Editing Radon (section)

=== Testing and mitigation ===
{{Main|Radon mitigation}}
[[File:Radon detector.jpg|alt=radon detector|thumb|A digital radon detector]]
[[Image:Radon test kit.jpg|thumb|A radon test kit]]
There are relatively simple tests for radon gas. In some countries these tests are methodically done in areas of known systematic hazards. Radon detection devices are commercially available. Digital radon detectors provide ongoing measurements giving both daily, weekly, short-term and long-term average readouts via a digital display. Short-term radon test devices used for initial screening purposes are inexpensive, in some cases free. There are important protocols for taking short-term radon tests and it is imperative that they be strictly followed. The kit includes a collector that the user hangs in the lowest habitable floor of the house for two to seven days. The user then sends the collector to a laboratory for analysis. Long term kits, taking collections for up to one year or more, are also available. An open-land test kit can test radon emissions from the land before construction begins.<ref name="epa" /> Radon concentrations can vary daily, and accurate radon exposure estimates require long-term average radon measurements in the spaces where an individual spends a significant amount of time.<ref>{{cite web |url=https://hps.org/publicinformation/ate/q10299.html |title=Answer to Question #10299 Submitted to "Ask the Experts" |last=Baes |first=Fred |website=Health Physics Society |access-date=2016-05-19}}</ref>

Radon levels fluctuate naturally, due to factors like transient weather conditions, so an initial test might not be an accurate assessment of a home's average radon level. Radon levels are at a maximum during the coolest part of the day when pressure differentials are greatest.<ref name="Thad. Godish 2001" /> Therefore, a high result (over 4&nbsp;pCi/L) justifies repeating the test before undertaking more expensive abatement projects. Measurements between 4 and 10&nbsp;pCi/L warrant a long-term radon test. Measurements over 10&nbsp;pCi/L warrant only another short-term test so that abatement measures are not unduly delayed. The EPA has advised purchasers of real estate to delay or decline a purchase if the seller has not successfully abated radon to 4&nbsp;pCi/L or less.<ref name="epa" />

Because the half-life of radon is only 3.8 days, removing or isolating the source will greatly reduce the hazard within a few weeks. Another method of reducing radon levels is to modify the building's ventilation. Generally, the indoor radon concentrations increase as ventilation rates decrease.<ref name="USPHS90" /> In a well-ventilated place, the radon concentration tends to align with outdoor values (typically 10&nbsp;Bq/m<sup>3</sup>, ranging from 1 to 100&nbsp;Bq/m<sup>3</sup>).<ref name="epa" />

The four principal ways of reducing the amount of radon accumulating in a house are:<ref name="epa" /><ref name="WHO291">{{cite web |author=World Health Organization |title=Radon and cancer, fact sheet 291 |url=https://www.who.int/mediacentre/factsheets/fs291/en/index.html |author-link=World Health Organization}}</ref>
* Sub-slab depressurization (soil suction) by increasing under-floor ventilation;
* Improving the ventilation of the house and avoiding the transport of radon from the basement into living rooms;
* Installing a radon sump system in the basement;
* Installing a positive pressurization or positive supply ventilation system.

According to the EPA, the method to reduce radon "...primarily used is a vent pipe system and fan, which pulls radon from beneath the house and vents it to the outside", which is also called sub-slab depressurization, active soil depressurization, or soil suction.<ref name="epa" /> Generally indoor radon can be mitigated by sub-slab depressurization and exhausting such radon-laden air to the outdoors, away from windows and other building openings. "[The] EPA generally recommends methods which prevent the entry of radon. Soil suction, for example, prevents radon from entering your home by drawing the radon from below the home and venting it through a pipe, or pipes, to the air above the home where it is quickly diluted" and the "EPA does not recommend the use of sealing alone to reduce radon because, by itself, sealing has not been shown to lower radon levels significantly or consistently".<ref name="epa.gov">{{cite web | url = http://www.epa.gov/radon/pubs/consguid.html#reductiontech| title = Consumer's Guide to Radon Reduction: How to fix your home| access-date = 2010-04-03| publisher = EPA}}</ref>

[[Positive pressure ventilation|Positive-pressure ventilation]] systems can be combined with a [[heat exchanger]] to recover energy in the process of exchanging air with the outside, and simply exhausting basement air to the outside is not necessarily a viable solution as this can actually draw radon gas into a dwelling. Homes built on a crawl space may benefit from a radon collector installed under a "radon barrier" (a sheet of plastic that covers the crawl space).<ref name="epa" /><ref>{{cite book |url=https://books.google.com/books?id=bspdQ8H2yUcC&pg=PT46 |page=46 |title=Building radon out a step-by-step guide on how to build radonresistant homes |publisher=DIANE Publishing |isbn=978-1-4289-0070-7}}</ref> For crawl spaces, the EPA states that "[a]n effective method to reduce radon levels in crawl space homes involves covering the earth floor with a high-density plastic sheet. A vent pipe and fan are used to draw the radon from under the sheet and vent it to the outdoors. This form of soil suction is called submembrane suction, and when properly applied is the most effective way to reduce radon levels in crawl space homes."<ref name="epa.gov" />