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10 Tips For Measuring Radon in Your Home

There are three options for measurement of radon level in your house (listed in order of increased cost):

  1. Purchasing radon gas test kit (cost about $11 for short-term, and about $26 for long-term), deploying it, and mailing it to the test lab (additional lab fee of $40).
  2.  Buying radon monitor; three models are currently available:  a) Safety Siren Pro Series 3 (cost about $130, b) Correntium QRI Radon Digital Monitor (cost about $150-$175) , c) Radon Eye RD200 (cost $175 – $200). This method allows for continuous radon monitoring.
  3.  Hire a licensed radon measurement Provider (cost $150-$250). This is the only option for measuring radon for  real- estate transactions in Montgomery County MD.

Although Radon Gas Test Kits may be the least expensive option, they have many potential pitfalls that can produce false results. Here are ten tips that can help prevent the pitfalls:

Tip #1. Purchase kits that have two liquid scintillation vials (e.g., the Pro-Lab Radon Gas Test Kit). Kit with two detectors will yield higher accuracy than kits with one detector.

Tip #2. Do not buy kits that are more than three years old. Short-term kits have a shelf-life of three years (fact not disclosed by most kit manufacturers).

Tip #3.Keep exterior doors and windows closed (normal entry/exit is OK ) 12 hours prior to, and for the duration of, the test (this is called “close-hose condition”).

Tip #4.Place BOTH radon-detecting VIALS in the lowest-livable  level of the house (usually finished or unfinished basement but not cellars) at the SAME spot 4” apart.

Tip #5. Vials location SHALL be at LEAST 20 inches from the floor: radon gas is slightly heavier than the air, thus placing detecting vials on the floor will yield higher measured radon levels.

Tip #6. Place radon-detecting vials at least 3 feet away from winndows/doors/fireplaces. Draft from these places can lower measured radon levels.

Tip #7. Do NOT place radon-detecting vials near/under air-registers (both, supply and return). Air flow from/to registers will lower measured radon level.

Tip #8. Do NOT place radon-detecting vials in the kitchen/laundry room/ bathroom/utility room/closet/stairways/crawl-space/cellar. These locations can have air turbulence (from exhaust fans/ close dryers) or higher radon accumulation (such as in a crawl-space) that will yield  erroneous measured radon level.

Tip #9. Do not run window A/C with fresh air intake (recirculate setting is OK). HVAC setting should be on NORMAL (no continuous fan operation). Whole house fan should be OFF. Do NOT use clothes dryer. Operation of these units can cause a lower measured radon level.

Tip #10 (MOST IMPORTANT). Start the test on THURSDAY,  finish on MONDAY , and mail test kit to the lab MONDAY MORNING. The half-life of radon is 3.8 days (50% of captured radon in the vials is lost), and IF vials arrive to the lab on Thu./Fri and processed only on Mon., too much of captured radon is lost to get accurate results. Typically IF four or more days passed between the date the test was terminated and the date the lab processed (not received) it, the results are QUESTIONABLE.

For more details on measuring radon, see EPA’s Guide to Radon.