Step By Step

How Radon Mitigation Works

1. Testing

A short-term test (2–90 days) or long-term test (over 90 days) measures radon concentration in pCi/L (picocuries per liter). The EPA recommends acting if a result comes back at or above 4 pCi/L, though it notes there's no fully "safe" level and levels between 2 and 4 pCi/L are worth considering too. For how to choose and run a test, see radon testing in York County, PA.

2. System design

A PA DEP-certified mitigator inspects the foundation type, basement, crawlspace, slab-on-grade, or a mix, and designs a system around it. Foundation type is the single biggest factor in system cost and complexity.

3. Installation

The most common method is active soil depressurization: a PVC pipe is run from beneath the slab (through a small hole cored in the foundation) up through the house and vented above the roofline, with an inline fan drawing radon-laden air out and venting it where it disperses safely outdoors instead of building up indoors. Cracks and openings in the foundation are also sealed to reduce the paths radon can enter.

4. Post-mitigation testing

Once the system is running, a follow-up test confirms the level has actually dropped below the action threshold. This is the step that verifies the job worked, rather than just assuming it did.

Step by step, with what you should have in hand at each stage

1. The test, and the number

Nothing starts without a result. A short-term kit costs about fifteen dollars and answers the question in two to seven days under closed-house conditions. If the number is between 4 and 8 pCi/L, DEP's guidance is to confirm with either a 365-day long-term test or a second short-term test. Above 8, confirm short-term and move. See short-term vs long-term tests.

2. The site visit and diagnostics

Foundation type, slab condition, where a suction point can realistically go, where pipe can be routed, whether there is existing drain tile or a usable sump. Communication testing, drilling a small test hole and measuring pressure change elsewhere under the slab, is what tells an installer whether one suction point will cover the footprint or whether it needs two. Skipping this is the most common reason a finished system underperforms.

3. The written scope

Before anything is cut you should have, in writing: how many suction points and where, the pipe route and whether it is interior or exterior, the fan model, where the termination goes, what gets sealed, the permit position, and a guaranteed post-mitigation result stated as a number with a defined remedy.

4. Installation

Most single-family homes are a one-day job. Core the slab, excavate the pit, run and support the pipe, mount the fan outside the living space, terminate above the roofline clear of windows, wire the fan with an accessible disconnect, fit the manometer, seal accessible openings and the sump lid, label the system.

5. Verification

A post-mitigation test confirms it worked. That number, not anyone's confidence, is the deliverable. Keep the report, because it is what a buyer's agent will ask for years from now.

6. Handover

You should leave with the post-test result, a photo or note of the manometer's normal reading, the fan model and warranty, and the retest interval. That is the whole maintenance story.

How long each stage takes

Stage	Typical duration
Short-term test	2 to 7 days, plus lab turnaround on some kit types
Confirmation test, if needed	2 to 7 days short-term, or up to 365 days long-term
Site visit and quote	Under an hour on site
Installation	Usually one day for a single-family home
Waiting period before the post-test	At least 24 hours of system operation
Post-mitigation test	2 to 7 days

On a real estate timeline the whole sequence compresses to roughly two weeks, which is why transaction work usually skips long-term confirmation testing entirely.

What we will tell you that other people might not

• If your result is below 4 pCi/L, we will say so rather than selling you a system
• If you have a passive rough-in already, activating it is far cheaper than a new install and we will point at it
• If the number is borderline and nothing is on a deadline, a long-term test is the better next step than a purchase
• If the real problem is a well rather than the foundation, a sub-slab system will not fix it. See radon in well water
• If a second suction point is needed, we will say that before the quote rather than after the first one underperforms

Related: how the standard system works, what changes for an awkward foundation, what it costs.