Radon, Mold and Lead: Hiring the Right Specialist for a Denver Rental

General information for Denver-area rental owners, not legal advice. Rules and prices checked October 27, 2026. Cost ranges are published estimates, not quotes.

Radon

Denver sits in EPA's highest radon zone. Since July 1, 2022, anyone doing radon measurement or mitigation for others in Colorado must hold a DORA license. Mitigation professionals must be certified through a national program (NRPP or NRSB) and carry at least $500,000 in professional liability insurance.

The exemptions cover owners working on a home they live in and tenants testing their own unit. Nothing exempts a landlord mitigating a rental they don't occupy, so hire a licensed mitigator. Verify on the DORA license lookup.

Cost: Angi's 2026 Denver guide puts most mitigation jobs at $756–$1,064 (average $899), with active sub-slab systems up to about $2,600.

Disclosure: Colorado landlords must give tenants a written radon disclosure before the lease is signed, with any known test results and the state radon brochure. If a professional test finds 4 pCi/L or more and you don't make a reasonable effort to mitigate within 180 days of notice, tenants on leases longer than a year may be able to void the lease. See our older homes guide.

Lead paint (pre-1978 homes)

Much of Denver's housing was built before 1978. The EPA's Renovation, Repair and Painting (RRP) rule applies to rentals:

• Anyone paid to disturb paint in pre-1978 housing must be an EPA-certified firm using certified renovators. That includes handymen and painters.
• The rule covers jobs disturbing more than 6 square feet of paint per room inside, or 20 square feet outside.
• Window replacement and demolition are always covered, regardless of size.
• Rental property owners and managers are specifically covered.

Colorado administers its own pre-renovation education rule. For covered work in pre-1978 housing, the Renovate Right pamphlet must be given at least 7 days before work starts, with a signed acknowledgment. Lead abatement (permanent removal) is a separate, state-certified specialty.

Ask any painter, handyman or window installer for their EPA RRP firm certificate before work on an older home.

Mold

Colorado doesn't license mold remediators. A bill that would have created a state registry (HB25-1202) didn't pass, and EPA doesn't certify mold firms either. So vetting falls to you: ask about training, insurance, containment methods and post-remediation testing.

The law does set landlord deadlines. Under Colorado's 2024 habitability law, after notice of mold associated with dampness, a landlord must, within 72 hours:

• Install containment.
• Stop active water sources feeding the mold.
• Install HEPA air filtration.

Then, within a reasonable time, the landlord must protect workers and occupants, dry or remove damaged materials, test whether remediation worked, and fix the moisture source. If mold threatens the tenant's health, the tenant can request a comparable unit or hotel room at the landlord's cost.

Practical tip: find a water mitigation company and a mold remediator before you need one. A 72-hour clock doesn't leave time to shop.

How to get help

Good property managers keep licensed radon, mold and lead-safe vendors on their list and know the paperwork each one requires. We'll match you with up to three vetted, licensed managers. Free, no obligation. Get matched free.