1、CAN/CGSB-149.12-2017National Standard of CanadaCanadian General Standards BoardRadon mitigation options for existing low-rise residential buildingsThe CANADIAN GENERAL STANDARDS BOARD (CGSB), under whose auspices this standard has been developed, is a government agency within Public Services and Pro
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21、 email ncr.cgsb-ongctpsgc-pwgsc.gc.caon the Web www.tpsgc-pwgsc.gc.ca/ongc-cgsb/index-eng.htmlHow to order Publications:Published November 2017 by the Canadian General Standards Board Gatineau, Canada K1A 1G6 HER MAJESTY THE QUEEN IN RIGHT OF CANADA, as represented by the Minister of Public Services
22、 and Procurement, the Minister responsible for the Canadian General Standards Board (2017).No part of this publication may be reproduced in any form without the prior permission of the publisher.Radon mitigation options for existing low-rise residential buildingsCETTE NORME NATIONALE DU CANADA EST D
23、ISPONIBLE EN VERSIONS FRANAISE ET ANGLAISE.ICS 91.120.99NATIONAL STANDARD OF CANADA CAN/CGSB-149.12-2017CAN/CGSB-149.12-2017 CGSB 2017 All rights reservedCANADIAN GENERAL STANDARDS BOARDCommittee on Radon Mitigation(Voting membership at date of approval)Chair (Voting)Whyte, J. Health Canada (General
24、 interest)General interest categoryBilal, M. Heating, Refrigerating and Air Conditioning Institute of CanadaBrossard, M. Health CanadaCryer, S. Pinchin Environmental Ltd.Krstic, G. Fraser Health AuthorityLafontaine, M. Physics Solutions Inc.Von Schoenberg, P. Public Services and Procurement CanadaWo
25、od, B. CARSTProducer categoryDalgleish, L. National Air Barrier AssociationForest, D. Venmar Ventilation Inc.Gelinas, P. Duchesne 2. the length and intensity of the cumulative exposure of an individual (to indoor radon) in the buildings where they spend most of their time.NOTE There are other lung c
26、ancer risk factors such as socio-economic, behavioral, occupational, biological and environmental. The combined effects of radon exposure and smoking tobacco can significantly increase the risk of lung cancer. Although the exposure to radon gas indoors and in occupational settings has been associate
27、d with an increased risk of developing lung cancer, there is not sufficient evidence in the published literature for the association with other diseases1. Due to a difference in air pressure between the inside of a building and the soil surrounding the foundation, soil gases, including radon may ent
28、er through openings in the foundation such as construction joints, gaps around service pipes and support posts, floor drains and sumps, cracks in foundation walls and in floor slabs, and openings in concrete block walls. Mitigation of existing homes with high levels of radioactive radon gas is a com
29、plex task, associated with many variables. It is recommended that radon mitigation be performed by a knowledgeable, specially trained radon mitigator such as a Canadian National Radon Proficiency Program (C-NRPP) certified radon mitigator.Radon is soluble in water and affects well water sources rath
30、er than surface waters which are more commonly used for municipal water supplies. When large volumes of water are used for domestic purposes, the radon dissolved in the water outgasses into the air. The health risk associated with radon dissolved in water is not from drinking the water, but from bre
31、athing the air into which the radon gas has been released. Potential entry routes for radon are illustrated in Figure 1.1 You can consult the World Health Organization (WHO) Radon handbook, September 2009 viewed 2017-07-13. Available from CAN/CGSB-149.12-2017iii CGSB 2017 All rights reservedNOTE 1 T
32、he only way to know if a home has a high radon concentration is to measure the radon concentration.NOTE 2 Figure has been taken from Health Canada, Radon Reduction Guide for Canadians, May 2014.Figure 1 Potential entry points of radon in foundation walls and poured concrete floorsIn 2007 the Governm
33、ent of Canada in conjunction with the Federal Provincial Territorial Radiation Protection Committee updated its guideline for exposure to radon in indoor air after a broad public consultation process which was based on new scientific information on health risk from indoor radon exposure.The current
34、Government of Canada Guideline for radon in indoor air is: Remedial measures should be undertaken in a dwelling whenever the average annual radon concentration exceeds 200 becquerels per cubic metre (Bq/m) in the normal occupancy area. The higher the radon concentration, the sooner remedial measures
35、 should be undertaken. When remedial action is taken, the radon level should be reduced to a value as low as practicable. The construction of new dwellings should employ techniques that will minimize radon entry and will facilitate post-construction radon removal should this subsequently prove neces
36、sary.For more information about radon and the Guideline, visit the Health Canada website https:/www.canada.ca/en/health-canada/services/environmental-workplace-health/radiation/radon.html#wb-info or call 1-800-O-Canada.4Potential entry routes for radon in homes with poured concrete foundations inclu
37、de cracks, areas with exposed soil or rocks, openings for utility fixtures or hollow objects such as support posts (see figure 1).Figure 1 nullypical radon entry routes in poured concrete foundation walls and nullors.in crawl spacesCracks or flaws infoundation wallsHollow objects such as supportpost
38、sAround utility penetrationsand support postFloor/wall jointsCracks or flaws in floor slabExposed soil or rock Floor drains the radon concentration in the soil gas; the building foundation design and construction; the pressure differences between the building and the soil.In addition to short-term v
39、ariations in indoor radon concentrations around the monthly average radon value, the monthly average itself varies from season to season, with the highest values usually occurring during winter months. Because of these variations, a measurement duration of at least three months during the heating se
40、ason will generally provide a conservative estimate of the annual average. If the result of the long-term measurement is greater than 200 Bq/m (5.4 pCi/L), Health Canada recommends that remedial action be undertaken. A short-term measurement of two to seven days is only acceptable as a rapid indicat
41、ion of radon concentration, for example, as an initial check on the success of a mitigation system installation. As it may not represent the actual long term average radon concentration, short-term testing should always be followed up with a long term test. The results of a short-term radon test sho
42、uld never be used to assess the need for radon mitigation in a house. While the health risk from radon exposure below the Canadian guideline decreases as the concentration is reduced, no level can be considered risk free. It is the choice of each homeowner to decide what level of radon exposure they
43、 are willing to accept. The mitigation method chosen is influenced by the initial radon concentration test results, the degree of radon reduction desired by the homeowner, the building type, and the costs associated with the method. How the basement or foundation area is used by a homeowner can affe
44、ct their expectations of the installation appearance and the cost. Mitigation of high levels of radon gas in a home may be accomplished using two basic methods. Either high levels of radon are kept from entering the building, or the radon which has already entered the home is diluted with outdoor ai
45、r. An established method of keeping radon from entering a building is active soil depressurization (ASD). ASD systems utilize a fan to create a negative pressure on the soil side relative to the interior of the building and thus exhaust the radon-laden soil gas to the outdoors where it is rapidly di
46、luted. Typical radon reductions associated with different mitigation techniques are presented in Annex A.The effectiveness of ASD in combination with sealing soil gas entry routes for radon control has been extensively proven, and the system typically does not significantly increase building energy
47、usage when it is well-designed and operated, therefore ASD should always be the first choice for reducing radon levels. ASD systems require little maintenance, function well for many years with an average fan life expectancy up to ten years, and typically reduce radon levels from 50 to 99%. Occasion
48、al replacement of the fan ensures the functionality of the system far into the future. The family of ASD systems consist of several different methods depending on the building construction.CAN/CGSB-149.12-2017v CGSB 2017 All rights reservedBuildings that have a fully poured concrete floor slab use s
49、ub-slab depressurization (SSD) and buildings that have exposed soil or other native materials use sub-membrane depressurization (SMD). Sump depressurization (SD), drain tile depressurization as well as block-wall depressurization are variants on soil depressurization where a depressurization fan is connected to a sump pit, drain tile network, or cavities of a block wall structure respectively to reduce radon levels. In SSD systems, the mitigation contractor cores through the existing concrete floor and connects to the gas permeable layer.
