How to Hire a Radon Mitigator: What to Ask, What to Avoid

Step 1: Verify Credentials Before Anything Else

The radon industry has a certification problem — most states don't require licensing, which means anyone can call themselves a "radon contractor." The way to separate certified professionals from unlicensed operators is to check credentials directly.

National certification bodies:

• NRPP (National Radon Proficiency Program): The most widely recognized certification in the US. Look for the RMT (Radon Mitigation Technician) or RMS (Radon Measurement Specialist) designation. Verify at radonproficiency.org.
• NRSB (National Radon Safety Board): The other major certifying body. Verify at nrsb.org.

A legitimate contractor will have their certification number readily available. If they hedge, can't provide it, or say "I've been doing this for 20 years" instead of showing you a certification number — move on.

State licensing: Some states require additional licensing beyond national certification. Check your state's health department or environmental agency website for state-specific requirements.

Step 2: Get Multiple Quotes

Get at least two quotes, three if you have time. Call each contractor with the same information:

• Your home's foundation type (slab, basement, crawl space)
• Your pre-mitigation radon level (required — they'll need it to recommend the right fan)
• Square footage
• Whether you have a sump pit, finished basement, or crawl space with existing encapsulation

What good quotes include:

• Fan model and specifications
• Pipe routing description (where it enters, where it exits)
• What penetrations will be sealed
• Whether post-mitigation testing is included or charged separately
• Warranty terms on parts and labor
• Performance guarantee language

On price: Pricing varies 20–40% between contractors in the same market. The cheapest quote isn't necessarily bad work — but if it's 50% below the others, ask why. Common explanations for low bids: smaller fan (appropriate for some homes, underpowered for others), no post-mitigation test included, or unlicensed contractor cutting corners on labor.

Step 3: Ask These Questions Before Signing

"Will you do a sub-slab communication test before drilling?"

A quality contractor tests sub-slab airflow before choosing a suction point location. This prevents the most common source of system underperformance. If they skip this step and just drill where it's convenient, you may end up with a system that doesn't adequately depressurize your full slab.

"What fan are you installing, and why that model?"

They should be able to explain fan selection based on your sub-slab conditions, radon level, and foundation size. An XP201 is appropriate for most standard slabs; a GX3 or GX5 is appropriate for packed clay, crawl spaces, or high radon levels. If they're installing the same fan regardless of conditions, that's a concern.

"What's included in the price for sealing?"

The fan and pipe are only part of the job. Sealing the annular space around the pipe, the sump pit (if present), visible slab cracks, and utility penetrations is equally important. Confirm this is included, not an add-on.

"Do you include post-mitigation testing?"

Some contractors include a test kit; others charge separately. Know what you're getting. You want a result in writing — not just the contractor's verbal assurance that "it's working."

"What's your performance guarantee?"

A confident, experienced contractor guarantees their system will reduce levels below 4.0 pCi/L. They should offer to return and adjust the system (at no charge) if post-mitigation testing shows inadequate performance. Get this in writing.

Red Flags to Walk Away From

No certification number. Any legitimate contractor has an NRPP or NRSB number they can provide on request. No number = no hire.

"We don't need to test first." Skipping a pre-mitigation test means they don't know your actual radon level. The post-mitigation result can't be compared to anything, and system sizing may be inappropriate.

Cash only, no contract. The absence of a paper trail protects the contractor, not you. Get a written contract with the performance guarantee before paying anything.

Pressure to decide immediately. Legitimate contractors give you time to compare quotes. High-pressure sales tactics are a red flag in any home service industry.

Installing the fan in living space. Fans should go in the attic, crawl space, or exterior — never in finished living areas. A fan in a bedroom closet or living room is a sign of a poorly designed installation.

No manometer installation. Required by AARST-ANSI standards and by code in most states. If they don't include the warning device, they're cutting corners.

After the Job: Before You Pay

Before issuing final payment, confirm:

1. The fan is running (listen for the hum, check the manometer shows unequal levels)
2. All agreed penetrations were sealed (inspect the core hole — should be filled flush with hydraulic cement)
3. You have the post-mitigation test kit in hand
4. You have documentation of the fan model and warranty

Then run the post-mitigation test. If results come back above 4.0 pCi/L, invoke the performance guarantee before issuing any final payment that remains outstanding.

Find verified certified mitigators in your state →