Guide for Radon Measurements in Residential Dwellings (Homes)

5. Units of Radon Measurement

Canada, like most other countries, has adopted the International System of Units (SI units) and thus the radon guideline is given in units of Becquerel per cubic metre (Bq/m³). Therefore, in order to be able to compare a radon test result to the radon guideline, radon measurements must be made in units of Bq/m³ or the appropriate conversion must be applied to non-SI units (see table below).

However, the following information is provided: Depending on the measurement device used to complete a test, the measurement results may be in one of 3 units.

Units of Radon Measurement

Type of Device	Units Used	Comments
Devices that measure concentrations of radon gas	Becquerels per cubic metre (Bq/m3) (Canada)	1 Becquerel is equal to 1 disintegration per second
	picoCuries per Litre (pCi/L) (United States)	5.4 pCi/L is equal to 200 Bq/m3
Devices that measure the radiation emitted from radon progeny	Working Levels (WL) or milliWorking Levels (mWL)	Conversion from WL to Bq/m3 requires accurate knowledge of contingent factors.

Note: Care must be exercised in converting from units of radon progeny to radon gas as the ratio between the units depends on a number of factors.