What Is Radon Mitigation?

Radon mitigation is the process of reducing radon gas concentrations in the air inside a building. Radon is a naturally occurring radioactive gas that seeps into homes through cracks and openings in foundations. You can’t see it, smell it, or taste it — but long-term exposure is the second leading cause of lung cancer in the United States, responsible for approximately 21,000 deaths per year according to the EPA.

Mitigation systems work by intercepting radon before it enters your living space or by ventilating it out after it does. The most common approach — sub-slab depressurization — uses a fan and pipe system to draw radon from beneath the foundation and vent it safely above the roofline, where it disperses harmlessly into the outdoor air.

The good news: radon mitigation is highly effective. A properly installed system can reduce indoor radon levels by up to 99%, and most installations are completed in a single day.

How Radon Enters Your Home

Radon is produced by the natural decay of uranium in soil, rock, and water. It moves upward through the ground and enters buildings through any opening where the structure contacts the soil.

Common entry points include:

Foundation Cracks

Even small cracks in basement floors and walls provide pathways for radon. Homes settle over time, and virtually every poured concrete or block foundation develops some degree of cracking.

Construction Joints

The joint where the basement floor meets the wall — called a cove joint — is one of the most common radon entry points. Cold joints in poured concrete are another frequent source.

Gaps Around Pipes and Utilities

Openings where plumbing, electrical conduits, and other utilities penetrate the foundation allow radon to bypass the slab entirely.

Sump Pits

Uncovered or improperly sealed sump pits provide a direct pathway from the soil beneath your home into the basement air.

Crawl Spaces

Homes with dirt-floor crawl spaces have essentially no barrier between the soil gas and the living space above.

Radon levels can vary dramatically from one home to the next — even neighboring houses can have very different concentrations. That’s why every home needs its own test, regardless of what your neighbors’ results show.

How Radon Mitigation Systems Work

The goal of every mitigation system is the same: create a pressure difference that prevents radon from entering the home. Several methods exist, and a certified professional will recommend the right approach based on your home’s foundation type, construction, and radon levels.

Sub-Slab Depressurization (Most Common)

Sub-slab depressurization (SSD) is the most widely used and effective radon mitigation method. It works by:

Drilling a small hole (typically 4–5 inches) through the basement floor slab

Installing a PVC pipe from below the slab up through the house and out above the roofline

Attaching a radon fan that runs continuously, creating suction beneath the slab

The fan pulls radon-laden soil gas from under the foundation and exhausts it above the roof, where it dilutes safely in outdoor air

This method is effective because it reverses the natural air pressure dynamics that draw radon indoors. Instead of your home pulling soil gas in, the fan pulls it away before it can enter.

Most SSD systems use a 3-inch or 4-inch PVC pipe and a fan rated between 20 and 90 watts. The pipe can run through a closet, garage, or along an exterior wall. Exterior installations are common when interior routing isn’t practical.

Sub-Membrane Depressurization (For Crawl Spaces)

For homes with crawl spaces, a heavy-duty polyethylene sheet is sealed over the dirt floor and up the walls. A fan and pipe system then draws radon from beneath the membrane, similar to how sub-slab systems work.

This approach is sometimes combined with crawl space encapsulation for added moisture and air quality benefits.

Drain Tile Suction

Some homes have existing drain tile systems (interior or exterior) around the foundation footer. A radon fan can be connected to these drain tiles to draw radon from the soil and vent it outdoors. This is often effective and minimizes the need for additional penetrations through the slab.

Block Wall Suction

Homes built with hollow concrete block foundations may accumulate radon inside the block cavities. Block wall suction uses a fan to depressurize the interior of the block walls, preventing radon from escaping into the basement.

Heat Recovery Ventilators (HRVs)

In some cases — particularly when radon levels are only moderately elevated — a heat recovery ventilator can dilute indoor radon by exchanging indoor air with outdoor air while recovering most of the heat energy. HRVs are less common as a standalone solution and are typically used as a supplement.

What to Expect During Installation

Radon mitigation installation is straightforward and minimally disruptive. Here’s a typical timeline for a standard sub-slab depressurization system:

Before Installation

Your contractor will evaluate your home’s foundation type, layout, and radon test results. They may inspect the basement, crawl space, and exterior to determine the best pipe routing and fan placement.

Installation Day (4–8 Hours)

The installer drills a suction point through the slab, installs PVC piping from the sub-slab area to above the roofline, mounts the radon fan, seals cracks and openings in the foundation, and installs a U-tube manometer (a simple gauge that confirms the system is creating suction).

The process typically takes 4 to 8 hours for a standard home. There is minimal dust, and the work area is cleaned up the same day. You do not need to leave your home during installation.

After Installation

The system runs continuously. The fan draws very little power — typically $50 to $150 per year in electricity costs. The U-tube manometer on the pipe provides a quick visual check that the system is operating. If the fluid levels are uneven, the fan is working.

A follow-up radon test should be conducted 24 to 48 hours after installation and at least 12 hours after the system has been running. This confirms that radon levels have dropped below the EPA action level of 4 pCi/L. Most properly installed systems reduce levels to below 2 pCi/L.

Radon Mitigation Cost

The typical cost for a standard sub-slab depressurization system ranges from $800 to $1,500. Most homes in Maryland and Pennsylvania fall within this range.

Several factors affect the final price: home size, foundation type, number of suction points needed, pipe routing complexity, and whether the system is interior or exterior mount.

Homes with complex layouts, multiple foundation types, or very high radon levels may require additional suction points or higher-capacity fans, which can increase the cost to $1,500–$2,500.

The investment pays for itself in long-term health protection. When you consider that the average radon mitigation job eliminates a serious cancer risk, $800–$1,500 is a fraction of what most homeowners spend on far less critical home improvements.

See our full radon mitigation cost breakdown →

How to Find a Qualified Radon Mitigation Contractor

Not all radon contractors are equal. Here’s what to look for:

Certification

Look for contractors certified by the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB). These are the two nationally recognized certification bodies. In Pennsylvania, radon mitigation contractors are required by law to hold state certification through the PA Department of Environmental Protection (DEP).

Maryland does not currently require state-level radon certification, which makes national certification even more important when choosing a contractor in MD.

Insurance and Warranties

A reputable contractor carries general liability insurance and offers a written warranty on both parts and labor. Most quality contractors provide a performance guarantee — meaning they warrant that the system will reduce radon levels below the EPA action level.

Experience and Reviews

Check Google reviews, ask for references, and look for contractors who specialize in radon rather than offering it as a side service. A contractor who does radon mitigation as their primary business will have more experience with difficult installations.

The RadonSafetyGuide.com Approach

RadonSafetyGuide.com pre-screens contractors for NRPP or NRSB certification and connects you with one qualified professional — not five competing companies. You submit one form, get one call, and make your decision without pressure.

Radon Mitigation in Maryland and Pennsylvania

Maryland and Pennsylvania have some of the highest radon levels in the country. The EPA classifies large portions of both states as Zone 1 — the highest-risk designation for indoor radon.

Maryland

Frederick County, western Maryland, and parts of central Maryland have consistently elevated radon levels. The average indoor radon level in Frederick County is approximately 8.29 pCi/L — more than double the EPA action level. Even areas that aren’t traditionally considered high-risk can have individual homes with dangerous levels.

Maryland does not require state certification for radon professionals, so homeowners should verify that their contractor holds NRPP or NRSB certification independently.

Pennsylvania

Pennsylvania has some of the highest radon levels in the nation. Approximately 40% of homes tested in Pennsylvania exceed the EPA action level of 4 pCi/L. The Lehigh Valley, Reading, Lancaster, York, and Harrisburg areas are particularly affected.

Pennsylvania requires state certification for all radon testing and mitigation professionals through the PA DEP. Mitigation contractors hold a 7000-series certification number.

Whether you’re in Maryland or Pennsylvania, the first step is always a radon test. If your results are at or above 4 pCi/L, mitigation is recommended.

Get a free radon quote in Maryland or Pennsylvania →

Verify Your Radon Levels

Whether you’re considering mitigation or want to verify your system is working, accurate testing is essential.

Airthings Corentium Home 2 — Monitor radon levels continuously before and after mitigation. See real-time results. (~$180)

SunRADON Lüft — Wi-Fi connected radon monitor with app alerts. Designed specifically for verifying mitigation system performance. (~$169–$199)

Buy from SunRADON — use code HEALTHYAIR for a discount

Buy direct from Airthings — save 10% with code RADONSAFETY-10OFF | Also available on Amazon

First Alert Radon Gas Test Kit, RD1 — Simple, lab-analyzed short-term test for a quick reading. (~$15)

As an Amazon Associate, RadonSafetyGuide.com earns from qualifying purchases. We also participate in the Airthings affiliate program.

Get a Free Radon Mitigation Quote

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Frequently Asked Questions About Radon Mitigation

Find Radon Mitigation Near You

RadonSafetyGuide.com connects homeowners with certified radon mitigation professionals across Maryland. Select your area below to learn about radon risks in your community and request a free quote from a local pro.

Frederick County, MD

Radon Mitigation in Frederick, MD · Thurmont · Middletown · Brunswick · Walkersville · New Market

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Radon Mitigation in Westminster, MD · Mount Airy

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Radon Mitigation in Gaithersburg, MD · Rockville

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