Continuous Radon Monitoring vs. “the two little vials” – Facts and Myths about Radon Gas Testing – Part II

Home Inspector with BONSAI Inspection Company

This is part two of my little 'mini-series' on the differences between the two most common real estate transaction/radon gas testing methods. In part I, I addressed the primary similarity that being accuracy. In this blog installment, I'll be sticking to differences. I'd like to cover a few pros and cons of each.

Cost -  Advantage: Vial test

Most good quality kits cost the average inspector $20-$30, so you're typically looking at a cost in the $50-$75 range. For the machine test, factoring in the system's cost (upwards of $600) and the 'tie up' time, and you've looking at a typical $100-$150 per test.

Speed - Advantage: Machine test

We all know time is king in this business. Assuming a minimum 48-hour test interval, for the vial test results the typical turnaround is 5-7 business days from the start of placement. The machine? Wait 48 hours, show up, push button, done.

Simplicity - Advantage: Vial test

Don't discount simplicity as a potentially significant advantage. The vials require no calibration, don't care if the power is off or turned off, have no cords, don't need a back-up battery, and have no moving parts or 'down time'. If it 'can' go wrong with an electronic device, at some (most likely inopportune) time, it will.

"Tamper-proof" - ness - Advantage: Machine test

While no test is 100% tamper-proof, the machine test can be. I have added temperature and relative humidity monitoring to my system to make testing virtually fool-proof. The vials require a small leap of faith that tampering has not occurred, however the test is not as easily fooled as it may seem.


So, like most other things in life, we see that there are plusses and minuses to the majority of A vs. B choices we are faced with every day. In the end, it all boils down to each individual clients specific needs and finances. As long as accuracy remains the same, no test method presents a clear advantage over the other.

I hope this little 'mini-series' on radon testing has shed a little light on this rapidly developing aspect of the real estate industry.

Comments (2)

Bruce Breedlove
Avalon Inspection Services - Colorado Springs, CO

Another thing to consider is a CRM can be used for radon testing lasting several days, weeks, even months (provided the memory has enough data points for the sampling interval and measurement duration). This makes a CRM great for longer-term testing or to gather additional data (e.g., how radon levels are affected by changes in weather or changes in how the house is used).

Activated charcoal radon devices (charcoal canisters, charcoal envelopes, liquid scintillation vials, etc.) are limited to a maximum measurement duration of 5 to 7 days because radon attaches to the charcoal and rapidly decays away. With a half-life of about 3 1/2 days 75% of the radon that attached to the charcoal during the first hour of the measurement will have decayed away after a week. This is accounted for by the processing lab but, as you can see, it does affect the accuracy of the measurement.

Feb 02, 2010 12:49 PM
Mike Ciavattieri
BONSAI Inspection Company - Weymouth, MA
Home Inspection Massachusetts

GREAT POINT, Bruce..  thanks! I was hemming and hawing a bit trying to maybe come up with another point - but in the end I came up blank.

Please - any other points are more than welcome here


Feb 02, 2010 01:01 PM