Consumer Glossary

Radon Measurement Technician
Inidividuals who have been trained and certified in the fundamentals of radon testing. This requires a basic understanding of radon and the health risks associated with it, as well as a thorough knowledge of measurement techniques and testing protocols.

National Radon Safety Board Certification as a Radon Measurement Technician requires:

  • Eight hours of classroom training on the nature of radon, radon entry in buildings, fundamental radon health risks, occupational health and safety, measurement devices and techniques,
    and current radon protocols;
  • Successful passing of examination based upon this knowledge;
  • Eight hours of continuing education biennially (i.e., four hours per year);
  • Adherence to the National Radon Safety Board Code of Ethics.

Measurement Technicians are qualified to place and retrieve measurement devices for the purpose of collecting radon data. This must be done in accordance with an active quality assurance program under the supervision of a certified Radon Measurement Specialist (RMS) or Accredited Radon Laboratory (ARL).

Radon Measurement Specialist
A Radon Measurement Specialist requires demonstration of knowledge which goes significantly beyond that required of a technician. In addition to basic training in the rudiments of radon measurements, the certified RMS must demonstrate a basic knowledge of radiation physics, an understanding of risk assessment, the epidemiological evidence of radon health risks, and the differences between various devices and techniques for measuring radon and radon decay products. The NRSB certified Radon Measurement Specialist must also understand the importance of radiation safety and be capable of designing and implementing a quality assurance program.
To be certified as an NRSB Radon Measurement Specialist a candidate must meet the following requirements:

  • Sixteen hours of classroom training on the nature of radon, radon entry in buildings, fundamental radon health risks, occupational health and safety, measurement devices and techniques, and current radon protocols;
  • Successful passing of a knowledge-based exam;
  • Sixteen hours of continuing education biennially (i.e., eight hours per year);
  • Adherence to the National Radon Safety Board Code of Ethics.

Radon Measurement Specialists are qualified to analyze — rather than simply report — radon measurements in a manner that is consistent with current knowledge.

Radon Mitigation Specialist
The NRSB requirements for certification as a Radon Mitigation Specialist (RRS) are essentially the same as those established by the Environmental Protection Agency Radon Proficiency Program for radon mitigators. To be certified a candidate must have a working knowledge of radon measurement techniques and health risks, and must demonstrate a broad knowledge in all aspects of residential radon mitigation.
The requirements for certification as a Radon Mitigation Specialist are:

  • Thirty-two hours of training, including not less than eight hours of hands-on experience;
  • Successful passing of a knowledge-based exam;
  • Sixteen hours of continuing education biennially (i.e., eight hours per year);
  • Adherence to the National Radon Safety Board Code of Ethics.

This includes the ability to evaluate the quality of radon measurements, assess alternative mitigation strategies, and properly design and install effective control systems.

Accredited Radon Laboratories
To be accredited by the National Radon Safety Board, laboratories will be required to demonstrate that they have thorough quality assurance programs (QAPs) and clearly defined standard operating procedures (SOPs).

Such QAPs and SOPs must cover all aspects of laboratory operations and must:

  • Establish appropriate education, training, and a radon safety program for all laboratory personnel;
  • Assure that all laboratory personnel adhere to the laboratory’s QAP;
  • Include blind tests and inter-comparisons with other NRSB accredited; laboratories, radon chambers, or federal laboratories must be conducted on a routine basis;
  • QAPs must include appropriate quality control measures including blanks, duplicates, and spikes, to determine the lower limits of detection, the precision, and accuracy of measurements.

Applicants must specify what devices the laboratory uses in performing radon analysis and list the NRSB device code for each on the application.

A laboratory must submit current proficiency test results for all devices used to perform radon analysis and for which the ARL wishes to maintain a proficiency listing – including activated charcoal, liquid scintillation, electret ion chamber, alpha track, continuous radon monitor and continuous working level monitor. To conduct a proficiency test, ARLs are required to submit the devices to an accredited secondary radon chamber for exposure to known concentrations. ARLs are expected to provide measurement results that are within + 25% of the target value.

An NRSB Radon Measurement Specialist (RMS) must be affiliated with the laboratory and listed on the application. Certification requirements for RMS are listed above.

Pending adoption of formal, detailed criteria for laboratory accreditation, the NRSB will accept applications for interim laboratory accreditation based upon state accreditation or listing by the United States Environmental Protection Agency (USEPA).

Accredited Radon Chambers
The purpose of accrediting radon chambers is to establish criteria to assure that measurement devices are capable of performing predictably under a wide range of environmental conditions. To do this a chamber must be able to consistently and reliably simulate conditions similar to those encountered in actual radon tests.

The basic criteria for chamber accreditation include:

  • Sufficient capacity to evaluate multiple instruments simultaneously;
  • Variable environmental controls capable of simulating and continuously monitoring a variety of environmental conditions, including temperature, humidity, ventilation and particulate concentrations;
  • Sources of pure RA-226 and Thoron traceable to an official standards laboratory;
  • Variable radon concentrations from 2 pCi/L – 50 pCi/L with radon progeny in the range of 0.0001 – 0.4 WL, traceable to an official agency; a variable equilibrium ratio of 0.3 – 0.7 is desirable;
  • Radiation standards must be strictly enforced to minimize occupational exposures;
  • Qualified chamber operators with a broad background and knowledge in instrument development, protocol use and a thorough grasp of QA and QC procedures;
  • A program of chamber inter-comparisons.

RADON GAS MEASUREMENT METHODS

For this method, an airtight container with activated charcoal is opened in the area to be sampled and radon in the air adsorbs onto the charcoal granules. At the end of the sampling period, the container is sealed and may be sent to a laboratory for analysis. The gamma decay from the radon adsorbed to the charcoal is counted on a scintillation detector and a calculation based on calibration information is used to calculate the radon concentration at the sample site. Charcoal adsorption detectors, depending on design, are deployed from 2 to 7 days. Because charcoal allows continual adsorption and desorption of radon, the method does not give a true integrated measurement over the exposure time. Use of a diffusion barrier over the charcoal reduces the effects of drafts and high humidity.

For this method, the detector is a small piece of special plastic or film inside a small container. Air being tested diffuses through a filter covering a hole in the container. When alpha particles from radon and its decay products strike the detector, they cause damage tracks. At the end of the test the container is sealed and returned to a laboratory for reading.

The plastic or film detector is treated to enhance the damage tracks and then the tracks over a predetermined area are counted using a microscope or optical reader. The number of tracks per area counted is used to calculate the radon concentration of the site tested. Exposure of alpha track detectors is usually 3 to 12 months, but because they are true integrating devices, alpha track detectors may be exposed for shorter lengths of time when they are measuring higher radon concentrations.

The unfiltered alpha track detector operates on the same principle as the alpha track detector, except that there is no filter present to remove radon decay products and other alpha particle emitters. Without a filter, the concentration of radon decay products decaying within the “striking range” of the detector depends on the equilibrium ratio of radon decay products to radon present in the area being tested, not simply the concentration of radon. Unfiltered detectors that use cellulose nitrate film exhibit an energy dependency that causes radon decay products that plate out on the detector not to be recorded.

This phenomenon lessens but does not totally compensate for the dependency of the calibration factor on equilibrium ratio. For this reason, EPA currently recommends that these devices not be used when the equilibrium fraction is less than 0.35 or greater than 0.60 without adjusting the calibration factor.

This method employs a small vial containing activated charcoal for sampling the radon. After an exposure period of 2 to 7 days (depending on design) the vial is sealed and returned to a laboratory for analysis. While the adsorption of radon onto the charcoal is the same as for the AC method, analysis is accomplished by treating the charcoal with a scintillation fluid, then analyzing the fluid using a scintillation counter. The radon concentration of the sample site is determined by converting from counts per minute.
This method category includes those devices that record real-time continuous measurements of radon gas. Air is either pumped or diffuses into a counting chamber. The counting chamber is typically a scintillation cell or ionization chamber. Scintillation counts are processed by electronics, and radon concentrations for predetermined intervals are stored in the instrument’s memory or transmitted directly to a printer.
For this method, an electrostatically charged disk detector (electret) is situated within a small container (ion chamber). During the measurement period, radon diffuses through a filter-covered opening in the chamber, where the ionization resulting from the decay of radon and its progeny reduces the voltage on the electret. A calibration factor relates the measured drop in voltage to the radon concentration. Variations in electret design determine whether detectors are appropriate for making long-term or short-term measurements. EL detectors may be deployed for 1 to 12 months. Since the electret-ion chambers are true integrating detectors, the EL type can be exposed at shorter intervals if radon levels are sufficiently high.
For this method, an electrostatically charged disk detector (electret) is situated within a small container (ion chamber). During the measurement period, radon diffuses through a filter-covered opening in the chamber, where the ionization resulting from the decay of radon and its progeny reduces the voltage on the electret. A calibration factor relates the measured drop in voltage to the radon concentration. Variations in electret design determine whether detectors are appropriate for making long-term or short-term measurements. ES detectors may be deployed for 2 to 7 days. Since electret-ion chambers are true integrating detectors, the ES type can be exposed at longer intervals if radon levels are sufficiently low.
This method requires a skilled technician to sample radon by using a pump or a fan to draw air through a cartridge filled with activated charcoal. Depending on the cartridge design and airflow, sampling takes from 15 minutes to 1 hour. After sampling, the cartridge is placed in a sealed container and taken to a laboratory where analysis is approximately the same as for the AC or LS methods.
This method uses a sample bag made of material impervious to radon. At the sample site, a skilled technician using a portable pump fills the bag with air, then transports it to the laboratory for analysis. Usually, the analysis method is to transfer air from the bag to a scintillation cell and perform analysis in the manner described for the grab radon/scintillation cell (GS) method below.
For this method, a skilled operator draws air through a filter to remove radon decay products into a scintillation cell either by opening a valve on a scintillation cell that has previously been evacuated using a vacuum pump or by drawing air through the cell until air inside the cell is in equilibrium with the air being sampled, then sealed. To analyze the air sample, the window end of the cell is placed on a photomultiplier tube to count the scintillations (light pulses) produced when alpha particles from radon decay strike the zinc sulfide coating on the inside of the cell. A calculation is made to convert the counts to radon concentrations.
For this method, a scintillation cell is fitted with a restrictor valve and a negative pressure gauge. Prior to deployment, the scintillation cell is evacuated. At the sample site, a skilled technician notes negative pressure reading and opens the valve. The flow through the valve is slow enough that it takes more than the 3-day sample period to fill the cell. At the end of the sample period, the technician closes the valve, notes the negative pressure gauge reading, and returns with the cell to the laboratory. Analysis procedures are approximately the same as for the GS method described above. A variation of this method involves use of the above valve on a rigid container requiring that the sampled air be transferred to a scintillation cell for analysis.
For this method, a sample bag impervious to radon is filled over a 24-hour period. This is usually accomplished by a pump “Programmed” to pump small amounts of air at predetermined intervals during the sampling period. After sampling, analysis procedures are similar to those for the GB method.
Consumer FAQs