Respiratory Rate Monitoring During Wildland Firefighting Operations: A Comparison of Face-Mounted and Chest-Mounted Wearable Sensors

Despite its critical role in assessing physiological strain and mitigating heat- and smoke-related risks, real-time respiratory monitoring is still largely absent in wildland firefighting. This study evaluates two wearable systems for estimating respiratory rate (RR) under operational field conditions (i.e., a multistage fire suppression protocol): a facemounted system based on a thermistor integrated into a FFP3 facemask (Mask) and a chest-worn commercial strap (Bioharness, BH) with an integrated strain sensor. RR was estimated from raw signals using frequency-domain analysis considering both 25 s and 50 s windows lengths. Pairwise comparisons were performed between RR values estimated from Mask and BH, and respectively between each of them and the manufacturer-generated “Summary RR” provided by the BH's onboard processor. Results underscore the influence of signal processing over sensor placement and demonstrate the feasibility of unobtrusive RR tracking using both wearable systems in dynamic, high-risk environments.