There are three basic methods for measuring radon and RDPs:
A) Time Integrated – Passive Devices
Most radon measurements will be obtained over a short period of time, generally a few days to a week but sometimes up to a year. Devices that sample over such time periods and average the results are called integrating detectors or instruments. Sample collection may be either passive (no electrical power needed) or active (power needed). Passive integrating devices – such as activated charcoal devices (ACs) and alpha track detectors (ATDs) – are particularly useful, because of their simplicity, low cost, and ability to average out short-term variations in concentration. Active integrating devices, such as continuous radon and working level monitors, are able to integrate and track the variation in radon and RDPs.
B) Continuous – Continuous Monitors
Continuous Sampling is conducted over short periods of time to provide measurement of the variation in radon and RDPs. This type of sampling is conducted with continuous radon monitors (CRMs) and is typically used in research and real estate transactions.
C) Grab Sampling – WL Monitors
This technique involves collecting a representative air sample from the building over a short period of time, usually only a few minutes. It is essentially an instantaneous measurement: the radon or RDP level found is indicative only of the concentration at the time of sampling. Grab samples are helpful in providing quick feedback during the diagnostic and mitigation processes.