The most asked about subject:
Radon (And Radon Decay Products [RDP])

Home owners, potential buyers & building owner/operators want to know:

BTW, every fact presented here is backup with active links by the EPA, official radon subject matter experts & groups, USGS and established health care resources. 121 PRO frowns on fuzzy science. 

  1. How can I have my building tested for radon? How accurate are the results?
  2. What about radon in my water system?
  3. When to test and how often?
  4. Does the EPA regulate radon testing professionals: NO! EPA stopped that on October 1998.
    1. The EPA recognizes a select few professional radon organizations and provides radon advisories only.
      1. National Radon Proficiency Program (NRPP)
      2. National Radon Safety Board (NRSB)
      3. Is you home inspector claiming to be certified? 
  5. What do the test results mean to me?
  6. Does the EPA still approve radon devices? No, that stopped on October 1998.
  7. What is the best credible consumer information for radon? Right here.
  8. What is the fix? Right here.
  9. How much area can one radon test cover? (Have you been miss informed?)
  10. Why does Flagstaff area have a higher percentage of radon?

As a Do It Yourself (DIY) home owner it is easy and economical to test for radon for indoor air & water. Keep in mind that radon levels in water will most likely be very different between public supply vs well-water due to the processing at the water treatment plant. Additional information regarding radon and water here. We recommend doing consumer grade 'long-term' testing: There are a few options to consider with long-term testing (90+ days). 1) A digital continuous monitor (see banner below), 2) A passive 91+ day long term test, 3) A passive 180+ day test which spans winter & summer. Long-term radon testing, when compared to a 48 hour test, provides a more accurate picture of radon levels in a building. Radon emanating from the earth may change over time at any location (increase or decrease), therefore the Surgeon General states the following: "Radon gas in the indoor air of America's homes poses a serious health risk. More than 20,000 Americans die of radon-related lung cancer every year. Millions of homes have an elevated radon level. If you also smoke, your risk of lung cancer is much higher. Test your home for radon every two years, and retest any time you move, make structural changes to your home, or occupy a previously unused level of a house." Additionally, the defining research on radon health effects here. Here is the defining research and recommendations from the World Health Organization.

Corentium Home by Airthings large image bannerOk, so you want a short-term 48+ hour radon test, which is very common, but you want to do it right...naturally.  Here are the top reasons that invalidate the results (not an exhaustive list):

  1. FAIL: The person setting up the testing units is unaware of the proper methods & the necessary communication regarding the testing/sampling & lab procedures.
  2. FAIL: If radon testing canisters are used and the associated paperwork is incorrectly completed (such as the wrong date of sampling: a common mistake). This will invalidate the test because radon has a short half-life: labs use the dates provided on the paperwork during testing.
  3. FAIL: Certified electronic radon measuring devices not calibrated: Lack of annual calibration means unreliable results (Ask for proof of calibration). Results from a radon measuring device that has not been properly calibrated will not withstand litigation.
    • Certified electronic radon measuring devices require calibration every 1 or 2 years.
  4. FAIL: HVAC systems operating during the short-term testing period which may introduce outside air. Remember to turn it off if outside air is pulled into the house.
    • NOTE: Keep in mind that the house needs to be 'closed' 12 hours prior to a short-term radon test. Additionally the house needs to remain closed for the duration of the test. An important consideration: It is OK to run the HVAC system during testing only under these conditions 1) No introduction of outside air through HVAC or other method 2) Heat created by the HVAC system must not be excessive, doing so pulls outside air into the house through tiny house cracks and leaks as the heat rises into the attic (stack effect). Also, this is obvious: Do not operate any wood burning stoves. If radon results are 4 pCi/L without HVAC then a 2nd test is conducted with HVAC in operation.
  5. FAIL: Open windows and doors. A building or home should be closed with the lowest potential for air movement.
  6. FAIL: Testing during high winds, high humidity or a strong weather pressure system.
  7. CAUTION: Seller/agent masking or tempering: Yes, unfortunately, this does exist. This unethical behavior is common enough that the EPA dedicates an entire section of the Home Buyer’s and Seller’s Guide to Radon to it (page 13). A select few certified radon measuring devices will detect these activities.
    • Masking and tampering with the radon measuring device includes:
      • Device placed in a container, wrapped in a bag or foil
      • Device moved from the measuring location (outside or the refrigerator is common)
      • Intentionally blocking the device's measurement intake ports with tape or similar.
    • Placing a portable humidifying fan next to the device.
    • Intentionally turning on excessive furnace heat or using an air handler to circulate outside air indoors.
    • Intentionally opening doors and windows.
  8. CAUTION: Types of radon measuring devices and how they might be a FAIL.
    • FAIL: Devices that are not certified (do your research!)
      • The EPA stopped the "EPA Approved" device program in October of 1998. The only certifying program is managed by AARST-NRPP.
    • IMPORTANT: Radon detection devices which are consumer use only (These are not intended to establish certified results and will not withstand litigation)
      • FAIL: Professionals who use these devices are almost always not officially trained in Radon Measurement.
    • Professional certified devices will give bad results for the following reasons:
      • FAIL: The so-called radon measuring professional was not properly trained to follow the necessary radon measurement steps: The steps may have been neglected or the so-called professional may not be aware of the procedures.
      • FAIL: This is a repeat of #3 - Certified electronic radon measuring devices not calibrated: Ask for proof of calibration, which is every 1 or 2 years.

OK, the big question:
What are the EPA recommended thresholds (Green Light/Red Light)

Radon test results in the United States may be reported in two different measures: Picocuries (pCi/l) & Working Levels (WL).

If your test result is in pCi/L, EPA recommends you should take action to fix your home if the radon level is 4 pCi/L or higher. If the results are between 4 and 2 the EPA encourages you to consider taking action. The goal is 2pCi/L or less.

  • The average indoor radon level is 1.3 pCi/L.
  • The average outdoor radon level is 0.4 pCi/L.

If the test result is in WL, EPA recommends you fix your home if the working level is 0.02 WL or higher (4 pCi/L = 0.016 WL).

Picocuries (pCi/l) and Working Levels (WL) measure different types of radon:

  • Picocuries (pCi/l) measure radon gas (Rn-222) NOTE: Radon gas decays into radon decay products listed next.
  • Working Levels (WL) measure radon decay products (byproducts of radon gas decay): Polonium- 214 and 218, Bismuth 214 & Lead 214.
  • Another measurement type is the Equilibrium Ratio which is a ratio of the  expresses as  (WL x 100) ÷ (pCi/l)

How are RDPs different from actual radon? The characteristics of RDPs include:

  • RDPs are the byproduct of radon gas.
  • They are the source of cell damage in the lungs.
  • They are short-lived products (less than 30 minutes), but the most significant.
  • They have static electrical charges. They are chemically reactive.
  • They are solid particles, rather than gases, that act like invisible aerosols in the air.
  • They are classified as heavy metals.
  • So, why is almost all testing of radon gas: 1) It is less expensive and more reliable 2) The predictability of radon gas concentration and the rate it develops the RDPs is very accurate.

A quick look at radon health statistics:

Non-smoker - Per 1,000 people radon caused lung cancer:

  • At 4-pCi/L is 7 people will possibly develop lung cancer
  • At 2-pCi/L is 4 people will possibly develop lung cancer

Smoker - Per 1,000 people radon caused lung cancer:

  • At 4-pCi/L is 62 people will possibly develop lung cancer
  • At 2-pCi/L is 32 people will possibly develop lung cancer

At 121 PRO we are serious about radon, your health and the value (and accuracy) of data.

Keep in mind that the EPA (BEIR VI), ASTM, NRSB, & AARST-NRPP all state what is commonly known: The radon test should be performed in the 'lowest' living or daily occupied space of a building. If a building or house is 6000 square feet but the lowest living space is at or below 2000 square feet then only 1 radon test is necessary (So, do not pay for more than one test). If there are multiple buildings then a single radon test should be performed for each building (Yes, radon measurements can be distinct, dissimilar and unrelated from one building to another adjacent building).  Anytime the 1st floor above the soil is greater than 2000 square feet then the EPA recommends 1 radon test per 2000 feet. This is based on the EPA guidelines for measuring radon in schools. Of course, practical judgement is applied case by case when the lowest level square footage is between 2000 and 3000 square feet. The average home size in the south west is less than 2,400 square feet, so a single radon test will most likely work.

Why does Flagstaff area have a higher percentage of radon?

Radon transports easily through limestone rich areas where water has naturally eroded the rock particularly above aquifers and limestone caves . Interestingly enough, the Flagstaff area sits on top of a large layer of limestone called Kiabab Limestone which is part of the Colorado Plateau system and the 'C-Aquifer'.

Radon Device Calibration

accuracy vs precision


AARST & NRPP certifies & approves devices

radon tester

Radon Result of 4+

  • EPA says ‘Take Action’

Radon Result between 2 & 4

  • EPA says ‘Consider Taking Action’

IAC2 Radon Certified IAC2 Mold Certified