Development and Evaluation of a Portable Dilution-Based Gas Mixer System for On-Site Calibration of Low-Cost Sensors in Ambient Air Monitoring

Low-cost sensors are increasingly being used to measure various fields, including environmental monitoring. However, their accuracy relies on regular calibration using known gas mixture concentrations. This study presents the development and evaluation of a portable dilution-based gas mixture (DGM) system designed for on-site calibration of low-cost oxygen sensors. The system utilizes 99.999 %mol/mol oxygen and nitrogen gases blended via two portable mass flow controllers, operated by a LabVIEW interface. Calibration was performed at 30 %mol/mol, 60 %mol/mol, and 90 %mol/mol oxygen concentrations, and validated using certified reference gas mixtures. The observed measurement errors were 0.046 %mol/mol, –0.002 %mol/mol, and –1.952 %mol/mol, respectively. These results confirm high accuracy and repeatability, aligning with the Indonesian standard SNI 9178:2023. This system provides a cost-effective, traceable, and field-deployable solution for sensor calibration, which is particularly beneficial for expanding the monitoring of ambient air quality in resource-limited settings.