Radon Testing
Radon is a naturally occurring radioactive soil gas, which is produced by the breakdown of Uranium in soil, rock, and water. Radon is the second leading cause of lung cancer deaths in the USA and Canada after smoking and it accounts for approximately 3200 deaths per year in Canada alone. Radon is the largest single source of radiation in the world, accounting for approximately 42% globally. By comparison, the nuclear industry accounts for approximately 1%.
Radon is present in all areas of the world at varying concentrations. Radon potential maps cannot be relied upon to determine what buildings may be affected by Radon. Radon is colourless and odourless and cannot be detected in a building without testing.
Radon is a noble gas, which means it is not chemically reactive. It passes through most filters but will adsorb to charcoal. It is carcinogenic and will cause lung cancer. Radon is heavier than air and therefore tends to sink, so the highest concentrations within a building are generally in the lowest level of the building.
When Radon is breathed into the lungs, it tends to stay trapped inside, bouncing around and striking the lung cells and sticking to the lung tissue. This can cause physical or chemical damage to the DNA, which can then lead to lung cancer.
Radon can enter homes in many ways such as cracks in floor slabs and foundations, sump pits, floor drains, basement windows, building penetrations, potable wells, showers, plumbing fixtures and more. Buildings which are negatively pressurized compared to the soils below and surrounding the foundation cause more radon infiltration. This pressure differential will naturally draw more Radon gas into a building through the various entry routes outlined above. This is the primary reason why Radon concentrations vary so much from building to building. How a building is constructed, pressurized and potential entry points vary greatly from building to building, even those which are neighbouring one another. There is no way to predict what the concentrations will be within a building without testing.
The winter season is the optimal time to test a building. Radon concentrations will vary within a building hour to hour, day to day and month to month. It is dependent on many factors such as wind direction, weather (snow cover or ongoing rain will bias results), season, time of day and much more. Concentrations are generally the highest in the winter months when a building is sealed tighter (doors/windows closed), the HVAC system operates more to continually heat a building, stack effect is more of a factor (warm air rises in a building and therefore draws more soil gas in from around foundation), and snow cover prevents Radon from coming up through the ground as it normally does and instead directs it towards a basement floor or foundation.
In Canada, Radon is measured in the unit Becquerels (Bq) and concentrations are expressed as Bq/m3 (1 m3 = 1000 L of air). The maximum allowable concentration within a building is 200 Bq/m3 . For general reference, the average indoor Radon concentration in Canada is around 45 Bq/m3 and the average outdoor concentration is around 10 Bq/m3 .
An indoor test should be taken over a term of at least 3 months (91 days) and up to one year. This ensures more accurate results as concentrations can vary greatly in the shorter term and results are therefore less reliable. Shorter term tests are sometimes done (schools, real estate transactions, etc.) but should be followed up with long term testing. Only long term testing results can determine if Radon mitigation within a building is required. Testing should ideally be done in the winter months if possible when concentrations are generally highest. The test should be done in the lowest area of a building that is occupied for at least 4 hours a day by building occupants. For example, if a basement is only used for storage and very rarely entered, it is more meaningful to collect a sample on the mainfloor.
Many types of devices are available to test Radon in a building. Some are better for longer term tests such as the Electret Ion Chamber (EIC) or E-PERM and the alpha track detectors (can be used for shorter term tests also). Activated charcoal devices such as open face, diffusion barrier or bags/vials are an option for shorter term tests but are less reliable. Continuous Radon monitors use computers and are an ongoing direct read instrument. These are typically used more often for shorter term tests but can be used for longer term as well. Digital detectors that can be plugged into a wall similar to a CO detectors are available on the market but cannot be used as a professional measurement device as they are not accurate enough. Continuous working level monitors are also available, but are more typically used in research studies and the mining/nuclear industry.
Radon needs to be mitigated when concentrations in a building exceed 200 Bq/m3 . This must be measured by a long term test of at least 3 months. If the concentration is between 200 – 600 Bq/m3 , you have within 2 years to mitigate the building. This range of elevated concentration within a building is found in approximately 6.7% of Canadian homes (around 1 in 15). If the concentration is found to be greater than 600 Bq/m3 , you have 1 year to mitigate the building. This range of elevated concentration within a building is found in only approximately 0.7% of Canadian homes.
Many methods of Radon mitigation are available. The most common and most effective overall is active sub-slab depressurization. This involves having a pipe installed through the basement floor slab into the granular fill below. A series of pipes is connected to exhaust to the exterior. A fan is connected to draw air from below the floor slab and around the foundation and exhaust it out the piping so it doesn’t enter the building. Sump hole and drainage system depressurization are also options and are different variations of sub-slab depressurization, only the point where the suction is placed is different. For buildings with soil crawlspaces, active sub-membrane depressurization is very effective. This involves covering the exposed soils with a thick plastic (polyethylene) membrane and building an air tight seal to the foundation walls. The pipe and fan system is then installed to collect Radon gas and exhaust it outdoors.
When mitigating, it is critical to evaluate the pressure differentials within a building, which is a main contributor to Radon entering into buildings. It is also important to seal and repair major entry routes such as sump pits, floor drains, cracks in poured foundation walls and floor slabs, floor/wall joints at base of wall, voids in concrete block walls etc. Increasing mechanical ventilation in homes can balance pressures and help to reduce indoor Radon concentrations. This can be achieved with HRVs and ERVs.
Radon testing and mitigation will be on the rise in the years to come. Health Canada has guidelines for testing within a home or in a public building. All consultants and contractors assessing or mitigating a building with Radon need to be Canadian National Radon Proficiency Program (C-NRPP) trained and certified. Our firm has trained professionals to assess buildings and give you the reliable answers you need. We would be happy to assist you on your next project or answer any questions you may have.
