I agree with the authors and one of the reviewers that the authors have largely done a good job and the manuscript is much improved. However, both reviewers still express reservations about the description of the use of the PAM reactor in the manuscript. The description of the treatment and interpretation of the measurements should be expanded further to alleviate the concerns of the reviewers. Both have made suggestions and these should be borne in mind in the expanded discussion. In particular, some discussion of the impacts of the likely reactivity of the VOC mixture (during cold and hot running conditions) on the OH and non-OH chemistry in light of the current knowledge of PAM reactor chemistry should be included. The concern about collection efficiency should also be addressed or clarified. Owing to the technical nature of the required additions, I may need to send the manuscript back to the reviewers and hence have selected "major revisions", though do not expect the revisions to extend beyond these matters.

The authors have included the further analysis and discussion required following the second round of referee comments and the manuscript is now suitable for publication. The paper makes a novel and significant contribution to the literature and the authors are to be commended on the revised manuscript.