This well-written manuscript reports the performance of a wearable particulate matter (PM) monitor, Black Beauty (BB), in measuring PM exposure in horses fed with dry versus soaked hay. Calibration with Tapered Element Oscillating Microbalances (TEOMs) showed high correlation but underestimation of PM levels by BB monitors. The study demonstrated significant reductions in PM2.5 and PM10 levels when horses were fed soaked hay compared to dry hay, highlighting the potential of soaking hay to mitigate dust exposure.

The study offers important information for equine asthma research:
- The use of a custom-built, wearable PM monitor for horses represents a novel method for evaluating PM exposure in equine environments.
- The results demonstrate a high degree of correlation between BB monitors and reference TEOMs, ensuring reliable data despite the underestimation bias.
- The findings conclusively demonstrate that soaking hay significantly reduces PM exposure, which is crucial for managing equine respiratory health.

I only have minor questions that could be interesting for the reader to include in the discussion:

• The authors discuss that differences in individual horse behavior can significantly affect PM exposure levels, which was not extensively accounted for in the study. How could behavioral variability be accounted for in future experiments.

• Isn’t the lack of data on PM 4 (respirable particles?) a limitation of the device? Given that the device considerably underestimates PM 2.5 , and even more PM 10, do you expect that PM 4 can be reliably extrapolated from PM 2.5 and PM 10 data?

• The authors stress that the new custom-built wearable device is more affordable and practical (lightweight) than other particle counters previously used for research in equine asthma. Do you expect that the new device could be applicable mainly for research, or also in clinical practice? Given the limited sample size, conduction of the experiments in acclimate-controlled barn and lack of clinical data, would any further tests or experiments be needed to assess the stable environment in clinical cases?

• The authors report the 20-minutes and 8-hours. From the report it seems that continuous data were available – could other time intervals be extracted or could analyses of continuous data be interesting for other research questions or clinical applications?