How to Choose a Radon Mitigation Contractor

Radon mitigation is one of those home projects where the quality of the installer matters as much as the equipment itself. A poorly diagnosed system can leave radon levels barely changed even after you've paid for a full installation. Here's how to vet a contractor before you hire one.

Start with licensing and certification

Radon mitigation oversight varies by state. Some states, including Illinois and Iowa, legally require anyone doing this work to hold a state-issued license, and publish public lists of who currently holds one. Other states don't have their own licensing program but rely on national certification through the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB). Either way, verifying current, active status matters, because licenses and certifications do lapse or get revoked.

• If your state has a licensing program, check the state's public list directly (our state directory links to the official source for states we cover).
• If your state doesn't license radon work, ask the contractor which national certification they hold and confirm it's current, either through NRPP or NRSB's own lookup tools.
• Be wary of a contractor who can't clearly answer which license or certification they hold, or who says it "doesn't matter" in your state. Even where it's not legally required, certification is a meaningful signal of training.

Ask about their diagnostic process

A contractor who quotes a price over the phone without seeing your foundation is guessing. A solid contractor will want to see:

• The foundation type (slab, basement, crawl space, or a mix)
• Whether there's a sump pit, and whether it's currently in use
• Signs of what's under the slab (gravel fill vs. dense soil), sometimes inferred from the home's age and construction style, sometimes confirmed with a small test hole
• Where a vent pipe could realistically be routed to the roofline without cutting through major living space

If a contractor skips straight to a fixed quote without asking any of this, that's worth a follow-up question at minimum.

Get more than one quote

Two or three quotes is a reasonable target, especially if your home has an unusual foundation or a previous mitigation attempt that didn't fully work. Price differences of a few hundred dollars are normal and don't necessarily indicate a problem, but a quote that's dramatically lower than the others is worth asking about directly. Sometimes it reflects a leaner but still adequate system, and sometimes it reflects a contractor planning to cut corners on pipe routing or sealing work.

Questions worth asking directly

• "Is a post-installation radon test included in this price?" A reputable contractor should confirm the system worked, not just that it was installed.
• "What's your warranty, and what happens if the retest doesn't come back below 4.0 pCi/L?" Look for a clear answer, not a vague one.
• "How long have you been doing radon mitigation specifically?" General contractors sometimes add radon work without deep specialization, which isn't automatically disqualifying, but it's useful context.
• "Can I see a recent example of a similar installation, even just a photo?" A contractor proud of their work usually has this on hand.
• "Will you handle the permit if my jurisdiction requires one?" Some areas require a permit for the roof penetration or electrical work involved.

Red flags to watch for

• Pressure to sign same-day, especially paired with a "today only" discount
• Refusal to provide license or certification information
• No mention of a follow-up test, or treating it as optional/extra-cost with no clear explanation of why
• A quote based entirely on square footage with no foundation-specific detail
• No physical business address or a company that's hard to verify beyond a phone number

After the work is done

Keep the paperwork: the contract, the license or certification number, and the post-installation test result. This documentation matters if you sell the home later (see our guide on radon and real estate closings), and it's useful if the system ever needs service, since a future contractor working on it will want to know what was originally installed.

Where to start looking

Radon Mitigation Finder lists licensed and certified contractors pulled directly from official state licensing records, not paid submissions. Every listing links back to the exact government source and the date we pulled it, so you can verify current status yourself before reaching out. Browse contractors by state to get started.