Radon Questions & Answers

Most Colorado radon mitigation systems cost between $1,000 and $2,800, with the median residential install around $1,400. Sub-slab depressurization (the most common method) typically runs $800-$2,200; crawl space sub-membrane systems run $1,500-$3,500. Cost varies based on foundation type, basement size, radon source location, and accessibility for venting routes.

Colorado has one of the highest indoor radon levels in the United States. According to the Colorado Department of Public Health and Environment (CDPHE), about half of all Colorado homes test above the EPA action level of 4 pCi/L, and the statewide indoor average is roughly 6.4 pCi/L — nearly five times the U.S. average of 1.3 pCi/L. The cause is geological: uranium-bearing granitic bedrock and soils across the Front Range and Rocky Mountains release radon that accumulates in basement-heavy housing. Cold Colorado winters intensify the problem through the stack effect — heated indoor air rising pulls radon-laden soil gas into the home.

Most Colorado residential radon mitigation installs complete in 4-8 hours of on-site work. Sub-slab depressurization typically takes 4-6 hours; crawl space sub-membrane systems take 6-10 hours including vapor barrier installation. Post-installation verification testing requires an additional 48-96 hours to confirm the system has reduced radon below the EPA action level.

Yes — properly installed active radon mitigation systems reduce indoor radon by 50-99%, with most Colorado installs achieving final readings below 2 pCi/L (well below the EPA action level of 4 pCi/L). Independent post-mitigation verification testing confirms system effectiveness within 48-96 hours of activation. AARST-ANSI standard installs have a 99%+ success rate when verified post-install.

Colorado does not require sellers to test for radon, but Colorado law does require disclosure of any known radon test results to buyers. In practice, most Colorado real estate transactions in 2026 include a radon contingency, and buyers commonly request radon testing as part of inspection. Sellers who test and mitigate proactively often close faster and avoid renegotiation.

Test first. The only way to know your radon level is to test. EPA recommends short-term tests (2-7 days) for initial screening and long-term tests (90+ days) for confirmation. If results exceed 4 pCi/L, EPA recommends mitigation. If results are between 2-4 pCi/L, EPA recommends considering mitigation given Colorado's high background levels. Most Colorado homeowners should test every 2 years and after any major foundation work.

Colorado requires radon mitigation contractors to hold BOTH national NRPP (National Radon Proficiency Program) certification AND state Colorado Department of Public Health and Environment (CDPHE) registration. The contractor should also carry general liability insurance of at least $1M and follow AARST-ANSI installation standards. You can verify NRPP certification at nrpp.info and Colorado state licensing through the CDPHE Radon Program (303-692-3442).

Radon testing measures the radon level in your home — typically using a 2-7 day short-term test or 90+ day long-term test. Radon mitigation is the installation of a system to reduce elevated radon levels. You test first to determine if mitigation is needed; mitigation is the engineering solution if test results exceed the EPA action level of 4 pCi/L.

Yes. Radon is the second-leading cause of lung cancer in the United States after smoking, responsible for approximately 21,000 deaths annually according to the EPA. Colorado's high radon levels mean Coloradans face elevated lung cancer risk compared to other states. Children, smokers, and people with respiratory conditions face proportionally higher risk from chronic radon exposure.

The piping and structural components of an Colorado radon mitigation system typically last 20+ years. The radon fan (the active component) has a typical lifespan of 5-10 years depending on the model and continuous operation. Fans should be tested annually and replaced when failed. The overall system should be verified with a follow-up radon test every 2 years.

Colorado Radon Experts is a lead-routing service that connects Colorado homeowners with NRPP-certified and Colorado DORA-licensed radon mitigation specialists across 22 Colorado cities. We do not perform radon testing or mitigation directly — all work is performed by our certified partner contractors operating under their own licensing and insurance. We're the marketing and qualification layer; the partners are the trade professionals.

Colorado state law requires that radon mitigation work be performed by an CDPHE-licensed contractor. DIY radon mitigation kits exist but are illegal to use for compliance purposes in Colorado, void most real estate transaction requirements, and rarely achieve the reduction performance of professionally-installed systems. For real estate transactions, lender requirements, or insurance purposes, professional installation is required.

A standard active sub-slab depressurization system is installed in 4-8 hours: (1) a 3-6 inch suction hole is cored through the basement slab; (2) a PVC vent pipe is run from that suction point up through the house or along an exterior wall; (3) an inline radon fan is mounted in the attic or outside — never in livable space; (4) the pipe is vented to discharge at least 10 feet above grade and at least 10 feet from any window, door, or opening; (5) slab cracks and penetrations are sealed to improve suction; (6) a manometer (U-shaped pressure gauge) is mounted so you can confirm the system is running; (7) a post-install verification test (48-96 hours) confirms the radon level dropped. About 90% of Colorado installs use this method.

Sub-slab depressurization (also called active soil depressurization, or ASD) is the standard radon mitigation method: a continuously-running fan creates suction underneath your concrete slab, intercepting radon gas before it enters the home and venting it safely above the roofline. Because the pressure under the slab is now lower than the air pressure inside the house, soil gas flows out the pipe instead of up into your living space. It's the most common approach — used in 90%+ of installs — and reduces radon by 50-99%.

A finished system is mostly a single 3-4 inch white PVC pipe running from the basement floor up and out of the house, plus an inline fan. How visible it is depends on routing: an exterior run puts the pipe and fan on an outside wall (most affordable, more visible), while an interior run hides the pipe through a closet, garage, or chase and places the fan in the attic (cleaner curb appeal, sometimes higher cost). The only indoor evidence is usually a small manometer gauge on the pipe. Most homeowners find it unobtrusive once routed thoughtfully.

By code and standard practice, the radon fan is never installed inside a livable space or basement — it goes in the attic or outside, so that any leak in the pressurized section discharges outside the home rather than into it. The vent discharges at least 10 feet above ground level and at least 10 feet away from any window, door, or other opening so the exhausted radon disperses and cannot re-enter. The pipe itself can run inside (through a closet or garage) or along an exterior wall depending on your preference for appearance versus cost.

Clear access to the basement area where the suction point will go and to the planned pipe route (attic, closet, or exterior wall). On install day a crew is on site 4-8 hours — a single day for most basements; crawl spaces can take 1-2 days. They core the slab, run and seal the pipe, mount the fan and manometer, and activate the system. You don't need to leave the home. About 48-96 hours later, a verification test confirms the radon level dropped below the EPA action level of 4 pCi/L.

A properly designed system almost always succeeds — active systems cut radon 50-99%, and most Colorado installs reach below 2 pCi/L, well under the 4.0 action level. AARST-ANSI-standard installs succeed 99%+ of the time when verified. If a verification test still shows an elevated level, the contractor adjusts the system — adding suction points, upsizing the fan, or sealing additional entry routes — until it passes. Ask any contractor before hiring what they do if the first test doesn't pass; reputable installers stand behind the result.

An active system runs continuously, so as long as the fan is operating, radon stays suppressed — it does not 'come back' while the system works. Levels can rise again only if the fan fails, the pipe is damaged, or new foundation cracks open over time, which is why you check the manometer and re-test every 2 years. A failed fan is the most common cause and is a straightforward repair.

Partner contractors typically provide a 5-year warranty on the radon fan and a lifetime warranty on the PVC piping, though terms vary by installer. Warranty specifics are set by the installing contractor, so ask for them in writing on your quote. A written warranty plus a post-install verification test are two of the most important things to confirm before hiring.

It's negotiable and usually handled like any other inspection finding. When a radon test during the inspection period comes back elevated, the buyer commonly requests that the seller pay for mitigation or credit the cost at closing — but who ultimately pays depends on the purchase agreement and the local market. Because a typical Colorado system is $800-$2,500, it's a relatively small line item in most deals, and sellers who mitigate proactively often avoid renegotiation.

For real-estate deadlines, installs can usually be expedited to a 7-14 day turnaround. Tell us it's tied to a closing when you reach out — partner contractors prioritize transaction-driven jobs because the inspection contingency window is tight. The system itself installs in 4-8 hours, and the confirming verification test runs 48-96 hours after activation, so plan for that window before closing.

No state permit is required to install a radon mitigation system in Colorado. However, the work must be performed by an NRPP- (or NRSB-) certified contractor who is registered with the Colorado Department of Public Health and Environment (CDPHE) to be done legally and to AARST-ANSI standards. Local building departments may have their own electrical requirements for the fan wiring or roof-penetration rules, so a qualified contractor handles any local permitting that applies.

If you're building, it's far cheaper to install radon-resistant features during construction than to retrofit later. RRNC typically means laying a gas-permeable layer and vapor barrier under the slab plus a capped vent pipe (a passive stub), so that if a post-construction test is high, a fan can be added to activate the system with minimal work. Colorado is in EPA Radon Zone 1, where RRNC is especially worthwhile. We can connect builders with a specialist who installs these systems.