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How to: Check for Radon Gas in Your Home

The best way to ensure you get an accurate test is to call a Radon professional. If you are buying a home, then a professional test is the way to go. It’s also required under most real estate contracts.

If you are more adventurous and want to conduct a test on your own, some good testing options are available online and at the local home store. Some states even offer free test kits under certain circumstances. Buying a test kit can cost as little as $10.00; however, it may not include the lab fee, so be sure to read the fine print before you buy.

See here if you live in Maryland, Pennsylvania, or Delaware for more details on free testing!

Basics of radon testing:


All homes and apartments should be tested whether they are on a slab or on the higher floors of a multi-story building. The cost to test is low, and the danger of exposure is high.

The test should be in the lowest level of the home you use; for a real estate transaction, place the test in the lowest level that could be used.

All test devices must be placed more than 20 inches off the floor and less than 8 feet in height.

The distance from the side wall is a minimum of 1 foot, and if a window or door is located on that wall, you should place the device(s) at least 3 feet away.

How long?

The shortest test that you can run is 48 hours. Some devices have upper limits, i.e., 7 days is the limit for charcoal. Be sure to carefully read all instructions.

All tests are good for at least 48 hours, and most tests can be run longer or up to 7 days.

Long-term testing options are good for more than 90 days and are a good choice if your levels are close to the cut-off of equal to or higher than 4 Pci/L. Long term testing would not be my choice for my first test, simply because if I ran a short term and it tested significantly elevated, I would want to limit my exposure time.

Test Conditions?

Closed house conditions should be met 12 hours prior to the start of the testing period. All doors and windows in the entire home should remain closed as much as possible, and fireplace dampers or glass doors on the fireplace should be closed. Do not run fans for long periods that vent to the outside. Remember not to open windows because even a short time can affect the results.

For active devices, there is a ramp-up period. The device reports both short term and long term results. The long term usually reflects 7 days of data. I would pay most attention to the long term results.

Weather can affect the results. For example, heavy rain and high winds can throw off the results and often elevate radon levels for a short time. The reason for longer testing is that radon levels change over the course of the day. That’s why we need a 48 hour sample to better understand the average levels.


Active – An electronic device that measures radon.

Passive – A device using a charge plate, charcoal, or liquid.


A professional test


Passive store kit or State kit


Active test devices


*above is a quick internet search.


What if the result levels are equal to or higher than 4 pCi/L? If the result levels are over 4pCi/L and under 10pCi/L, you may want to consider a long term test.

Suppose 2 passive home tests confirm the radon level or one active device indicates that the levels need to be reduced. In that case, you need to find a professional to bid the work.

You should check the professional’s credentials with your local State agency.

If you choose to take this job on yourself, make sure you follow EPA Guidelines and avoid worsening your problem by inadvertently pumping the radon back into the house, as we have seen done.

What is a radon mitigation system?

The main job of radon mitigation, or reduction, is to change how the pressure works under the home. The soil around your house is heavier than air, and the radon in that soil would like to go to the lower pressure in your basement. Our job is to make a small part of the underside of the slab in the basement or floor of the crawlspace much lower pressure than the surrounding soil coaxing the radon into piping we place and through a fan to a pipe above the eaves of your home where it is safely exhausted away.

This works differently for each house, so there is no way to say how much a system will reduce the radon levels until it is installed.

Bigger fans can make a difference, and more suction points can make a difference, as can the soil type and the age of the home.

The risk?

According to the EPA, exposure to radon gas is the number 2 cause of lung cancer. This is both true and scary. If you do not smoke, exposure to radon gas is the number 1 cause of lung cancer. However, if you smoke indoors, you are 15 times more likely to get cancer than if you don’t smoke inside.

In conclusion, we have been in the radon business for more than 25 years. Exposure to elevated levels of radon gas is real and causes misery. Radon gas can be tested for free in some states, or a home kit costs a few dollars. Reducing radon in a home ranges from $1,000 to $5,000 for residences with large crawlspaces or other items that make installation difficult. On average, we see about $1,300 to remediate.

If you'd like to schedule a radon test or reduction with us please call (302) 993-9100!

You can also check out our radon testing page or our radon mitigation page!

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