC is the more common term and also corresponds to the spelled-out order.

Figure 3 is labelled with a topleft (a). Remove the label.

Page 12 still contains a crossed-out sentence.

Page 25 still contains a crossed-out sentence.

Figure 12: y-axis range, panel c: start at 290 or 300 ppb? Y-axis range, panel a: start at 1600 ppb, move legend to panel b (if there is no space for the legend in panel a anymore)

Re the grey vertical dashed lines illustrating the instrument events which are only explicitly mentioned in the caption of Figure 3: I wouldn’t add the same statement in all other captions of the figures containing these lines but you may find some space for the legend “FTIR instrument events ---“ in one of the panels of each subsequent figure.

Especially Fig. 16 (but also several others figures showing some boxplot; Figs. 3, 4, 11, 14): I couldn’t find any explanation what the boxes, whiskers and ticks represent.

Kind regards,

Martin Steinbacher