Assessing BME688 Sensor Performance Under Controlled Outdoor-like Environmental Conditions

Highlights What are the main findings? BME688 sensors show consistent normalized responses across devices but require individual baseline calibration. Each gas (NO2, CO, SO2, isobutylene) has an optimum operating temperature in the 360-400 degrees C range, with fast and stable responses. Humidity enhances CO sensing via hydroxyl pathways but reduces sensitivity and stability for other gases. What is the implication of the main finding? BME688 can be deployed in outdoor/mobile air quality networks if calibration and compensation for temperature/humidity are applied. The findings support robust, low-cost IoT platforms bridging lab characterization and real-world monitoring.Highlights What are the main findings? BME688 sensors show consistent normalized responses across devices but require individual baseline calibration. Each gas (NO2, CO, SO2, isobutylene) has an optimum operating temperature in the 360-400 degrees C range, with fast and stable responses. Humidity enhances CO sensing via hydroxyl pathways but reduces sensitivity and stability for other gases. What is the implication of the main finding? BME688 can be deployed in outdoor/mobile air quality networks if calibration and compensation for temperature/humidity are applied. The findings support robust, low-cost IoT platforms bridging lab characterization and real-world monitoring.Abstract Low-cost miniaturized gas sensors are increasingly considered for outdoor air quality monitoring, yet their performance under real-world environmental conditions remains insufficiently characterized. This work evaluates the dynamic gas response of the Bosch BME688 sensor, whose metal oxide sensing layer is based on tin dioxide (SnO2) material, focusing on its sensitivity, selectivity, and dynamic response to four representative air pollutants: nitrogen dioxide (NO2), carbon monoxide (CO), sulfur dioxide (SO2), and isobutylene. This study provides both quantitative performance metrics and a physicochemical interpretation of the sensing mechanism. Controlled experiments were conducted in a custom test chamber to facilitate the precise regulation of temperature, humidity, and gas concentrations in the ppm to sub-ppm range. Despite large variability in the baseline resistance across devices, normalization yields consistent behavior, enabling cross-sensor comparability. The results show that the optimum operating temperatures fall in the range of 360-400 degrees C, where response and recovery times are reduced to a few minutes, compatible with mobile sensing requirements. Moreover, humidity strongly influences sensor behavior: it generally decreases sensitivity but improves kinetics, and in the case of CO, it enables enhanced responses through additional hydroxyl-mediated pathways. These findings confirm the feasibility of deploying BME688 sensors in distributed outdoor monitoring platforms, provided that humidity and temperature effects are properly addressed through calibration or compensation strategies. In addition, the variability observed in baseline resistance highlights the need for normalization and, consequently, individual calibration steps for each sensor under reference conditions in order to ensure cross-sensor comparability. The findings provided in this study provide support for the design of robust, low-cost air monitoring networks.