On July 23, 2025, the air quality in Basel showed a mix of typical and slightly elevated pollutant levels. Ozone (O₃) had a maximum concentration of 90.9 µg/m³ and an average of 61.96 µg/m³. Nitrogen dioxide (NO₂) levels reached a maximum of 16.9 µg/m³ with an average of 7.18 µg/m³. Particulate matter (PM2.5) recorded a maximum of 5.0 µg/m³ and an average of 3.45 µg/m³. The concentration of particles counted by CPC peaked at 15,433.6 particles/cm³, averaging 7,936.27 particles/cm³. Elemental carbon (EC) had a maximum of 0.3 µg/m³ and an average of 0.13 µg/m³. Sulfur dioxide (SO₂) levels were low, with a maximum of 1.0 µg/m³ and an average of 0.31 µg/m³. Nitrogen oxides (NOx) showed a maximum of 28.0 µg/m³ with an average of 9.35 µg/m³.

Comparing these values to historical data, the average O₃ level was below the recent 30-day average of 79.05 µg/m³ and the seasonal average of 77.4 µg/m³, indicating lower than typical ozone levels. NO₂ levels were slightly above the 30-day average of 6.58 µg/m³ but aligned with the seasonal average of 7.2 µg/m³. PM2.5 concentrations were significantly below both the 30-day and seasonal averages of 6.63 µg/m³ and 8.48 µg/m³, respectively. CPC levels were higher than the 30-day average of 6,303.23 particles/cm³ and the seasonal average of 6,712.82 particles/cm³, indicating an increase in particle count. EC levels were below both the 30-day and seasonal averages of 0.18 µg/m³ and 0.22 µg/m³, respectively. SO₂ concentrations were below the 30-day average of 0.4 µg/m³ and the seasonal average of 0.47 µg/m³. NOx levels were slightly above the 30-day average of 7.68 µg/m³ but within the seasonal average range of 8.24 µg/m³.

Overall, the air quality on July 23, 2025, was mostly within historical norms, with the exception of an increased particle count as indicated by CPC measurements. This could suggest a temporary rise in particle emissions or changes in atmospheric conditions affecting particle dispersion. Other pollutants remained within or below typical ranges, suggesting no significant deviation from expected air quality conditions for this time of year.