You're under contract on a Colorado home. The inspection report just came back showing radon above the EPA action level. You have an inspection objection deadline approaching, a closing date locked in, and now a decision tree to navigate.
The short answer: most Colorado mitigation systems can be installed in 7–10 days end-to-end (quote, scheduling, install, post-mitigation test), and a basement install typically runs $1,000–$3,500.[1] Whether you mitigate before closing, ask for a seller credit, or walk depends on your timeline, your contract terms, and how much pressure you're willing to absorb.
This page walks through the Colorado-specific rules, your three buyer options, realistic timelines, and the tradeoffs between mitigating before closing versus taking a credit.
Colorado SB23-206 — the disclosure law you should know
Since August 7, 2023, Colorado law requires sellers of residential property to disclose any known radon test results and any mitigation work performed on the home, along with the CDPHE radon brochure.[2] The disclosure happens through the Seller's Property Disclosure form (revised post-SB23-206) and applies to both sales and residential leases.
What this means in practice:
- If the seller had a prior radon test, you should have seen the result in the disclosure.
- If the seller had mitigation done, you should have the system documentation and post-mitigation test result.
- If you discover elevated radon during inspection and the seller didn't disclose a prior test result, that's a fact pattern worth showing your real estate attorney.
- If you mitigate as a buyer and later sell the home, the system becomes your required disclosure.
Colorado does not require sellers to mitigate before sale.[1] They must disclose; they can sell "as-is."
Your three buyer options under the inspection objection
Option 1 — Ask the seller to mitigate before closing
You request mitigation as part of the inspection objection. The seller hires a Colorado-licensed contractor, installs the system, completes a post-mitigation test, and provides you the documentation before closing.
When this works: Closing is at least 2 weeks out, the seller is motivated to keep the deal alive, and the local contractor pool has openings.
Tradeoffs: You don't control the contractor selection or the install quality. The seller chooses the lowest available bid.
Option 2 — Negotiate a seller credit at closing
The seller credits you a fixed dollar amount at closing — typically $1,500–$2,500 for a basement or $2,500–$4,500 for a crawlspace or multi-zone — and you hire a contractor on your own timeline after you own the home.
When this works: Closing is tight, you want control over the contractor, or you want to bundle mitigation with other post-purchase work (basement finishing, encapsulation).
Tradeoffs: You're exposed to the radon during whatever interval passes between closing and your install. The credit may not fully cover the actual install cost if the home turns out to be multi-zone or crawlspace.
Option 3 — Walk under the inspection contingency
If you have an inspection contingency and you're not willing to take a credit or wait for pre-close mitigation, you can terminate the contract.
When this works: You found something else in the inspection you also don't like, or you're in a buyer's market with comparable homes available.
Tradeoffs: Most Colorado Springs homes will test positive — the next home you go under contract on has a 40%+ chance of the same result.[3] "Walking on radon" alone is usually only the right call when you've also found a non-radon issue.
How long mitigation actually takes
End-to-end, a Colorado Springs mitigation install typically runs 7–10 days:
| Step | Typical time |
|---|---|
| Quote (in-home assessment + written quote) | 1–3 days |
| Scheduling install | 3–7 days out |
| Install (single day) | 4–8 hours on site |
| Post-mitigation test wait (24h fan run, then 2–7 day test) | 3–8 days |
| Test result + system certification | 1–3 days |
If you're in a 14-day inspection objection window and closing 30 days out, pre-close mitigation is comfortable. If you're closing in 10 days, it's tight but doable. Closer than that, a seller credit is usually the cleaner path.
Mitigate before close vs after close — the tradeoffs
| Mitigate before close | Credit + mitigate after close | |
|---|---|---|
| Who picks the contractor | Seller | You |
| Quality control | Seller's preference | Your choice of bids |
| Documentation | Belongs to seller, transferred to you | Belongs to you from day one |
| Timing | Must finish before closing date | Your schedule |
| Cost certainty | Closing is contingent on a final post-mit test | Credit is fixed at closing |
| Exposure during install gap | None (system in before you move in) | You live with radon until install |
Cost ranges for closing-deadline mitigations
Real estate deadlines sometimes carry a small premium for guaranteed completion scheduling — but the baseline pricing is the same as a non-rushed install. Use the four-scenario framework:
- Basic basement: $1,000–$2,000 (CDPHE baseline)
- Finished basement: $1,500–$3,000
- Crawlspace: $2,000–$4,500
- Multi-zone: $2,500–$5,000
If you're negotiating a seller credit, those are reasonable numbers to anchor on. A credit at the high end of the appropriate scenario gives you room for a quality contractor without surprises.
A buyer under contract on a 1990s tri-level home in Stetson Hills receives an inspection report showing 6.7 pCi/L. The seller's prior disclosure showed no test result. The buyer has 5 days remaining on their inspection objection and 18 days to closing. After consulting their agent, the buyer asks for a $3,000 seller credit at closing rather than asking the seller to mitigate (tri-level means multi-zone, and the buyer wants to control contractor selection and diagnostic scope). The seller agrees. After closing, the buyer takes two written quotes — both proposing a PFE diagnostic and two suction points — and installs the system in week three of ownership. The post-mitigation test comes in at 2.1 pCi/L. The buyer's documentation (test report, quotes, install paperwork, post-mit test) becomes part of their own future SB23-206 disclosure if they ever sell.
What to keep for future disclosure
If you mitigate (or inherit a mitigation system from the seller), keep these documents permanently. They become your required SB23-206 disclosure when you eventually sell:
- Original test report (the high reading that triggered mitigation)
- Contractor's written quote and final invoice
- System certification, DORA license verification, fan model and warranty paperwork
- Post-mitigation test result certificate
- Any retest results going forward (EPA recommends every 2 years)[4]