🌿 SO₂ in air (UV fluorescence)
In short
Continuous automatic measurement of sulfur dioxide (SO₂) concentration in ambient air by ultraviolet fluorescence method. The test is performed according to PN-EN 14212:2013; Measurement range: 0–500 µg/m³ (typical), expandable to 2000 µg/m³. The procedure comprises 6 steps (about 3 h 30 min in total); it is used for: National Environmental Monitoring (GIOŚ/WIOŚ stations), Emission monitoring from coal power and heating plants, Urban air quality assessment.
At a glance
- Standard: PN-EN 14212:2013
- Category: Environmental
- Procedure steps: 6
- Total time of stages: 3 h 30 min
- Measurement range: 0–500 µg/m³ (typical), expandable to 2000 µg/m³
- Detection limit: 0.5–2 µg/m³
- Response time (T90): <120 s
Overview
Sulfur dioxide (SO₂) is a gaseous air pollutant formed mainly from combustion of sulfur-containing fossil fuels (coal, fuel oil). SO₂ is toxic to the respiratory system, causes acid rain and smog.
Standard PN-EN 14212 defines the reference method for continuous SO₂ measurement in ambient air, based on UV fluorescence. The method is used in the National Environmental Monitoring (PMŚ) network managed by GIOŚ/WIOŚ. Permissible SO₂ concentrations: 350 µg/m³ (1h), 125 µg/m³ (24h) according to Directive 2008/50/EC and Polish regulation.
Method principle
The air sample is drawn into the analyzer measurement chamber, where it is irradiated with UV radiation at ~214 nm wavelength. SO₂ molecules absorb UV radiation and transition to an excited state, from which they return to the ground state emitting fluorescence at longer wavelength (~330 nm). Fluorescence intensity is proportional to SO₂ concentration and measured by photomultiplier. Interferences (e.g., H₂O, aromatic hydrocarbons) are eliminated by selective optical filter and Teflon membrane.
Applications
- National Environmental Monitoring (GIOŚ/WIOŚ stations)
- Emission monitoring from coal power and heating plants
- Urban air quality assessment
- Monitoring protection zones around industrial plants
- Early warning systems for air pollution
Key parameters
| Parameter | Value |
|---|---|
| Measurement range | 0–500 µg/m³ (typical), expandable to 2000 µg/m³ |
| Detection limit | 0.5–2 µg/m³ |
| Response time (T90) | <120 s |
| 1h limit | 350 µg/m³ (not to exceed >24 times/year) |
| 24h limit | 125 µg/m³ (not to exceed >3 times/year) |
Standard
- Standard number
- PN-EN 14212:2013
- Title (PL)
- Powietrze atmosferyczne — Standardowa metoda pomiaru stężenia dwutlenku siarki metodą fluorescencji w ultrafiolecie
- Title (EN)
- Ambient air — Standard method for the measurement of the concentration of sulphur dioxide by ultraviolet fluorescence
Step-by-step procedure
-
Analyzer installation
Place analyzer in monitoring station with air conditioning (20±5°C). Connect inlet probe and Teflon line.
-
Startup and stabilization
Turn on analyzer. Heat UV lamp (30–60 min). Check sample flow (0.5–1 L/min).
-
Zero calibration
Supply zero air. Set analyzer zero point. Deviation <2 µg/m³.
-
Span calibration
Supply SO₂ calibration gas of known concentration (e.g., 200 µg/m³). Set span point. Deviation <5%.
-
Continuous measurement
Start automatic data recording (1-minute and hourly averages). Data transmission to GIOŚ database.
-
Quality control
Zero and span calibration every 2 weeks. Service every 6 months. UV lamp replacement every 12–18 months.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| SO₂ analyzer (UV fluorescence) | Thermo 43i, Horiba APSA-370, Teledyne T100 | 30,000–60,000 PLN |
| Gas calibrator (permeation or cylinders) | Thermo 146i, Environics 6100 | 25,000–60,000 PLN |
| Zero air generator (synthetic air) | Thermo 111, carbon filter + dryer + HEPA filter | 10,000–25,000 PLN |
| Sample intake system with probe | PM₁₀ probe with filter and Teflon connection | 2,000–5,000 PLN |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Calibration gas SO₂ | 7446-09-5 | Cylinder SO₂/N₂, 50–500 ppb, certified ±2% |
| Zero air | — | Synthetic air free of SO₂ (<0.5 ppb), from generator or cylinder |
Health and safety (OHS)
- SO₂ — toxic gas, respiratory irritant. Store cylinders in ventilated area.
- Pressure cylinders — use regulators and safety devices
- Monitoring station — ensure ventilation and gas detector
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN 14212:2013 — “Ambient air — Standard method for the measurement of the concentration of sulphur dioxide by ultraviolet fluorescence”.
How does this method work?
The air sample is drawn into the analyzer measurement chamber, where it is irradiated with UV radiation at ~214 nm wavelength. SO₂ molecules absorb UV radiation and transition to an excited state, from which they return to the ground state emitting fluorescence at longer wavelength (~330 nm).
What is the measuring range and accuracy?
Measurement range: 0–500 µg/m³ (typical), expandable to 2000 µg/m³; Detection limit: 0.5–2 µg/m³; Response time (T90): <120 s; 1h limit: 350 µg/m³ (not to exceed >24 times/year).
How long does the test take?
The times given for the individual stages add up to approximately 3 h 30 min. The procedure comprises 6 steps.
What equipment is required?
SO₂ analyzer (UV fluorescence), Gas calibrator (permeation or cylinders), Zero air generator (synthetic air), Sample intake system with probe. Indicative cost of the core instrument (SO₂ analyzer (UV fluorescence)): 30,000–60,000 PLN.
Where is this test used?
National Environmental Monitoring (GIOŚ/WIOŚ stations); Emission monitoring from coal power and heating plants; Urban air quality assessment; Monitoring protection zones around industrial plants; Early warning systems for air pollution.
What safety precautions apply?
SO₂ — toxic gas, respiratory irritant. Store cylinders in ventilated area.; Pressure cylinders — use regulators and safety devices; Monitoring station — ensure ventilation and gas detector.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN 14212.