Can Radon Levels Fluctuate Inside A NJ House?

Do Radon Levels Fluctuate Inside A Typical NJ Home? | Radon Inspector Brick NJ

January 15, 2023

As part of a home inspection done on a home in Red Bank, NJ, Regal Home Inspections, LLC performed a radon test. This occurred about 4 years ago. Following the protocols for the placement of the radon test, it was conducted over a 2, 3 or 4 day period. I don’t recall the exact interval but I know, 100%, that it was done following the testing requirements. Those requirements have a minimum exposure time of 48 hours and as many as 144 hours (e.g. the equivalent of 6 full days). The test came back below the NJ DEP’s, “Action level” of 4.0 pico Curries per liter of air (pCI/L) so there was no further action that needed to be taken. Case closed. A couple of years later I received a call from the young lady that hired us for the Red Bank inspection and radon test because they had decided to sell that home and when the new buyer did their radon test it came back ABOVE 4.0. She asked can that happen and I said, “Yes” it’s possible. That radon levels can fluctuate inside a NJ home.

In 2022, we did another home inspection including a radon test and this time, the test we did in association with the home inspection came back ABOVE 4.0pCi/L. The seller disagreed, hired someone else to do a test and the second test came back below 4.0.  The seller complained but didn’t understand that radon levels can change. She complained that I had done something that made the test come back high.  In my response I stated that, “It’s not like I carry a spray can of radon with me!”  Additionally, I called one of the labs we’re affiliated with to ask a lab specialist if it’s possible for someone to fake a high result. His response was basically if the radon canister was opened, placed upside down on the basement’s concrete floor over a crack in the floor it’s nearly impossible to fake a high reading.  Now please remember that A) Radon is one of the elements on the Periodic Table of the Elements. Just as is Oxygen, Helium, Iron, Gold, Uranium, etc. B) It’s a radioactive element so unless one wants to expose themselves to Alpha radiation, Beta radiation or Gamma radiation, it’s not a good idea to mess around with this stuff.  It’s not like I can sprinkle some radon pixie dust on the test device to fake a high reading. C) The test device has to be placed following recognized protocols which we ALWAYS do.

Dealing With Radon In The NJ Home

Those are two anecdotes that give a little background. For over 31 years my family and I have lived in an area identified by the NJ DEP as a Tier 1 or “High radon potential” area.  During the 10 years or so that I’ve been a home inspector and certified to conduct radon testing I’ve tested my home (In the basement) about 5 times. The results have always been between 2.4 and 2.7pCI/L. Late, last winter (2022) I purchased an active radon monitor. It hangs on the wall like a thermostat. It has an app to by smartphone and constantly measured for radon. Here’s an actual photo of the monitor. It’s manufactu-red by a company called AirThings

Radon Levels | Radon Inspector Brick NJ
AirThings Monitor in my basement.
radon levels app | radon inspector brick nj
Screenshot of the app on my phone on 1/15/2023.

and I urge everyone to have one in your home. Their website is…  Airthings | check it out for the leading radon and indoor air quality monitors. Radon is the leading cause of lung cancer for non-smokers and 2nd only to cigarettes in causing lung cancer. Estimates are that 21,000 people die each year from radon caused lung cancer.

Again, the AirThings monitor was installed in the late winter of 2022. Everything looked good and the monitor read, as I was expecting, in the 2.5pCi/L range. Then Spring arrived. What do many of us do when spring arrives and the outside temperature rises to the mid 60s or 70s? We open all the windows as we did.  About 2 days later the AirThings app on my phone issued an alarm of sorts. MUCH to my surprise, it notified me that the radon level in my basement rose above 4.0!!!  The radon training requires that the test be done while maintaining, “Closed House Conditions.”  That means no open windows, refrain from using the fireplace, etc. Why, because as I experienced 1st hand, opening the windows and airing out the house can cause negative pressure inside the house. Naturally the house wants to equalize the pressure which, in my case, led to drawing radon into the basement.

To rectify the situation, I opened a couple of windows in my basement. Just a crack, mind you, but enough to get some fresh air in. That seemed to do the trick. The average radon level dropped to below 2.0 and often close to 1.0pCi/L.

Then…I turned on a portable heater in my basement. There is some heat from the forced hot air heating system but I was working on a project and painting some cabinet doors that had been removed and placed on a couple of tables in the basement. With the intention of increasing the temperature of the basement to aid in the paint drying a little quicker, I turned on a portable, electric heater and closed the windows.  It did the job I wanted it to do and the basement was nice and warm. However, warm air rises. I believe what happened is that as the warm air rose from the basement it, again, created negative pressure inside the basement. The way the house equalized the pressure was to draw air into the basement from the perimeter drain, etc. That caused the radon to spike to 3.0pCi/L. My project is done. The heater is off and the window is open again and the radon levels are going down.

Key Takeaways | Dealing With Radon In The NJ Home

So, what are the key take aways from this story?

  • Radon levels change. Do not ASSUME that if it tests low once that it will always be low.
  • Test regularly if that’s possible.
  • And test at different times of the year. Since your home’s conditions may change seasonally, test seasonally until you get a good indication how the radon potential changes year-round.

If you have any questions or would like to discuss your specific situation, please call either Brian or Frank at Regal Home Inspections, LLC. We’re both licensed by the NJ DEP to test for radon.  Regal Home Inspections, LLC is licensed to test for radon in single family homes, townhouses, duplex homes, single unit condominiums. Frank is also licensed to perform radon testing in commercial buildings, large and small and schools including preschools and child care centers. Commercial buildings, large and small and schools including preschools and child care centers require a great deal of pre-testing analysis, coordination and fact finding and then strict adherence to the rules set forth by the American Association of Radon Scientists and Technologists (AARST).

Call – Brian @ 732 740 8365 or Frank @ 908 902 2590.

Radon. What does 4pCi/L mean and why is it important?


What does 4.0pCi/L represent?

By Frank J. Delle Donne, Licensed Home Inspector

January 16, 2014

About the author.  I am a NJ Licensed Home Inspector.  I am the owner and Senior Inspector at Regal Home Inspections, LLC.  I have been a volunteer Emergency Medical Technician for over 20 years and was  a past member of the Colts Neck, NJ Board of Health and was Chairman of that Board for 2008 and 2009.    During my studies to become a Home Inspector and earning my NJ Certification to be a Radon Measurement Technician I learned a great deal about Radon and felt compelled to share that information in a manner that is easy to understand and increases awareness.  Every home in New Jersey should be tested for Radon on a regular basis.  Regal Home Inspections, LLC is having a New Year 2014 SPECIAL on Radon testing.  These discounted prices are good through February 28, 2014.  Please call now to schedule your Radon test.

The federal Environmental Protection Agency (EPA) has been leading the effort to make citizens aware of radon and closer to home, the NJ Department of Environmental Protection (NJ-DEP) has been following suit.  Please read our earlier post for general information about radon.   This piece is intended to explain the measured results; When is it an issue and when is it not?


A few points that I’d like to repeat from the earlier article is that radon is everywhere and it is naturally occurring.  It is a radioactive gas which means that it transforms spontaneously and in that transformation it releases tiny bursts of energy.  It is these tiny bursts of energy that cause harm.

Radon, like other radioactive materials, are measured in pCi/L.  This stands for pico Curies per liter of air.  A “pico Curie” is one-trillionths of a Curie.  A Curie is equivalent to 37 Billion radioactive disintegrations per second.  Therefore one pico-Curie works out to 2.2 radioactive disintegrations per minute (dpm) in a liter of air.  A “Curie” is of course named after Marie Curie who lived in the late 1800s to the 1930s.

Action Level

The EPA (and NJ-DEP) refers to 4.0pCi/L as measured over a minimum of 48 hours as the Action Level for radon mitigation.  This applies uniformly to real estate transactions and for the self motivated homeowner who tests for radon, they too should mitigate at this, measured level.

As mentioned in the previous article, the radioactive disintegrations take on three different forms.  There is Alpha radiation, Beta radiation and Gamma radiation.  The result of a, “disintegration” is a new element (Polonium, Lead, Bismuth or Radon) but the process that the atoms change also releases energy in Alpha, Beta or Gamma form.

At 2.22 dpm per pico Curie at 4pCi/L (assuming each one of your lungs holds a liter of air) that’s 16.88 (8.44 per lung) radioactive disintegrations that are occurring inside your lungs!  While these releases of energy are extremely tiny, they have the potential to damage cells and DNA.  This can lead to the events that begin the formation of mutant or cancerous cells.

So is 3.5pCi/L that much better?  Not really but for the real estate transaction, a radon test measurement that reads 4.0pCi/L will result in a letter from the buyer’s attorney to the seller/seller’s attorney stating that the seller must mitigate the radon and provide new test results that show the level is, post mitigation, less than 4.0pCi/L.

At or above 4.0pCi/L and a letter is coming.  A reading of just below 4.0pCi/L may ask for a second test where the two tests might be averaged.  Rest assured that at or above 4.0pCi/L and the seller will be calling a radon mitigation company.


Radon mitigation comprises of a system, usually a vent, that will reduce the measured radon inside at the lowest, “livable” area.

A very common type of mitigation system is a sub soil depressurization system.  In this method, a pipe is placed below the concrete basement floor.  That pipe (usually a 4” PVC pipe) is routed to the outdoor and a fan is placed to draw the air (and radon) from below the basement floor and vent it to the outdoors before it enters the house.  With this system the basement floor has to be sealed which means that sump pits are sealed and French drains are sealed.   Also, any cracks or other basement floor penetrations must also be sealed for the sub soil depressurization system to be most effective.

The white pipe is the radon mitigation system pulling air and radon from below the basement floor, up and outside before the radon gas enters the house. The area of the vent system that bulges out is a fan. The fan runs constantly.

The cost for such a system can be as low as $1500 but based upon many factors could be higher.   After the system is installed and activated, it should be left operation AT ALL TIMES.  It should be operating for at least 12 hours to allow “Dynamic Equilibrium” to occur.  This is a fancy way for saying that the positive effects of the new mitigation system should be set in place after 12 hours.  After this period of time a post-mitigation test must be done to ensure that the mitigation steps were successful.  In some cases secondary or tertiary mitigation steps must be taken to achieve a reading below 4.0pCi/l.  If for example your initial test reading was 8.0pCi/l and the first mitigation effort reduced the radon by 25%, Post-Mitigation test #1 may indicate a 25% drop but that’s still 6.0pCi/L.  A second mitigation system may have to be added which may reduce the radon by another 25%.  6.0pCi/L less 25% is only a 1.5pCi/L reduction so you STILL may be above 4.0pCi/L.  A third mitigation system may be necessary to finally get you below 4.0pCi/L.


Radon is a serious health issue but it can be minimized.  Likely, it cannot be eliminated.  It’s naturally occurring and exists in nature.  It’s not man-made nor can we stop it from existing.  We can, however, minimize its pathways into our homes and help ensure a healthy and safe environment.

Please call today to schedule your  radon test for your family.  Discounted prices are valid for tests started by February 28, 2014.  Please mention, “Radon Discount” when you call.  Also, if you need radon consultation, Regal Home Inspections, LLC can help guide you through the testing and mitigation process.

I would appreciate your comments about this article.  Please email your comments to .