The results are used for smog warning.

Measurement method (half hour measurements)

Sulfur dioxide (SO2) is measured by ultraviolet fluorescence. The air is drawn into a chamber which is illuminated with ultraviolet light. The SO2 molecules are estimated by the ultraviolet light and when they return to the normal state, light is emitted with a longer wavelength. By recording this light in a photosensor, one can determine the concentration of SO2.

Technical description

• Analyzing method: UV-fluorescence.
  SO₂ monitors:
• Principle: Fluorescence measurements by UV radiation.
• Measuring range: 0-500 ppb, at 0.6-0.8 l/min.
• Lower detection limit: <1 ppb
• Precision ±5%
• Selectivity: NO gives a positive interference of approx. 2%.
• Routine checks: Automatic zero point check every day around midnight with zero- air from a generator. Automatic span check once a week with around 200 ppb SO₂ in syntetic air from a pressure bottle.
• Calibration at the laboratory: 1) Diluted reference gas (from Messer Griesheim) of 12 ppm of SO₂in syntetic air. 2) Diluted SO₂ gas from a permeation tube. 

24 hour measurements SO2:

Collected on KOH-impregnated filters and analyzed by ion chromatography.

Particular sulfur:

Analyzed as:

• Sulfate by ion chromatography
• Total sulfur with PIXE. See Elements