Tag Archives: MD Home Inspector

Radon Measurement

The only thing Continuous Radon Monitors (CRM) do continuously is power their timers. “Why is that?”, you say. CRM timers tell the machines when to sample for Radon. Yes, that’s right, I said, “sample.”

Some popular machines only sample once every hour, others once every half-hour. Either way the most readings your getting over a 48 hour period is 96! The average of these samples is your result.

Everyone knows that the more samples you have the better their average represents the actual quantity.

The only way to get a truly continuous result is if you have a chemical reagent that changes over time. Film and photo papers are good examples of this. Exposure to light changes them over time.

Two Radon Measurement technologies exist that do just this. Each gradually changes over time when exposed to Radon continuously. The sample is the entire 48 hour time commonly allowed of Radon measurement for Real Estate transactions.

The most consistently accurate of these two are charged electrets. An electrical charge is placed on two electrets and measured before exposure to Radon. After the exposure time is complete (48 hrs.) they are measured again. Because the charge decays in the presence of Radon, the difference in readings will accurately measure the quantity of Radon in the home.

Radon equipment should be calibrated annually. Measurement should be done in the lowest livable level of the home. If the buyer intends to finish the basement it should be done there.

Your report should tell you where in the home the measurement was taken, the final result, and the equipment calibration date. The equipment calibration date should never be more than one year from the test date. This assures you that equipment maintenance is up to date.