Active soil depressurization (ASD) (dépressurisation active du sol (DAS))

Group of radon mitigation systems involving fan-powered soil depressurization, including but not limited to the

most common variant called sub-slab depressurization, and other related techniques such as sub‑membrane

depressurization (ex. crawl space depressurization), block-wall depressurization, and drain tile depressurization.

This fan-powered soil depressurization is employed to draw radon-bearing soil gas away from the foundation and

safely exhaust it outdoors before it can enter a building.

NOTE ASD is the most effective way to reduce high radon levels in a building, with reductions of >90% or more being possible.

ASD fan (ventilateur de DAS)

type of fan that is designed and approved by the manufacturer for continuous duty and for use in an ASD radon

reduction system.

As low as reasonably achievable (ALARA) (le plus faible qu’il soit raisonnablement possible d’atteindre

(ALARA))

internationally recognized guiding practice employed in radiation protection.

NOTE ALARA indicates that radiation doses be reduced to as low a level as practical, with economic and social factors being

considered.

Becquerels per cubic metre (Bq/m3) (becquerel par mètre cube (Bq/m3))

SI unit of measure for the concentration of radioactivity in a volume of air.

NOTE One becquerel is one radioactive disintegration per second. The American unit that measures radon is picoCuries per

litre (pCi/L). 37 Bq/m3= 1 pCi/L



Canadian national radon proficiency program (C-NRPP)

The national radon certification program used by laboratories, measurement and mitigation professionals in Canada.

NOTE C-NRPP may provide designations to individuals or companies that have met qualification requirements or are

authorized by a certification program to provide radon laboratory, measurement or mitigation services.

Canadian radon guideline (ligne directrice canadienne sur le radon)

the indoor radon concentration at which mitigation is recommended, which was set at 200 Bq/m3, as established by

Health Canada in 2007 (Canada Gazette Part I, June 9th 2007).



Communication testing (test de communication)

the typical process whereby a radon mitigator makes diagnostic pressure measurements of the under slab area in

order to properly size an ASD mitigation system.

NOTE Properly sizing an ASD mitigation system includes determining the type of fan(s) to be utilized, fan location, and number

of required suction points.

Crawl space (vide sanitaire)

shallow space between the lowest floor of a house and the ground beneath.

NOTE The crawl space can have a height ranging from a few inches to several feet (hence the origin of the term “crawl”). The

crawl space may or may not be ventilated to the outdoors.

Depressurization (dépressurisation)

a negative pressure induced in one area relative to another.

NOTE In a building during cold weather, the lower levels experience depressurization due to the stack effect (buoyant forces

acting on the warm air). The air pressure within the soil outdoors is also often higher than that in the basement which also acts

to draw soil gas into the building.

Diagnostic tests (tests diagnostiques)

procedures that typically include communication tests used to identify or characterize conditions under, beside

and within buildings that could contribute to radon entry or elevated radon levels or that could provide information

regarding the performance of a radon mitigation system.

Habitable space (espace habitable)

any enclosed space that residents use or could reasonably adapt for use as living space within the building.

Low rise residential building (maison et petit bâtiment)

building three storeys or less in height, having a building area not exceeding 600 m2.

Radon mitigation (atténuation du radon)

act of repairing or altering a building or building design for the purpose in whole or in part of reducing the concentration

of radon in the indoor atmosphere.

Neutral pressure plane (plan de pression neutre)

that plane within the building envelope at which the pressure indoors equals the pressure outdoors.

NOTE During cold weather, when the thermal stack effect occurs, indoor pressure below the neutral pressure plane is

lower than the pressure outdoors, so outdoor air and soil gas may infiltrate the building. Above the neutral pressure plane,

indoor pressure is higher than the pressure outdoors so that building air may exfiltrate the building.

Outdoor ambient radon level (niveau de radon ambiant dans l'air extérieur)

the concentration of radon naturally occurring in outdoor air.

Post-mitigation radon level (concentration de radon post-atténuation)

the radon concentration measured within the habitable space of the building as a result of a long-term (3 months/

90+ days) radon test conducted after radon mitigation work has been performed.

NOTE The radon level should be reduced to below the Canadian guideline value of 200 Bq/m3 and in fact to ALARA (as low

as reasonably achievable). For most buildings it will be possible to reduce the radon level to below 100 Bq/m3. It is recognized

that it may not be possible to reduce radon levels below 100 Bq/m3 in all buildings by following the best practices outlined in this

standard. The 3-month test is ideally conducted during the heating season to give a conservative estimate of the radon reduction

achieved.

Radon (radon)

the only naturally occurring radioactive element which is a gas.

NOTE Technically, the term “radon” can refer to any of a number of radioactive isotopes having atomic number 86. In this

document, the term is used to refer specifically to the isotope radon-222, the primary longest-lived isotope present inside

buildings. Radon-222 is directly created by the decay of radium-226, and has a half-life of 3.82 d. Chemical symbol: Rn-222.

Slab (dalle)

layer of concrete which commonly serves as the floor of any part of a building whenever the floor is supported on a

foundation or is in direct contact with the underlying soil.

Abbreviations and acronyms

The following abbreviations and acronyms are used in this standard:

ABS: Acrylonitrile-butadiene-styrene

ALARA: As low as reasonably achievable

ASD: Active soil depressurization

ASTM: American Society of Testing and Materials

ATD: Alpha track detector

CGSB: Canadian General Standards Board

C-NRPP: Canadian — National Radon Proficiency Program

CRM: Continuous radon monitor

EIC: Electret ion chamber

SDS: Safety data sheet

DWV: Drain, waste, and vent

NBC: National Building Code (of Canada)

PFE: Pressure field extension

PVC: Poly Vinyl Chloride

SCH: Schedule (as in pipe thickness)

SDR: Standard dimension ratio

SMD: Sub-membrane depressurization

SSD: Sub-slab depressurization

WHO: World Health Organization

ICF: Insulated Concrete Form