Table 1 in Long et al. lists the Thermo Scientific model 49i monitor that was used in their study as having been equipped with a MnO₂ catalyst.  This is also mentioned in their text, section 2.1.2. first sentence.  To the best of my knowledge, this has been and still currently is the default, and only configuration, in which this monitor can be purchased from Thermo Scientific.  I cannot trace from where Bernays et al. got the information that the monitor used by Long et al. had a different, i.e. a MnCl₂ scrubber.  I don’t remember ever seeing an ozone UV absorption monitor that used an MnCl₂ scrubber.  This is an important piece of missing information.  This certainly needs to be clarified by Bernays et al. before their comment should be accepted for final publication.  Furthermore, Long et al. should be given an opportunity to comment on this question.