Before you hire

Ask for the credential number as it appears on the contract — hard to reverse later

A claim of being licensed is not a number you can check.

Confirm it is current with the issuing agency, not just once-held — hard to reverse later

Credentials lapse. The agency for your state is named on its resource centre page.

Confirm it covers mitigation, not measurement alone — hard to reverse later

These are separate credentials everywhere both exist, and one does not authorise the other.

In a state without radon licensing, verify NRPP or NRSB certification directly — hard to reverse later

With no state register, the national certification is the credential rather than a supplement to one.

Ask for proof of insurance

Documentation rather than assertion.

Insist on a site visit before a price on anything other than a simple poured basement — hard to reverse later

A phone quote on a mixed-foundation house is a guess, and the change order is the usual consequence.

Ask whether a sub-slab diagnostic is included, and what it measures — hard to reverse later

Pressure field extension determines suction-point count and fan sizing. Without it, both are assumptions.

Ask which soil-contact zones the price covers — hard to reverse later

A quote that omits a crawl space or a slab addition has priced a different house.

Suction point count and locations, marked — hard to reverse later

The single largest driver of both price and outcome.

Routing path and where the discharge terminates — hard to reverse later

Discharge above the roofline away from windows is a standard requirement and a common shortcut.

Sealing scope: floor-wall joint, penetrations, sump lid, floor drains

Unsealed openings let the fan pull room air instead of soil gas.

Fan make and model, and where it will be mounted

Mounting must be outside conditioned living space, and accessibility governs future replacement cost.

Electrical responsibility and who pulls any permit — hard to reverse later

A local question. Ambiguity here is how a homeowner inherits a permit problem.

The post-mitigation verification test, inside the price — hard to reverse later

This is the deliverable. Its absence is the most common reason a cheap bid is cheap.

What happens if verification comes back above the action level — hard to reverse later

A named remedy turns a bad outcome into a procedure. Silence turns it into a negotiation with someone already paid.

Ask which of the three you are getting: equipment, workmanship, or an outcome commitment — hard to reverse later

These are different instruments and are routinely spoken about as one.

Ask who administers a warranty claim and whether labour is included

This is where people discover the gap too late.

Ask whether the warranty transfers on sale

A transferable warranty is a genuine asset at resale.

Ask what voids it

Basement finishing after installation is common enough to be worth settling in advance.