121 PRO has the largest inventory of radon monitoring devices north of Tucson & by 2021 we will have the largest inventory in AZ. We are certified and approved to test for government buildings, hospitals, all universities & school district buildings, large multi-family buildings & hotels. Of course, we test residential building too.

Each radon test for residential buildings includes on-site testing with 2 radon monitoring devices for unquestionable results. Certified professional testing is completed by an EPA recognized NRPP radon professional. Each radon report (usually 8 pages) includes 2 to 3 pages of professional notes interpreting the entire length of the test.

There are only 3 certified professionals north of Phoenix: Bill Branch, John McCartney & Drew Ramsey (Verify here) or visit our FaceBook page. Also, here is our presentation at Northern Arizona Association of Realtors. Here is a quick video on radon certification.

Why choose a properly certified radon professional which is recognized by the EPA? Because we believe that your health is sacred.

Additionally: We review radon reports at no cost to you.


The most asked about subject:

Home owners, buyers & commercial building owners want to know:

  1. How accurate are the results? Each home is tested with two radon monitoring devices for unquestionable results. 
  2. 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? 
        1. Find out here.
  3. Does the EPA still approve radon devices? No, that stopped on October 1998.
  4. What is an 'EPA certified 48-hour measurements'. WARNING: This is a misleading sales tactic, no EPA radon certifications of any type exist. All radon measurement protocols are published at AARST.
  5. What do the test results mean to me? 121 PRO provides very detailed analysis of the results: usually 2-3 pages of professional notes added to the 6 page report.
  6. What is the best credible consumer information for radon? Right here.
  7. What is the fix? Right here.
  8. Why does Flagstaff area have a higher percentage of radon? Read below for a complete and comprehensive answer.

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. 

As a Do It Yourself (DIY) homeowner it is easy and economical to test for radon indoors &  in 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. 121 PRO recommend doing consumer grade 'long-term' testing: There are a few options to consider with long-term testing (91+ 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 banner

Ok, so you want a short-term 48+ hour radon test, which is very common, but you want to do it right...naturally. Here is the list to prepare for the radon test:

  1. Make sure the your house is closed for 12 hours prior. Easier to do in the winter, but in the summer sometimes children will leave a window or door open for a few hours. So, please keep the windows closed. As far as entering or leaving the home, that is ok...just close the door right after you open it.
  2. Do not operate 'Whole House" fans...operating this while the doors & windows are closed may pull more radon through the floor.
  3. Do not operate HVAC systems which introduce outside air.
  4. Do not operate a fireplace unless it is the primary source of heat.
  5. Do not operate gas appliances other than the water heater, furnace and gas stoves.

Is it possible to cheat the test?

It is easy to pull the wool over the eyes of so-called radon testers who are not certified including sudo-certified radon testers. In most cases they will only look at the final reported radon level for the 48 hours and say 'pass' or 'fail'. BUT the data during the 48 hours will provide clues which may indicate test tampering OR clues to healthier living. Here is how we know: The radon devices also record indoor barometric pressure, humidity and temperature. When windows & doors are opened without the HVAC system running the barometric pressure and humidity levels slowly change to match the outside environment. If the windows and doors are open with the HVAC system running we see a rapid change in both indoor temperature and barometric pressure. If there are fans at crawlspace openings we see rapid changes in barometric pressure and slightly less change in humidity which matches the same timeline of change. This is not a complete list but 121 PRO has a video coming out soon to explain all this better.

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

The 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. (Flagstaff average is roughly 2.7)
  • The average outdoor radon level is 0.4 pCi/L.

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

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