How to Find and Vet a Radon Mitigation Contractor

Your test came back high. You know you need a mitigation system. Now comes the part that trips a lot of homeowners up: finding someone trustworthy to install it.

The good news is there are excellent radon mitigation contractors in most parts of the country. The less good news is there are also a handful of unqualified people charging real money for work that may not actually fix your problem. This guide walks you through exactly how to find a qualified contractor, what questions to ask before you hire, and what red flags to walk away from.

🏅Why certification matters

Radon mitigation is not a licensed trade in every state, which means technically, anyone with a van and a fan can call themselves a radon contractor. That is exactly why certification exists.

The two main national certification programs are:

• •NRPP (National Radon Proficiency Program): run by AARST (American Association of Radon Scientists and Technologists). Widely recognized, with rigorous exam and continuing education requirements.
• •NRSB (National Radon Safety Board): also nationally recognized, with similar standards. Accepted in all states.

Some states, including Illinois, Iowa, and Tennessee, require state-specific licensing on top of national certification. Your state radon office can confirm what is required where you live.

🔍Where to find certified contractors

Start with the official directories, then layer in local research:

• •AARST-NRPP Contractor Finder. Visit aarst-nrpp.com and search by zip code or state. Profiles show certification status, expiration date, and contact info.
• •NRSB Directory. Visit nrsb.org and use the "Find a Professional" search.
• •Your state radon office. Every state has one (usually within the state health or environment department). Many maintain their own referral lists.
• •Real estate referrals. If you recently bought a home, your agent likely has a list of local contractors vetted through repeat business.
• •Neighbors and neighborhood groups. If you are in a high-radon area, someone nearby has been through this recently.

❓Questions to ask before you hire

Get at least two or three quotes. During those calls, here are the questions worth asking:

Certification and experience

• •"Are you NRPP or NRSB certified, and can you share your certification number?"
• •"How long have you been installing mitigation systems in this area?"
• •"Do you carry liability insurance and workers' comp?"

The system and the quote

• •"Will you do a diagnostic before giving a final quote, or is the estimate based on a site visit?"
• •"What type of system do you recommend for my home, and why?"
• •"What is included in the quoted price: labor, materials, fan, post-installation testing?"

After the job

• •"Do you include post-mitigation testing to confirm the system worked?"
• •"What kind of warranty do you offer on the fan and the installation?"
• •"If the first post-install test still comes back above 4 pCi/L, what is your process?"

🚩Red flags to walk away from

Most radon contractors are legitimate. But here are the warning signs that should give you pause:

• •No certification or vague about it. If they cannot give you a certification number to verify, move on.
• •Pressure to decide immediately. High-pressure sales tactics are not how trustworthy contractors operate.
• •Unusually low bids. A sub-$500 quote for a full system in a larger home should raise questions. Cutting corners on fan quality or installation costs you more later.
• •No post-installation testing offered. Any reputable contractor tests the home after installation. If they do not offer this, ask why.
• •Guarantees of a specific radon level. A good contractor can promise to reduce levels significantly, but no one can guarantee an exact number. That claim is a sales technique.
• •No written contract. Every job should come with a written scope of work, price, warranty terms, and recourse if the system does not perform.

🏗️What to expect on installation day

A standard sub-slab depressurization installation for a typical home takes about half a day, usually three to five hours. Here is what normally happens:

• •Inspection and diagnostic. The contractor checks your foundation type, looks for cracks or sump pits, and may run a suction test to determine optimal placement.
• •Core drilling. A hole is drilled through the slab to create the suction point, with a small pit dug beneath it to maximize airflow.
• •Pipe routing. PVC pipe runs from the suction point up through the house or along the exterior wall, ending above the roofline.
• •Fan installation. The radon fan is installed in the pipe run, typically in the attic or on an exterior wall. It runs continuously and is designed to last 10–20 years.
• •Sealing. Cracks and any openings in the slab are sealed to improve system efficiency.
• •Post-installation walkthrough. The contractor explains the system, shows you the visual indicator (a small u-tube confirming negative pressure), and schedules the follow-up test.

🧪After installation: test, then test again

Do not assume the system worked just because it is running. EPA guidelines recommend testing within 24 hours to 30 days after installation. Most reputable contractors include a short-term test. If yours does not, run one yourself. A charcoal kit costs around $15 and gives results within a week.

The goal is to confirm levels are below 4 pCi/L. Most well-installed systems get homes to 1–2 pCi/L or lower. If your follow-up test still shows elevated levels, contact your contractor. Any reputable one will come back and adjust.

After that, the EPA recommends retesting every two years and after any major renovation to your foundation.