Radon activity concentration and measurement duration.
A radon monitor measures activity concentration in a gas sample. The usual units are becquerels per cubic metre, Bq/m³, or picocuries per litre, pCi/L. One pCi/L corresponds to 37 Bq/m³. A result of 2 pCi/L therefore corresponds to 74 Bq/m³.
Indoor radon varies with building pressure, ventilation, soil-gas entry and weather. A short measurement describes its sampling period; estimating a longer-term exposure requires an appropriate measurement protocol. Report the start and end times, location, building conditions and uncertainty with the result.
Some instruments also distinguish thoron, a different radon isotope with a different decay chain and sampling behavior. Gas-phase radon concentration and airborne decay-product measurements are separate quantities. Select the instrument and protocol for the quantity required by the study.
Alpha detection and counting statistics.
Radon and its decay products emit alpha particles. Electronic monitors detect those events with a chamber and detector arrangement. Alpha spectrometry uses detected energy to distinguish contributions from particular decay products.
Corentium Pro uses passive diffusion into four chambers with silicon photodiodes. Durridge RAD8 uses electrostatic collection, a silicon detector and a pump-supported sample path. The latter provides distinct analysis modes and accessories for specialized sampling.
Precision depends on the number of detected events. In a simplified Poisson-counting example, 100 counts have an approximate counting standard deviation of 10 counts, or 10%; 400 counts have about 5% relative counting uncertainty. This excludes calibration, background and environmental contributions. A longer accumulation time improves statistics when the sample concentration is sufficiently stable.
Sampling and decay-chain behavior introduce additional response characteristics. A five-minute output interval cannot establish five-minute equilibration or adequate statistics at every concentration. The analysis mode and concentration must be included when interpreting a time series.
Radon measurement terminology.
- Activity concentration
- Radioactive decay activity per volume of sample.
- Alpha spectrometry
- Analysis of detected alpha-particle energies.
- Diffusion sampling
- Gas entry without a continuously pumped inlet.
- Counting uncertainty
- Statistical variability arising from the finite number of detected events.
- Background
- Counts that contribute to the signal in the absence of the intended sample activity.
- Thoron
- Radon-220, requiring isotope-aware analysis and sampling.
- Accumulation time
- Period used to collect events for a reported concentration.
Continuous electronic radon instruments.
Durridge's November 2025 RAD8 manual describes a development from its RAD7 instrument, with modes that retain access to energy spectra and counting data. Corentium Pro's manufacturer manual describes four parallel chambers, hourly storage and a professional reporting workflow.
Continuous records make time variation accessible, while the instrument and test protocol still determine how a result can be interpreted. A residential survey, mitigation assessment and laboratory radon experiment can require different sampling arrangements and documentation.
Radon manufacturer options.
Airthings Corentium Pro offers a compact passive instrument for indoor professional surveys. Durridge RAD8 supports pumped field and research measurements with mode-dependent analysis. Their sample paths, software and accessory requirements differ substantially.
Corentium Pro
- Technology
- Passive diffusion with four alpha-spectrometry chambers
- Measurement
- 0–100,000 Bq/m³; uncertainty depends on accumulation time
- Interface
- App and Pro Dashboard workflow; internal hourly records
- Consider for
- Professional indoor radon surveys
- Integration consideration
- Use horizontally, within documented conditions. Data export and integration depend on the current professional software workflow.
RAD8
- Technology
- Electrostatic collection and alpha spectrometry
- Measurement
- Radon and thoron analysis; mode-dependent counting sensitivity
- Interface
- Wi-Fi / USB and Capture software
- Consider for
- Pumped radon research and field measurements
- Integration consideration
- Accessories and sampling method determine air, soil-gas or water applications. Rapid and Precise modes have different response and statistics.
The Corentium manual gives different uncertainty specifications after 24 hours and seven days. RAD8 Rapid and Precise modes use different decay-product windows. Compare results with the actual mode, measurement duration and concentration retained.
Test protocols, calibration and data access.
Follow the measurement protocol applicable to the intended study and jurisdiction. Keep monitor placement, ventilation conditions and occupancy records consistent with that protocol. Corentium Pro's manual requires horizontal orientation and indoor operating conditions.
Pumped measurements need suitable tubing, flow and moisture handling. Water and soil-gas measurements require validated accessories and procedures; an air instrument's displayed units do not establish those methods automatically. Investigate background and recovery after high exposure before reusing an instrument for a low-level sample.
Maintain calibration certificates and scheduled service. Durridge recommends annual RAD8 recalibration in the cited manual. Professional reporting may impose additional requirements. Store uncertainty, timestamps, serial number, mode and any interruptions with exported results.
Confirm the current software workflow and export format before choosing a platform connection. App synchronization, USB export and a documented real-time protocol provide different integration routes. Installed cost includes calibration, accessories, software features and field service. No direct industrial gateway interface is established solely by the presence of a USB port.
Radon monitoring questions.
Why is a longer measurement usually more precise?
It collects more decay events, reducing relative counting uncertainty. Changing concentration, background and calibration still contribute to the total uncertainty.
Can an indoor monitor measure radon in water directly?
A water measurement requires an appropriate sampling method, accessory and conversion procedure. The instruments compared here detect activity in their gas chambers.
Does an hourly record represent a long-term building average?
It describes the instrument's reporting interval. A representative long-term result requires a suitable test duration and building protocol.
Read the original documentation.
Specifications use the linked manufacturer documents and their stated revisions. Review the current datasheet and exact ordered variant before final specification. Comparisons use manufacturer specifications and technical documentation.