Radon chamber: what it is, how it works and why it is essential for calibrating measurement instruments
When people talk about radon measurement, attention is often focused on the instrument: the detector, monitor, sensor or device used to measure radon concentration in an environment.
But to know whether an instrument measures reliably, something more is needed: a system capable of generating controlled, repeatable and technically verifiable conditions.
This system is the radon chamber.
A radon chamber is a controlled environment in which a defined concentration of radon-222 can be generated, monitored over time and used to verify the response of measurement instruments.
In other words, it is the heart of a radon instrument calibration laboratory.
In this article, we explain what a radon chamber is, how it works, which parameters need to be controlled and how we at RadonStar use our chamber to calibrate radon measurement instruments.
What is a radon chamber?
A radon chamber is a system designed to produce and maintain a controlled atmosphere containing radon, usually radon-222.
Its purpose is not simply to reproduce a generic indoor environment, but to create known, monitored and documented technical conditions. Instruments to be calibrated are placed in these conditions so that their response can be compared with a reference.
A radon chamber therefore helps answer one fundamental question:
Does the instrument measure radon consistently when exposed to a known and controlled concentration?
To answer this question, the chamber must allow several elements to be controlled or monitored:
- radon-222 activity concentration;
- exposure time;
- temperature;
- relative humidity;
- pressure;
- external environmental conditions;
- homogeneity of the internal atmosphere;
- instrument behaviour during the test.
Without a controlled environment, it would be very difficult to technically assess the response of a radon instrument.
Why is a radon chamber needed for calibration?
A radon measurement instrument provides a value, usually expressed in Bq/m³. However, to understand whether that value is reliable, it must be compared with a known situation.
This is exactly what a radon chamber is used for: creating a reference atmosphere.
During calibration, the instrument is exposed to a controlled radon concentration. Its reading is then compared with the reference value measured or determined by the laboratory system.
This comparison makes it possible to evaluate:
- whether the instrument responds correctly;
- whether there is a deviation from the reference;
- whether the response is compatible with the intended use;
- whether the instrument maintains adequate performance over time;
- whether the result should be documented in the calibration report.
The radon chamber is therefore essential because it turns a generic check into a controlled technical test.
A radon chamber is not just a container
A common misconception is to imagine a radon chamber as a simple closed container into which radon is introduced.
In reality, a radon calibration chamber is a much more complex system.
It must be designed to generate, control, monitor and manage a radon-containing atmosphere safely and repeatably.
Such a system may include:
- an exposure chamber or volume;
- a radon source;
- a control system;
- valves, pumps and gas management circuits;
- reference instruments;
- environmental sensors;
- ventilation or mixing systems;
- discharge procedures;
- safety systems;
- software or devices for data recording.
All these elements work together to create the conditions required for calibration.
The role of radon-222 concentration
Radon-222 is the radon isotope most relevant to indoor radon measurement and exposure assessment in enclosed environments.
In a calibration chamber, the radon-222 concentration must be generated and controlled so that instruments can be exposed to known conditions.
During the test, it is not enough to simply “put radon” into the chamber. It is necessary to know how the concentration changes over time, how it is distributed inside the volume and how it behaves in relation to environmental parameters.
For this reason, concentration control is one of the most delicate aspects of a radon chamber.
A good chamber should make it possible to:
- reach the target concentration level;
- maintain the concentration under controlled conditions;
- monitor its trend over time;
- document the values used during the test;
- discharge the gas safely at the end of the session.
Why are temperature, humidity and pressure important?
Radon measurement instruments can be affected by environmental conditions.
Temperature, humidity and pressure may influence instrument behaviour, sensor response and test stability.
For this reason, a radon chamber must allow environmental parameters to be controlled or at least monitored.
The most important parameters include:
Temperature
Temperature may affect the electronic and physical behaviour of some instruments.
Relative humidity
Humidity is particularly important because it can influence the response of certain detectors and the management of the internal atmosphere.
Pressure
Pressure may affect gas conditions and the overall evaluation of the test.
Ambient gamma dose
Monitoring the ambient gamma background is useful for documenting the radiometric context of the test.
These parameters are not secondary details. They are part of calibration quality and help correctly interpret the results.
The importance of homogeneity inside the radon chamber
Another key aspect is the homogeneity of the internal atmosphere.
If the radon concentration is not evenly distributed, two instruments placed in different positions inside the chamber may be exposed to different conditions.
This would reduce the reliability of the comparison.
For this reason, many radon chambers use mixing, ventilation or recirculation systems to make the internal atmosphere more uniform.
The goal is to ensure that the instruments placed inside the chamber are exposed to conditions that are as consistent and representative as possible.
What is a STAR system?
In radiation protection instrumentation, chambers and systems used to create radon test atmospheres are often linked to the concept of STAR, which stands for System for Test Atmospheres with Radon.
A STAR system is designed to create reference atmospheres containing radon and, in some cases, its decay products.
This type of system is used to test, verify and calibrate instruments that measure radon or its progeny.
The radon chamber is therefore a central part of a broader system: not only the physical volume where the gas is introduced, but the entire set of components, controls, references and procedures that make the test possible.
The RadonStar radon chamber
The RadonStar laboratory was designed for calibrating instruments that measure radon activity concentration.
Our radon chamber makes it possible to create a reference atmosphere containing radon-222 and expose instruments to controlled conditions.
The goal is to verify instrument response, document the results and provide the customer with a calibration report useful for the technical management of their device.
The RadonStar laboratory uses an internally developed approach designed to improve the control of radon concentration inside the chamber and make calibration sessions more efficient to manage.
The RadonStar HYBRID MODE method
One of the distinctive elements of the RadonStar laboratory is the HYBRID MODE method.
This method was developed to combine the advantages of traditional configurations while reducing some operational limitations.
Its purpose is to make it easier to control variations in radon-222 activity concentration inside the calibration chamber.
In radon calibration, concentration control is not a secondary detail. It is one of the factors that determine the quality of the test.
Being able to effectively manage the increase, maintenance and discharge of radon concentration makes it possible to organise more controlled and better documented sessions.
The RadonStar control system
The RadonStar radon chamber is managed through a control system developed to automate the main phases of the process.
The system includes components such as a control panel, solenoid valves, pumps, digital switches and a microcontroller.
Thanks to this system, the laboratory can:
- start a calibration programme;
- control radon concentration;
- maintain the target concentration;
- increase it when necessary;
- discharge the gas at the end of the test;
- monitor the progress of the session;
- record data useful for the calibration report.
Automation does not replace the laboratory’s technical control, but it supports it. It helps manage the operational phases of calibration in a more organised and repeatable way.
The radon source
A radon source is required to generate the reference atmosphere.
The RadonStar laboratory uses a certified radon source to generate radon-222 concentration inside the chamber.
The source is one of the fundamental elements of the system because it makes it possible to produce the atmosphere on which the calibration test is based.
Source management must be integrated with the control system, reference instruments and safety procedures.
The reference instrument
During calibration, the customer’s instruments are compared with a reference.
In the RadonStar laboratory, metrological traceability is supported by the use of a reference instrument for real-time radon measurement.
The reference instrument is itself periodically calibrated by European institutes certified according to ISO/IEC 17025.
This step is important because calibration quality also depends on the quality and metrological management of the reference used.
In practice, having a controlled chamber is not enough: a reliable reference is also needed to compare the response of the instruments.
The zero-radon atmosphere
In the calibration process, it is also important to check instrument behaviour in the absence of radon or under controlled background conditions.
For this reason, RadonStar also uses a special chamber with a nitrogen atmosphere, dedicated to background checks of instruments.
This phase is useful for checking the instrument response when it is not exposed to a significant radon concentration.
Background control is particularly important because it helps correctly interpret instrument behaviour during subsequent exposure in the radon chamber.
Why RadonStar uses a climatic chamber
One distinctive aspect of the RadonStar system is the use of a climatic chamber to create the radon-222 reference atmosphere.
Using a climatic chamber instead of a simple container makes it possible to better control, monitor and manage environmental parameters during the test.
RadonStar currently controls temperature and average radon-222 activity concentration, while constantly monitoring humidity, relative pressure and ambient gamma dose.
This approach makes it possible to better document the test conditions and manage calibration in a more structured way.
How we use the radon chamber to calibrate instruments
The RadonStar calibration process can be described in several simplified steps.
1. Receiving and identifying the instrument
When the instrument arrives at the laboratory, it is identified and associated with the booked calibration session.
Model, serial number and all information needed for proper test management are checked.
2. Preliminary check
Before exposure, the instrument may undergo preliminary checks, including verification of background behaviour.
This phase helps assess the initial condition of the device.
3. Chamber preparation
The chamber is prepared for the calibration session. The control system manages the components required to create the internal atmosphere.
Environmental parameters are monitored and the required test conditions are prepared.
4. Generation of the reference atmosphere
The system generates an atmosphere containing radon-222, with controlled and monitored concentration.
During this phase, the reference instrument measures the concentration trend.
5. Instrument exposure
The instruments to be calibrated are exposed to the reference atmosphere for the time planned in the session.
During exposure, the laboratory monitors the test conditions and records the necessary data.
6. Comparison with the reference
The instrument response is compared with the reference value.
This comparison makes it possible to evaluate the instrument deviation and describe its behaviour under the test conditions.
7. Discharge and safety management
At the end of the session, the system manages radon discharge in a controlled way.
This phase is an integral part of laboratory safety and efficiency.
8. Issuing the calibration report
The results are included in the calibration report, which is sent to the customer.
The report documents the instrument, test conditions, results obtained and the technical information needed to interpret the calibration.
Which instruments can be calibrated in a radon chamber?
A radon chamber can be used to check different types of instruments, depending on the characteristics of the laboratory and the procedures applied.
In the case of RadonStar, sessions are organised for specific categories of instruments, including:
- Corentium Pro / Corentium Plus;
- RadonEye / RadonEye Plus2;
- EcoQube;
- other instruments that may be evaluated through a special request.
Session-based organisation makes it possible to plan laboratory activities in an orderly way and offer customers dedicated time windows for calibrating their instruments.
Why the radon chamber matters for professionals
For professionals who measure radon, instrument quality is part of service quality.
A measurement performed with an unchecked instrument may be difficult to support, especially when the data is used for technical decisions, company documentation or remediation work.
Calibration in a radon chamber helps strengthen the credibility of the data because it shows that the instrument has been verified under controlled conditions.
This is particularly important for:
- technicians performing radon measurements;
- companies monitoring workplaces;
- environmental consultants;
- laboratories;
- radon mitigation operators;
- sellers and rental providers of instruments;
- organisations managing multiple devices.
A calibrated instrument communicates seriousness, technical care and responsibility.
Radon chamber and measurement reliability
A radon chamber does not eliminate measurement uncertainty. No calibration does.
Its value lies in making uncertainty better known, documented and manageable.
Through a test in a controlled atmosphere, the laboratory can evaluate how the instrument responds compared with a reference. This allows the customer to better understand their device and use it with greater awareness.
Calibration is therefore not a mere formality. It is a quality control tool.
Frequently asked questions about radon chambers
Is a radon chamber dangerous?
A radon chamber contains a radioactive gas, so it must be designed and managed according to safety criteria. In specialised laboratories, radon is generated, controlled and discharged according to specific technical procedures.
Is a radon chamber only used for professional instruments?
It is particularly important for instruments used in professional contexts, but it can also be useful for devices used in situations where greater data reliability is required.
What is the difference between a radon chamber and a real environment?
A real environment has variable conditions that cannot always be controlled. A radon chamber, on the other hand, makes it possible to create known and monitored conditions that are useful for verifying instrument response.
Why is it important to control temperature and humidity?
Because environmental conditions can influence the behaviour of some instruments. Monitoring these parameters helps interpret calibration results more correctly.
Does the radon chamber adjust the instrument?
No. The chamber exposes the instrument to a controlled atmosphere. Calibration evaluates the response of the instrument, but it does not necessarily involve automatic adjustment of the device.
Can I request calibration for an instrument that is not listed in the calendar?
Yes. If the instrument is not included in the standard sessions, you can submit a special calibration request. RadonStar will assess whether it can be included in a dedicated or compatible session.
Conclusion: the radon chamber is the heart of calibration
A radon chamber is much more than a container.
It is a technical system designed to generate a controlled radon-222 atmosphere, monitor environmental parameters, compare instruments with a reference and document their behaviour.
For this reason, it is the heart of a radon instrument calibration laboratory.
At RadonStar, we use our radon chamber to provide a structured, controlled and documented calibration service, designed for professionals who use radon instruments and want to increase the reliability of their measurements.
Do you need to calibrate your radon instrument?
Check the RadonStar session calendar and choose the most suitable time window for your device.