Advanced radon exposure profile calculator

Use this calculator to estimate the combined annual effective dose from several radon-222 exposure scenarios. It is intended for a person who moves between locations, tasks or periods with different radon concentrations, occupancies or equilibrium factors.

Select whether the assessment is for a worker or a member of the public. The available calculation methods then change to the relevant ICRP options. For workers, the calculator can apply ICRP Publication 65, ICRP Publication 137 or compare the two. For members of the public, it can apply ICRP Publication 65, ICRP Publication 158 or compare the two.

Important: changing the assessed person or calculation method clears all exposure scenarios already entered. Choose these settings before entering a detailed profile.

Constructing an annual exposure profile

Add one row for each mutually exclusive location, task or period with a different concentration, equilibrium factor or occupancy. Every row is calculated separately and then added to produce one person’s combined annual result.

The combined duration of all scenarios must not exceed 8,760 hours/year. Do not enter overlapping periods or alternative exposure profiles in the same calculation, because all rows are added together. Calculate alternative profiles separately.

Concentrations can be entered in Bq/m³ or pCi/L. Where pCi/L is selected, values are converted internally using 1 pCi/L = 37 Bq/m³.

The suggested radon-222 equilibrium factor is F = 0.4. Each scenario can use a different value, but another value should only be used where it has been measured or professionally justified.

Breathing-rate sensitivity

For worker calculations using ICRP Publication 65 or the general ICRP Publication 137 method, the calculator can show a separate hypothetical linear breathing-rate sensitivity estimate. This is not a replacement for a full ICRP respiratory-tract assessment.

No separate breathing-rate multiplier is available for public calculations. It is also disabled for the ICRP Publication 137 substantial-activity or tourist-cave method because that coefficient already represents the specified exposure circumstance.

Scope: the calculator covers radon-222 and its short-lived progeny only. It does not calculate dose from radon-220 (thoron) or thoron progeny. Do not enter an uncorrected combined radon/thoron measurement.

Choose worker where the exposure arises from work. Choose member of the public for exposure in a home, school, public building or other non-occupational setting.

Important: Changing the assessed person or calculation method will clear all exposure scenarios already entered.
Choose the concentration unit for all exposure scenarios

All calculations are completed internally using Bq·m⁻³. Changing the unit converts any concentration values already entered.

Exposure scenarios

Add one scenario for each mutually exclusive location, task or period with a different radon concentration, equilibrium factor, occupancy or worker breathing-rate assumption. All rows are added together as one person’s annual exposure profile.

How the profile calculation works

For each exposure scenario, the calculator determines:

Radon exposure = radon-222 concentration × exposure time

The reference dose conversion factor for the selected method is stated at F = 0.4 and is adjusted for the equilibrium factor entered for that scenario:

Adjusted dose conversion factor = reference dose conversion factor × (scenario F ÷ 0.4)

The dose contribution from each scenario is:

Scenario dose = concentration × time × adjusted dose conversion factor

The combined result is the sum of the separate scenario doses:

Total effective dose = Σ scenario dose

Calculation methods

Worker — ICRP Publication 65

The reference dose conversion factor is 3.2 × 10⁻⁶ mSv per Bq·h·m⁻³ at F = 0.4.

Worker — ICRP Publication 137

The reference dose conversion factors at F = 0.4 are:

  • 6.7 × 10⁻⁶ mSv per Bq·h·m⁻³ for most workplace circumstances; and
  • 13.4 × 10⁻⁶ mSv per Bq·h·m⁻³ for substantial physical activity or tourist-cave work.

The higher coefficient should not be selected solely because a task includes some manual work. It is intended for specific circumstances involving substantial physical activity or tourist-cave work. Seek specialist advice where the appropriate category is uncertain.

Member of the public — ICRP Publication 65

The reference public dose conversion factor is 2.5 × 10⁻⁶ mSv per Bq·h·m⁻³ at F = 0.4.

Member of the public — ICRP Publication 158

The calculator uses the ICRP Publication 158 recommended public radon coefficient of 6.7 × 10⁻⁶ mSv per Bq·h·m⁻³ at F = 0.4, corresponding to 3 mSv per mJ·h·m⁻³.

Publication 158 presents age-specific dosimetric calculations but recommends the same rounded coefficient for public exposure in homes at all ages. The public route therefore does not apply a separate child coefficient or a user-selected breathing-rate multiplier.

Hypothetical worker breathing-rate sensitivity

Where enabled, the calculator displays the published-method result and a separate hypothetical linear sensitivity estimate:

Sensitivity estimate = standard dose × (selected breathing rate ÷ 1.2 m³·h⁻¹)

The comparison rate of 1.2 m³·h⁻¹ is the Reference Worker average during an 8-hour working day. This simple scaling does not reproduce the full ICRP respiratory-tract model and does not account separately for aerosol size, unattached progeny fraction, breathing route, airway deposition or clearance. It should be treated as an exploratory sensitivity calculation rather than a worker-specific dose assessment.

Workplace interpretation

If a representative annual-average concentration in an occupied workplace is above 300 Bq·m⁻³, the Ionising Radiations Regulations 2017 apply and the employer must notify HSE. An RPA with suitable radon experience should normally be consulted.

A short-term, task-period or occupancy-period concentration should not automatically be treated as the annual average. The calculated dose does not by itself determine whether IRR17 applies, whether an area requires designation or whether a worker requires classification.

Public-exposure interpretation

For members of the public, radon action and remediation decisions are normally based on representative annual-average concentration and the type of premises, rather than on the calculated dose alone. Where employees work in the same building, their occupational exposure should be assessed separately.

Potential alpha-energy exposure

The calculation details show equilibrium-equivalent exposure and potential alpha-energy exposure. A concentration of 1 Bq·m⁻³ of equilibrium-equivalent radon-222 corresponds to 5.56 × 10⁻⁶ mJ·m⁻³. The potential alpha-energy value is explanatory; the final dose is calculated using the selected ICRP dose conversion factor.

Radon-220 (thoron)

Radon-220 and its progeny are excluded. Thoron has a short half-life of approximately 56 seconds, so concentrations can vary sharply with distance from the emitting surface and the relationship between thoron gas and thoron progeny is highly location-dependent. The radon-222 default of F = 0.4 should not be applied to thoron.

Scope and limitations

This calculator provides an indicative effective-dose estimate based on the information entered. Its reliability depends on the concentrations, occupancies and equilibrium factors being representative and on the scenarios describing mutually exclusive periods in one person’s annual exposure profile.

It does not replace representative monitoring, a suitable and sufficient radiation risk assessment, formal dose assessment arrangements, professional remediation advice or advice from a suitable Radiation Protection Adviser.

References and calculation basis

 

Calculator version: 1.3
Calculation basis reviewed: July 2026