Author(s)

Adel Bassuoni Shehata^*, Abdulrahman Rashed Al Askar, Najjy Hamad Al Yami, Abdullah Suleiman Al Owaysi, Sultan K. Alharbi

Chemistry Department, National Measurement and Calibration Center (NMCC), Saudi Standards, Metrology and Quality Organization (SASO), Riyadh, Kingdom of Saudi Arabia.

Global efforts for environmental cleanliness through the control of gaseous emissions from vehicles are gaining momentum and attracting increasing attention. Calibration plays a crucial role in these efforts by ensuring the quantitative assessment of emissions for informed decisions on environmental treatments. This paper describes a method for the calibration of CO/CO₂ monitors used for periodic inspections of vehicles in cites. The calibration was performed in the selected ranges: 900 - 12,000 µmol/mol for CO and 2000 - 20,000 µmol/mol for CO₂. The traceability of the measurement results to the SI units was ensured by using certified reference materials from CO/N₂ and CO₂/N₂ primary gas mixtures. The method performance was evaluated by assessing its linearity, accuracy, precision, bias, and uncertainty of the calibration results. The calibration data exhibited a strong linear trend with R² values close to 1, indicating an excellent fit between the measured values and the calibration lines. Precision, expressed as relative standard deviation (%RSD), ranged from 0.48 to 4.56% for CO and from 0.97 to 3.53% for CO₂, staying well below the 5% threshold for reporting results at a 95% confidence level. Accuracy measured as percent recovery, was consistently high (≥ 99.1%) for CO and ranged from 84.90% to 101.54% across the calibration range for CO₂. In addition, the method exhibited minimal bias for both CO and CO₂ calibrations and thus provided a reliable and accurate approach for calibrating CO/CO₂ monitors used in vehicle inspections. Thus, it ensures the effectiveness of exhaust emission control for better environment.

Monitors, Periodic Inspection, CO/CO₂ Calibration, Linearity, Precision, Accuracy

Shehata, A. , Askar, A. , Yami, N. , Owaysi, A. and Alharbi, S. (2024) Calibration of CO and CO₂ Monitors Used in Periodic Inspection of Vehicles at Fixed Stations for Environmental Control. Green and Sustainable Chemistry, 14, 29-41. doi: 10.4236/gsc.2024.142003.