Measurement of average annual value for radon in a home
If you have not previously measured radon levels in a home, you should always start by measuring the average annual value. The best way to do this is to set up radon detectors in the property for a period of 2-3 months during that part of the year when heating systems are on, which is normally from October to April. In order to obtain reliable and quality-assured measurement results, you should use radon detectors from an accredited laboratory, such as Radonova.
Reduce the risk of having to repeat the measurement
Irrespective of the type of measurement performed, it is important to follow the method description, for example when deciding where to position radon detectors. The best way to do this is to follow the instructions supplied with the radon detectors by the laboratory. This is particularly important when measuring radon levels in multi-occupancy buildings where the use of multiple radon detectors is recommended. In these situations it is very easy for detectors to go missing. By using multiple detectors you reduce the risk of having to repeat measurements, which can be a time-consuming process.
Radon instruments for use during inspections
If elevated radon levels have been confirmed in a home, it is important to identify the source of the radon before taking action to reduce levels. In the vast majority of cases, radon penetrates buildings from the ground in one way or another. The best instrument to use for an inspection is therefore a so-called radon sniffer that quickly and accurately identifies the point of radon entry. It is also important to be able to detect the gas as quickly as possible. In these situations you should not have to wait for equilibrium with the radon progeny that have a long half-life, such as polonium-214.
Consequently, what you need is a measurement instrument that rapidly detects radon. The most appropriate option in this case is an instrument with what is known as a pulsed ionisation chamber with energy resolution. A pulsed ionisation chamber enables the rapid detection of radon-222 (the radon level), i.e. as soon as the measurement chamber fills with ambient air, which takes about 2 minutes. The ATMOS radon sniffer is an excellent instrument for this application.
Right instruments ensure rapid results
Unlike measurement instruments that are based on semiconductor sensors, a major advantage of ATMOS is its rapid response time. This enables measurements to be recorded at several locations in a short space of time. Using ATMOS in connection with an inspection makes the work far more efficient. As radon can also be emitted by building materials, it is important during an inspection to be able to detect this source as well. The best instrument for this is a gamma meter.
Continuous radon measurement in a property
Continuous measurement is particularly useful in properties where an external source is suspected of causing a high radon level, i.e. in cases where there are problems with ground radon levels. For example, there is a greater risk of radon being present in properties built on sand and gravel. This is due to the high porosity of these soil types. Consequently, they contain large volumes of air that can easily transport radon up and into buildings.
Choose an instrument that can handle varied weather conditions
In this context it is important to understand what effect the weather is having on radon levels. The easiest way to do this is using an instrument that stores environmental parameters and radon levels in its internal memory for subsequent data analysis via a mobile app or using other software. An example of a suitable instrument is the RadonEye RD200 PLUS2.
If you also want to detect rapid changes, you will need an instrument with an active pump. Suitable instruments for this purpose are radon sniffers such as ATMOS and RAD7. These instruments are intended for professional use and are, as a rule, employed by radon consultants and various authorities. If a temporal resolution of less than one hour is required, then you need an active pump and a large measurement chamber.
Radon instruments for following up on measures
When action has been taken to reduce radon levels, it is important to check that those measures are actually having the intended effect. This should be done both by conducting new long-term measurement using dosimeters, and by monitoring the short-term effect. In connection with this you can also fine-tune the operation of radon extractors or ventilation systems (if used to reduce radon levels). In so doing, you can ensure that such equipment is operating at optimal efficiency in terms of reducing radon levels and energy consumption.
Important to understand variations and timelines
In cases where radon is present it is also important to study the effect of action taken using an instrument with a temporal resolution of 1-2 hours. This action, and saving a timeline of the variations in radon levels, makes it easier to analyse the situation and to select the correct ventilation options. A typical instrument intended for this purpose is the RadonEye RD200 PLUS2.
Measurement of ground radon in new-builds
To get an indication of the risk of high radon levels in new-builds, we recommend ground measurement. Please note, however, that it is not simply the case that low ground radon levels automatically mean low indoor levels (in the newly built property). It is frequently the building structure that has a greater impact on radon levels. However, it can be stated that there is an increased risk of elevated radon levels indoors if ground radon levels come back high.
In the case of new-builds, it can be wise to put in place preventive measures, such as a radon membrane, to avoid radon penetration. Large variations in ground radon levels are not normally seen over a 24-hour period; they tend to be more apparent over a period of weeks and months.
Instruments and methods should be able to withstand tough outdoor environments
Ground radon levels are most easily measured using instruments designed to detect ground radon. So-called instantaneous meters use a probe to collect soil air from a depth of 70-100 centimetres. There are also integrated methods that involve burying radon detector and leaving it to measure radon levels for a period of several days. The data collected is then analysed at a laboratory. It is important too to look at the “gamma index”. This is a weighted calculation of natural gamma radiation in the ground that originates from uranium, thorium and potassium. In order to perform this type of analysis, you need an instrument calibrated for direct contact with the ground. This instrument also needs to employ a spectroscopic algorithm capable of differentiating the concentration between these elements. An eminently suitable instrument for this application is MARKUS, which produces an almost instantaneous radon value with the correct permeability parameters for the analysed measurement depth.
Measurement of the average annual value for radon at a workplace
If you have not previously measured radon levels at a workplace, you should first start by measuring the average annual value for the workplace as a whole. A suitable method is long-term measurement using radon detectors from an accredited laboratory, such as Radonova. It is important that the entire workplace be included and that approved method descriptions are followed. This helps avoid setbacks caused by measuring levels throughout the workplace but not to a sufficient degree to be able to assess the risk of elevated levels.
Save time – get it right from the start
In order to avoid having to repeat the measurement process and to simplify any future inspection, we recommend establishing more measuring points than the minimum number suggested in the method description. This takes into account the risk of some radon detectors going missing during the measurement period, which is a very common occurrence.
If you want to play it completely safe, we recommend following the guidelines published by the International Radon Measurement Association (IRMA). The advantage of IRMA’s guidelines is that they establish an excellent procedure for measurement projects that helps reduce the time these take.
Radon instruments for workplace inspections
An inspection is necessary if it has been confirmed that there are elevated radon levels at a workplace. A map showing the differences in radon levels within the building is necessary in these cases in order to understand what action needs to be taken to reduce radon levels. This requires a thorough inspection. In order to investigate the cause of the elevated radon level, potential radon penetration should be studied. It is also important during the course of an inspection to investigate whether the building itself contains materials that can cause an elevated radon level.
Right instruments ensure rapid and reliable results
Suitable instruments for a complete inspection are the radon sniffer ATMOS and the gamma meter SGR. With ATMOS it is possible to detect >70% of the correct radon level within 5 minutes. Once measurements are complete in one location, it is possible to commence a new measurement within 15 minutes. This functionality requires the use of a pulsed ionisation chamber or a semiconductor detector with separation of polonium-218 and polonium-214. However, a pulsed ionisation chamber is the quicker option because it also measures radon-222, which is not possible with a semiconductor detector.
The SGR gamma meter features a large crystal that produces an immediate response to elevated gamma radiation levels. To obtain the correct measured value, SGR has also been calibrated for radon-226, which is another radon isotope. Countless instruments on the market have been calibrated for caesium-137, which produces an incorrect result.
Radon instruments for measurement during working hours
It may be necessary during the course of an inspection to study the timeline for radon levels in areas with elevated levels. As the average annual value is based on information about radon levels during both the day and night, it is important to understand what the radon levels are during working hours. In many cases, ventilation systems are switched off at night, which increases the risk of elevated radon levels during this period. However, when the ventilation is switched on during daytime hours, levels drop back down.
Immense value in understanding the differences
If it can be established that radon levels are below the limit value during working hours, this can be of immense value, because it is then possible to establish that employees are not being exposed to elevated levels. For this type of measurement, you can use a radon logger such as RadonEye RD200 PLUS2.
For applications where greater accuracy is required, we recommend a radon sniffer. Examples of such instruments are ATMOS and RAD7. For applications that require a high level of precision with a temporal resolution of 1 hour at a reference level of 200 Bq/m³, you need a measurement chamber with a large volume and the capacity to separate polonium-218 from polonium-214. This is, in turn, only possible using a radon sniffer of sufficient sensitivity to be able to spectrally separate polonium-218 from polonium-214.
Ventilation control with regard to radon
A common method of tackling elevated radon levels at a workplace is to control and regulate the ventilation system. Normally radon levels fall when there is more ventilation. An inspection is, however, always required before a final conclusion can be drawn. If this is an appropriate method to use, ventilation control can be a cost-effective solution that ensures not only a low radon level, but also minimal energy consumption.
The right sensor is important
One way to regulate radon levels with the aid of ventilation is to connect a radon sensor to the system. However, this requires the use of a sensor of sufficient accuracy to quickly signal when the radon level exceeds the reference level. A suitable sensor for this control function is the ROBIN radon sensor, which can be installed to control an existing ventilation system.
If it is necessary to remain in areas where there is an elevated radon level that cannot be remedied, you need to measure employees’ total exposure. This is achieved by calculating the cumulative exposure to radon levels, represented by the unit Bq-hours/cubic metre per year. To do this you need to measure radon levels at individual level on a quarterly basis using radon detectors and/or log radon activity at the workplace using a radon logger (RadonEye RD200 PLUS2).
The sensitivity and speed of the radon logger must be adapted to be able to separate working hours from non-working hours and to have a maximum uncertainty of ±20% for 48-hours’ measurement.
The individuals who remain on the premises in question, by law, also need to wear personal radon detectors continuously during working hours. The radon level that each employee is exposed to must be normally reported annually to the national radiation authority.
Authorities & Universities
Radon instruments for radon chambers
A radon chamber can be used for controlled exposure of radon detectors and for the calibration of radon instruments. In order to establish a stable level, you need a radon source that can be controlled by adjusting the airflow. The chamber also needs an airlock so that instruments can be placed inside the dosimeter without the level changing by more than 5%.
ATMOS have an integral pump that enable them to be connected to an external loop. This facilitates a rapid response to the concentration in the chamber without having to compensate for the diffusion time, which is the case if you have an instrument without an internal pump.
Radon instruments for surveys
Radon surveys of a site prior to the construction of a building are important for a number of reasons, including assessment of the need to produce an environmental impact study. It is vital that radon levels in existing buildings in the area also be included in the survey. If the indoor air of these buildings has not already been measured, the average annual value should be determined using dosimeters. By measuring ground radon levels and those in surrounding buildings, it is possible to better analyse the risk of an elevated radon level in the new-build.
MARKUS is an instantaneous meter that enables radon levels in soil air to be measured in just 10 minutes. The user adjusts the measuring depth by inserting the accompanying probe to a depth of between 70 and 100 centimetres.
Measurement of gamma radiation levels in soil
Ground measurement is commonly performed by geologists, who have received additional training in measurement of radon levels in soil and gamma radiation from the naturally occurring elements uranium-238, thorium-232 and potassium-40. In the case of rock/stone, the radon risk can be determined by measuring the gamma radiation present. This type of measurement requires sensitive instrumentation. The level of radiation is determined by measuring the dose rate and correlating it with expected radon risk.
A typical instrument for this application is SGR.
Gamma spectrometer helps distinguish radiation
One disadvantage of this instrument (SGR) is, however, that radium/uranium cannot be distinguished from, for example, residual caesium from the Chernobyl accident, which plays no part in the formation of radon. One way around this is to use a gamma spectrometer. This distinguishes the gamma radiation from the uranium series (U-238), the thorium series (Th-232) and radioactive potassium (K-40). In cases of elevated gamma radiation it is therefore useful to investigate the proportion of the uranium series and to determine the composition of the rock.
Gamma Surveyor Vario, with a suitable probe for the required accuracy and analysis time, is the ideal instrument in this situation.