🌿 Radon measurement in buildings
In short
Measurement of average radon (²²²Rn) concentration in indoor air of buildings using passive detectors (alpha tracks). The test is performed according to PN-EN ISO 11665-4:2020, PN-EN ISO 11665-8:2020; Measurement range: 20–10,000 Bq/m³. The procedure comprises 6 steps (about 7 h 50 min in total); it is used for: Radon measurement in residential and public buildings, Testing buildings in radon zones (Sudetes, Kraków-Częstochowa Jura), Radon control in workplaces (mines, caves, basements).
At a glance
- Standard: PN-EN ISO 11665-4:2020, PN-EN ISO 11665-8:2020
- Category: Environmental
- Procedure steps: 6
- Total time of stages: 7 h 50 min
- Measurement range: 20–10,000 Bq/m³
- Detection limit: 20 Bq/m³ (at 3 months exposure)
- Reference level (EU): 300 Bq/m³ (existing buildings)
Overview
Radon-222 is a natural radioactive noble gas, a decay product of radium-226 in the Earth's crust. Radon penetrates buildings through foundation cracks, pipes, and fractures, accumulating in basements and ground floors. It is the second (after smoking) cause of lung cancer — WHO estimates 3–14% of lung cancer deaths are due to radon.
EURATOM Directive 2013/59 establishes a reference level of 300 Bq/m³ for existing buildings. In Poland, radon measurements are regulated by Atomic Law and regulations of the President of PAA. Measurement is performed with passive CR-39 type detectors (alpha track detectors) exposed for 2–12 months to obtain reliable average concentration.
Method principle
A passive detector (CR-39 film in diffusion housing) is exposed in a room for 2–12 months. Alpha particles emitted by radon and its progeny (²¹⁸Po, ²¹⁴Po) leave microscopic tracks in the CR-39 film. After exposure, the film is etched in NaOH (6 mol/L, 90°C, 6 h), which enlarges the tracks to sizes visible under microscope. The number of tracks per cm² is proportional to radon concentration × exposure time. Concentration is calculated from calibration (detector calibration factor).
Applications
- Radon measurement in residential and public buildings
- Testing buildings in radon zones (Sudetes, Kraków-Częstochowa Jura)
- Radon control in workplaces (mines, caves, basements)
- Assessment of anti-radon remediation effectiveness
- Testing for real estate transactions
Key parameters
| Parameter | Value |
|---|---|
| Measurement range | 20–10,000 Bq/m³ |
| Detection limit | 20 Bq/m³ (at 3 months exposure) |
| Reference level (EU) | 300 Bq/m³ (existing buildings) |
| Exposure time | 2–12 months (recommended ≥3 months) |
| Measurement uncertainty | ±15–25% (at concentration >100 Bq/m³) |
Standard
- Standard number
- PN-EN ISO 11665-4:2020, PN-EN ISO 11665-8:2020
- Title (PL)
- Pomiary promieniotwórczości w środowisku — Powietrze: radon-222 — Część 4: Zintegrowana metoda pomiaru średniego stężenia aktywności z użyciem pasywnych próbników
- Title (EN)
- Measurement of radioactivity in the environment — Air: radon-222 — Part 4: Integrated measurement method for determining average activity concentration using passive sampling
Step-by-step procedure
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Detector placement
Place 2 detectors on lowest occupied floor (bedroom, living room). Height 0.5–2 m, away from windows and ventilation.
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Exposure
Leave detectors for 3–12 months. Record start and end dates with 1-day accuracy.
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Detector retrieval
Close detectors in housing and send to analytical laboratory.
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Chemical etching
CR-39 film etched in 6 mol/L NaOH, 90°C, 6 h. After etching rinse in distilled water and dry.
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Track counting
Count alpha tracks under microscope (automatically or manually). Typically 3–10 fields of view per detector.
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Concentration calculation
C [Bq/m³] = (track density − background) / (calibration factor × exposure time). Result as annual average concentration.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| CR-39 passive detectors | Radosys RS Radon, NRPB/PHE Track-etch, Gammadata Rapidos | 30–80 PLN/pc. |
| Etching-counting system | Radosys RSV-8, TASL Radometer (automatic) | 50,000–150,000 PLN |
| Water bath with thermostat | 90°C ± 1°C, for CR-39 etching | 3,000–8,000 PLN |
| Microscope with automatic counting | Olympus BX53 with camera + software | 30,000–80,000 PLN |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Sodium hydroxide NaOH | 1310-73-2 | 6 mol/L solution (240 g/L) for CR-39 etching |
| Distilled water | — | For film rinsing after etching |
Health and safety (OHS)
- NaOH 6 mol/L — highly corrosive. Acid-resistant gloves, goggles, apron.
- 90°C bath — burn risk. Thermal gloves.
- Radon — radioactive, but detectors pose no hazard
- NaOH waste — neutralize before disposal
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN ISO 11665-4:2020, PN-EN ISO 11665-8:2020 — “Measurement of radioactivity in the environment — Air: radon-222 — Part 4: Integrated measurement method for determining average activity concentration using passive sampling”.
How does this method work?
A passive detector (CR-39 film in diffusion housing) is exposed in a room for 2–12 months. Alpha particles emitted by radon and its progeny (²¹⁸Po, ²¹⁴Po) leave microscopic tracks in the CR-39 film.
What is the measuring range and accuracy?
Measurement range: 20–10,000 Bq/m³; Detection limit: 20 Bq/m³ (at 3 months exposure); Reference level (EU): 300 Bq/m³ (existing buildings); Exposure time: 2–12 months (recommended ≥3 months).
How long does the test take?
The times given for the individual stages add up to approximately 7 h 50 min. The procedure comprises 6 steps.
What equipment is required?
CR-39 passive detectors, Etching-counting system, Water bath with thermostat, Microscope with automatic counting. Indicative cost of the core instrument (CR-39 passive detectors): 30–80 PLN/pc.
Where is this test used?
Radon measurement in residential and public buildings; Testing buildings in radon zones (Sudetes, Kraków-Częstochowa Jura); Radon control in workplaces (mines, caves, basements); Assessment of anti-radon remediation effectiveness; Testing for real estate transactions.
What safety precautions apply?
NaOH 6 mol/L — highly corrosive. Acid-resistant gloves, goggles, apron.; 90°C bath — burn risk. Thermal gloves.; Radon — radioactive, but detectors pose no hazard; NaOH waste — neutralize before disposal.
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 ISO 11665-4/-8.