On July 20, 2025, the air quality in Basel was generally within acceptable limits for most pollutants. The maximum concentration of ozone (O₃) reached 93.5 µg/m³, with an average of 61.75 µg/m³. Nitrogen dioxide (NO₂) had a maximum of 12.8 µg/m³ and an average of 6.85 µg/m³. Particulate matter (PM2.5) recorded a maximum of 7.7 µg/m³ and an average of 5.85 µg/m³. Particle count concentration (CPC) peaked at 11,250.7 particles/cm³, averaging 5,994.92 particles/cm³. Elemental carbon (EC) levels were low, with a maximum of 0.3 µg/m³ and an average of 0.18 µg/m³. Sulfur dioxide (SO₂) was minimal, with a maximum of 0.4 µg/m³ and an average of 0.2 µg/m³. Nitrogen oxides (NOx) had a maximum of 13.8 µg/m³ and an average of 8.19 µg/m³.

Comparing these values to historical data since 2018, the ozone levels were below the recent 30-day average of 82.66 µg/m³ and the seasonal average of 78.44 µg/m³. NO₂ levels were slightly below the recent 30-day average of 6.91 µg/m³ and the seasonal average of 7.33 µg/m³. PM2.5 concentrations were below both the recent 30-day average of 7.33 µg/m³ and the seasonal average of 8.81 µg/m³. CPC values were lower than the recent 30-day average of 6,635.76 particles/cm³ and the seasonal average of 6,785.27 particles/cm³. EC levels were consistent with the historical averages. SO₂ concentrations were significantly below the recent 30-day average of 0.45 µg/m³ and the seasonal average of 0.49 µg/m³. NOx levels were slightly above the recent 30-day average of 7.93 µg/m³ but below the seasonal average of 8.34 µg/m³.

Overall, the air quality on July 20, 2025, was generally in line with historical norms, with most pollutants showing typical or below-average concentrations. The slightly elevated NOx levels compared to the recent 30-day average could be attributed to local traffic or industrial activities, but they remained within acceptable limits. No significant deviations from historical air quality patterns were observed on this day.