Inputs
Enter a measured radon level, choose a dose convention, and set your occupancy. The calculator estimates dose from radon progeny using an equilibrium factor.
Formula Used
This calculator estimates effective dose from radon progeny using an equilibrium equivalent concentration (EEC):
Exposure = EEC × t
Dose (mSv/y) = Exposure × DCF / 1,000,000
C is radon concentration in Bq/m³, F is the equilibrium factor, t is occupancy hours per year, and DCF is in nSv per (Bq·h·m−3) of EEC. WLM is also computed using 1 WL = 3700 Bq/m³ (EEC) and 1 WLM = 170 h at 1 WL.
How to Use This Calculator
- Enter your measured radon concentration and choose the unit.
- Set the equilibrium factor F if you have local ventilation data.
- Enter annual occupancy hours for the space being assessed.
- Select a dose convention or provide a custom coefficient.
- Press Calculate to view dose, WLM, and detailed steps.
- Use the download buttons to export your results.
Example Data Table
| Scenario | Radon (Bq/m³) | F | Hours/year | DCF (nSv/EEC) | Dose (mSv/y) |
|---|---|---|---|---|---|
| Well‑ventilated office | 80 | 0.30 | 2,000 | 9 | 0.4320 |
| Typical home average | 100 | 0.40 | 7,000 | 9 | 2.5200 |
| Basement room frequent use | 200 | 0.40 | 3,000 | 9 | 2.1600 |
| High level dwelling | 300 | 0.40 | 7,000 | 9 | 7.5600 |
Examples are illustrative and assume the UNSCEAR 9 nSv coefficient.
Radon Inhalation Dose Estimation Guide
1) Why indoor radon matters
Radon is a naturally occurring radioactive gas that can accumulate indoors, especially in lower levels and poorly ventilated rooms. Long‑term exposure increases lung cancer risk, so practical dose estimates help prioritize testing, ventilation improvements, and mitigation decisions for the spaces where people spend the most time.
2) Concentration units and conversions
Measurements are commonly reported as Bq/m³ (SI) or pCi/L (US). This calculator converts pCi/L to Bq/m³ using 1 pCi/L = 37 Bq/m³, so readings from different reports can be compared on a single scale. Using a long‑term average reduces seasonal and daily variability.
3) Equilibrium factor and progeny impact
Health impact is driven mainly by short‑lived radon progeny. The equilibrium factor F represents how much progeny is present relative to radon gas. Indoors, a typical planning value is F ≈ 0.4, but it can shift with aerosol levels, ventilation rate, filtration, and occupancy patterns.
4) Occupancy time turns levels into exposure
Concentration alone is not exposure. Exposure is computed as EEC × time, where EEC = C × F. For context, full‑time residence can be near 7,000 hours/year, while many offices may be near 2,000 hours/year. The same radon level can produce very different annual doses across these scenarios.
5) Dose conversion coefficient selection
The calculator supports a 9 nSv per (Bq·h·m−3) EEC convention and a 16 nSv option, plus a custom coefficient. Different conventions reflect different epidemiological assumptions and dosimetric models. Selecting a coefficient consistently across assessments helps maintain comparability when tracking improvements over time.
6) Interpreting WLM, WL, and cross‑checks
Working Level (WL) and Working Level Month (WLM) are legacy exposure quantities used in radon protection. Here, WL is derived from EEC using 1 WL = 3700 Bq/m³ EEC, and WLM uses 170 hours at 1 WL. The calculator also cross‑checks dose from WLM using the implied mSv/WLM for your chosen coefficient.
7) Data‑driven mitigation planning
Use dose estimates to rank spaces for action. If a basement room shows higher dose than living areas, focus mitigation there first: improve ventilation, seal entry routes, manage pressure differences, and consider sub‑slab depressurization where appropriate. Retest after changes and compare results using identical input assumptions.
8) Good practice and reporting tips
Document the measurement method, sampling duration, season, and room location. Record occupancy assumptions and the selected dose coefficient, then export results to CSV or PDF for audit trails. When multiple zones exist, compute each zone separately and summarize building‑wide exposure as an occupancy‑weighted average.
This content supports planning and comparison. For regulatory decisions, follow your local radon guidance and measurement standards.
FAQs
1) What inputs most strongly affect the dose?
The dose scales linearly with radon concentration, equilibrium factor, occupancy hours, and the selected dose coefficient. Doubling any one of these inputs doubles the estimated annual dose, all else being equal.
2) Should I use short‑term or long‑term radon results?
Use long‑term averages whenever possible because radon varies by season and weather. If only short‑term data exist, treat the estimate as preliminary and update it after a longer measurement period.
3) What equilibrium factor should I choose?
A common indoor planning value is 0.4. If you have site measurements or strong ventilation/filtration differences, adjust F accordingly. Higher aerosol and lower ventilation can increase F, raising dose at the same radon level.
4) Why are there different dose coefficients?
Coefficients represent different model assumptions and epidemiological interpretations for converting exposure to effective dose. Choose one convention consistently for comparisons, or use a custom value when your program specifies a particular factor.
5) What do WL and WLM mean in this report?
WL is a concentration‑based exposure quantity tied to radon progeny, and WLM combines WL with time. This calculator derives WL from EEC and converts time to WLM using 170 hours per month of exposure.
6) How can I reduce radon dose effectively?
Improve ventilation, seal obvious entry pathways, and manage building pressure relative to soil. For persistently high levels, sub‑slab depressurization is commonly used. Retest after mitigation and re‑estimate dose using the same assumptions.
7) Does this replace professional health or regulatory advice?
No. It is a planning calculator for comparing scenarios and documenting assumptions. For compliance, mitigation design, or medical questions, follow local radon authorities, certified testers, and healthcare professionals.