Fig. 1. The amount of nitrogen dioxide detected versus the amount previously added, both by the CLS method (dashed) and by our new algorithm (solid). The curves show that the new algorithm shows a linear response down to better than 4.5 × 10⁻⁷% whereas the CLS approach is linear down to about 4 × 10⁻⁵%.

Fig. 2. The amount of sulfur dioxide detected versus the amount previously added to the mixture, both by the CLS method (dashed) and by CSM algorithm (solid). The curves show that the new algorithm reveals a linear response down to around 7.8 × 10⁻⁶% whereas the CLS approach is linear down to about 2.5 × 10⁻⁴%.

Fig. 3. The amount of carbon monoxide detected versus the amount previously added, both by the CLS method (dashed) and by CSM algorithm (solid). The two approaches show good behavior down to 1.7 × 10⁻⁶%.

Fig. 4. The amount of carbon dioxide detected versus the amount previously added, both by the CLS method (dashed) and by CSM algorithm (solid). The two approaches show nearly the same behavior down to 2 × 10⁻³%.

Fig. 5. The results of the field study which has been conducted by analyzing samples from an industrial zone in 8 weeks to monitor the level of air pollutants. The absorbance spectrum of these samples is measured using FTIR MB3000 spectrometer. Then, the CSM algorithm is applied to the obtained absorbance spectrum to determine the amount (ppm) of SO₂, NO₂, and CO in these samples.

Fig. 6. The results of the field study which has been conducted by analyzing samples from an industrial zone in 8 weeks to monitor the level of air pollutants. The absorbance spectrum of these samples is measured using FTIR MB3000 spectrometer. Then, the CSM algorithm is applied to the obtained absorbance spectrum to determine the amount (ppm) of CO₂ in these samples.

Fig. 7. An aerial view showing the location of the road tunnel in Riyadh city.