Continuous monitors have a higher degree of sensitivity in sampling radon than charcoal kits do. However, not all monitors are created "equal". Just as you have varying degree of quality in "car" (Kia, Honda, Cadillac, Mercedes etc), the same is true for continuous radon monitors frequently used today.
The main difference is in the amount of "radon samples" takes every hour. Just as student who takes a test in school, if you base their annual performance on the results of one test, you may be making some very risky "assumptions". The more tests a student takes, the more his/her "high scores" and "low scores" are averaged together so that one specific test is not given too much "weight"
A standard "acceptable" radon test (according to EPA testing protocols) is conducted for a minimum of 48 hours. A continuous monitor takes a radon sample "hourly" and the results are a summary of the "average" for the test period conducted. However, while the "hourly average" is generated by a continuous monitor, the key is HOW each monitor arrives at that hourly average that it generates. The answer is that every continuous monitor takes a series of radon test samples every hour and these numbers are "averaged together" to produce the hourly average produced on the final report. The key to the "sensitivity" of each monitor is based on the number of radon samples each monitor takes every hour. The more samples taken, the closer the averages produced are to the true monthly and yearly average in a home.
This understanding is critical in assessing the credibility of each monitor.
We use continuous monitors that take (19) hourly samples. The monitors which most home inspectors use only take 4 samples. This means that our monitors take over 4 times as many samples as their lower priced counterpart. Furthermore, in addition to hourly samples for radon, our monitors also take hourly readings for humidty, temperature and barometric pressure. They are powered by a lithium battery and are NOT AFFECTED by "electrial spikes and surges" the way AC powered units are. All this information helps the certified professional best assess whether there were valid test conditions maintained during the duration of the test. If you are a homeowner, who has hired someone to conduct a radon test for you, you want to kNOW that the information you are provided is accurate!