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Guide for Radon Measurements in Public Buildings
8. Interpretation of Measurement Results
8.1 Long-Term Measurements in Public Buildings
If the long-term measurement results are below 200 Bq/m3, the average annual concentration in the home or building is probably below 200 Bq/m3 and further measurements are not necessary and remedial action is not recommended.
If the long-term measurement results are greater than 200 Bq/m3, then the average annual concentration in the home or building is probably above 200 Bq/m3 and remedial action is recommended.
8.2 Long-Term Measurements in Schools
The average radon concentration during school hours can be calculated from the radon data obtained from the long-term measurement and the short-term measurement using the continuous radon monitor. An average radon concentration during school hours (for example each day from 8 a.m. to 3 p.m.) during the overall short-term (48-hour or 7-day) test period can be obtained from the data collected by the continuous radon monitoring instrument. A ratio of this average radon concentration during school hours to the average radon concentration obtained over the full 48-hour or 7-day (whichever is applicable) short-term test period, gives the factor by which to multiply the long-term measurement result in order to obtain the long term average radon concentration during schools hours.
If the long term average radon concentration during school hours is below 200 Bq/m3, remedial action is not recommended.
If the long term average radon concentration during school hours is above 200 Bq/m3, remedial action is recommended.
8.3 Short-Term Measurements
The result of any initial short-term measurement (regardless of the result) should be confirmed with a "follow-up" long-term measurement. The follow-up measurement should be made at the same location as the initial measurement.
If the result of the long-term follow-up measurement is greater than 200 Bq/m3, then remedial action is recommended.
If the result of the long-term follow-up measurement is less than 200 Bq/m3, then remedial action is not recommended.
