Radon in Rental Housing: What to Know
Radon in rental housing is an issue that many tenants and landlords overlook, because radon is invisible and produces no symptoms a renter could notice. Yet renters face the same long-term lung-cancer risk from elevated radon as homeowners do, and they often have less control over testing and mitigation. This guide explains what radon means for rental properties, where responsibility tends to fall, and what tenants and landlords can do. It summarizes EPA and CDC guidance current as of 2026, is educational only, and is not legal or medical advice; consult a certified radon professional for testing decisions and a physician for any health concern.
Part of our Radon Levels guide — start there for the full picture →
Does radon affect rental housing?
Radon affects rental housing exactly as it affects owner-occupied homes. The gas seeps from the soil into any building with ground contact, and apartments, duplexes, single-family rentals, and ground-floor units can all accumulate elevated levels. A renter breathing high radon faces the same cumulative risk as an owner would in the same space.
The EPA recommends that all homes be tested, and that recommendation does not stop at the property line of owner-occupied housing. Ground-contact rental units, especially those on lower floors or over basements and crawl spaces, are prime candidates for elevated radon. Upper-floor apartments far from the soil tend to have lower levels, since radon enters at the base and dilutes as it rises, but lower units share the homeowner’s exposure profile.
The risk is the same because the biology is the same. Radon’s documented harm is long-term lung cancer; the EPA identifies it as a leading cause, and the risk accrues over years regardless of whether you own or rent. A renter cannot feel radon any more than an owner can, which is why testing is the only way to know. Our radon testing guide for Front Range homeowners applies equally to renters living in ground-contact units.
Who is responsible for radon in a rental?
Responsibility for radon in rental housing is a patchwork that depends heavily on state and local law. There is no single national rule that forces landlords to test or mitigate in all private rentals, so the answer varies by where the property sits.
Some states have enacted radon disclosure or testing requirements for rental housing, obligating landlords to inform tenants about radon or to test and mitigate under certain conditions. Other states leave it largely unaddressed, meaning a landlord may have no specific legal duty unless a lease or local ordinance creates one. Federally assisted and public housing has seen increasing attention to radon, with HUD encouraging testing and mitigation in housing it supports.
Practically, landlords own the building and control structural changes, so mitigation, which involves installing systems on the property, is generally a landlord’s domain. Tenants control how they use the unit but cannot install a sub-slab system themselves. Where the law is silent, the lease and a cooperative conversation often determine what happens. Tenants concerned about radon should review their lease, check their state’s rules, and raise the issue with the landlord in writing.
The Colorado context
Colorado’s Front Range has elevated radon potential, so the question is far from academic for renters in Denver, Boulder, Jefferson, and surrounding counties. Colorado has taken steps to address radon in rental housing through disclosure expectations, and tenants here have particular reason to ask about testing given the regional geology. Renters should consult current state and local resources, since rules evolve.
What tenants can do about radon
Renters are not powerless, even when they cannot mitigate on their own. The first step is testing, which a tenant can often do inexpensively with a short-term test kit or a continuous monitor placed in the lowest occupied space. Knowing the number is the foundation for any conversation with a landlord.
If a test shows a level at or above the EPA action level of 4 pCi/L, the tenant has concrete information to bring to the landlord, ideally in writing, requesting professional confirmation and mitigation. The EPA recommends acting at or above 4 pCi/L and suggests considering action between 2 and 4 pCi/L, since risk continues below the action level. Documenting the request and the result protects the tenant and creates a record.
Tenants should also understand their local rights. Some jurisdictions give renters specific recourse regarding radon; others rely on general habitability principles. A tenant facing an unresponsive landlord may consult local housing authorities or tenant-rights resources to understand their options. Throughout, the tenant’s safest course is to test, document, and communicate clearly rather than assume the unit is safe. Our explainer on radon exposure helps renters understand how concentration and time combine into risk.
What landlords should consider
For landlords, addressing radon is both a safety matter and, increasingly, a legal and reputational one. Proactively testing ground-contact units and mitigating where levels are elevated protects tenants from a documented health risk and reduces liability exposure should a tenant later raise concerns.
Testing is inexpensive relative to the stakes, and mitigation through sub-slab depressurization is a well-established, effective fix. A landlord who tests, mitigates where needed, and retains records demonstrates good faith and meets the spirit of public-health guidance even where the law does not strictly compel action. In states with disclosure or testing mandates, compliance is not optional.
Landlords should also factor radon into renovations and turnovers. Sealing a sump pit, installing a passive radon system during construction, or activating an existing system are practical measures. For multi-unit buildings, testing representative ground-contact units helps identify where attention is needed. Treating radon as part of routine property stewardship is simpler and cheaper than reacting to a complaint or a regulatory action later.
How mitigation protects renters
When a rental tests high, the remedy is the same proven approach used in owner-occupied homes. Sub-slab depressurization uses a vent pipe and fan to draw radon from beneath the foundation and exhaust it above the roofline before it enters the unit. Properly installed systems routinely bring levels well below the 4 pCi/L action level, protecting every occupant.
Because mitigation addresses the source, it benefits current and future tenants alike, which is part of why it is a landlord’s responsibility in practice. After installation, a follow-up test confirms the system works, and a continuous monitor can provide ongoing assurance that the fan keeps running, since radon systems can fail quietly. Our overview of the radon mitigation system describes how these components function.
For Front Range renters and landlords, the message is consistent: radon does not care whether a home is owned or leased, the harm is long-term lung cancer, and the only way to know your level is to test against the 4 pCi/L action level. Tenants should test and communicate; landlords should test, mitigate, and document. Certified professionals handle mitigation, and a physician handles health questions, since radon offers no symptoms to watch for and rewards only those who measure and act.
Radon in multi-unit buildings
Apartment buildings and other multi-unit rentals present radon questions that differ from single-family rentals. Radon enters from the soil, so ground-floor and basement units have the most direct exposure pathway, while upper-floor apartments tend to test lower because they are farther from the source and the gas dilutes as it rises. This vertical gradient means a single test cannot represent an entire building.
For a landlord or property manager assessing a multi-unit building, testing representative ground-contact units is the sensible starting point. If lower units test elevated, the building likely warrants attention even if upper floors read low. Shared mechanical systems and stairwells can also move air, and therefore radon, between units, complicating the simple floor-by-floor expectation.
Mitigation in multi-unit buildings can be more involved than in a single home, sometimes requiring multiple sub-slab suction points or systems tailored to the building’s footprint and construction. Certified radon professionals experienced with larger buildings design these systems. For tenants in a ground-floor or garden-level apartment along the Front Range, requesting a test of their specific unit is reasonable, since their exposure may differ markedly from a neighbor several floors up, because radon concentrates near the soil and dilutes as it rises through a building.
Radon and the real estate side of renting
Radon intersects with rentals at several transactional moments, and awareness of these helps both parties. When a landlord buys a property to rent out, the purchase often includes an inspection during which radon testing can be added. Discovering and addressing radon before tenants move in is far simpler than retrofitting around an occupied unit, so the acquisition stage is an ideal time to test and mitigate.
Lease signing is another point where radon can surface. In jurisdictions with disclosure requirements, landlords may need to inform prospective tenants about known radon levels or the presence of a mitigation system. Even where not legally required, a landlord who has tested and can show low levels or a working mitigation system offers a meaningful reassurance that thoughtful renters appreciate. Transparency here builds trust and reduces the chance of a dispute later.
Turnover between tenants offers a natural window for testing and any needed work, since the unit is empty and accessible. A landlord who incorporates radon testing into the turnover routine treats it like any other maintenance item, keeping the property safe and records current. For tenants, asking at lease signing whether the unit has been tested, and when, is a fair question that signals the renter takes the issue seriously and prompts the landlord to address it.
What a tenant should do step by step
A renter who wants to address radon can follow a clear sequence. First, test the unit using a short-term kit or continuous monitor placed on the lowest occupied level, following the device instructions for placement away from drafts. This establishes whether a concern exists relative to the 4 pCi/L action level.
Second, if the result is at or above the action level, document it and notify the landlord in writing, requesting professional confirmation and, if confirmed, mitigation. Keeping a written record, including the test result and the date of the request, protects the tenant and creates a clear paper trail. The EPA recommends acting at or above 4 pCi/L and considering action between 2 and 4 pCi/L, so a result in either range is worth raising.
Third, if the landlord is unresponsive, the tenant can consult local housing authorities, the state health department, or tenant-rights resources to understand their options under local law. Throughout, the tenant’s most reliable protection is to measure, document, and communicate rather than assume a unit is safe or worry about symptoms that radon does not produce. Because radon’s harm is long-term and silent, the renter who tests and acts is far better protected than one who waits for a warning sign that never arrives. Certified professionals should handle any mitigation, and a physician should address health concerns, keeping the tenant’s role focused on detection and clear communication.
Why landlords gain from addressing radon proactively
Landlords sometimes view radon testing as an optional expense, but a closer look shows it serves their interests as much as their tenants’. A property with documented low radon, or a working mitigation system, is more marketable to the growing number of renters who research health and safety before signing. Transparency about radon can differentiate a unit in a competitive rental market.
There is also a risk-management dimension. As awareness of radon grows and more jurisdictions adopt disclosure or testing rules, a landlord who has already tested and mitigated is ahead of evolving requirements rather than scrambling to comply. Documented good-faith action reduces the chance of disputes and demonstrates responsible stewardship should a tenant ever raise a concern.
Cost favors proactivity too. Testing is inexpensive, and addressing radon during a vacancy or renovation is far simpler than retrofitting around an occupied unit with a frustrated tenant. For Front Range landlords, where elevated radon is common, folding radon testing into routine property management is a modest investment that protects tenants, supports marketability, and positions the owner well as expectations tighten. Treating radon as ordinary property care, like checking smoke detectors, is the sensible posture for any landlord operating in radon-prone Colorado.
References
- Radon testing, the action level, and renter guidance — U.S. Environmental Protection Agency
- Radon in assisted and public housing — U.S. Department of Housing and Urban Development
- Radon in Colorado rental housing — Colorado Department of Public Health and Environment
- Radon health effects — Centers for Disease Control and Prevention
Frequently asked questions
Does radon affect rental housing?
Yes. Radon seeps from soil into any ground-contact building, including apartments, duplexes, and single-family rentals. Lower-floor units over basements or crawl spaces are most likely to have elevated levels, and renters face the same long-term lung-cancer risk as homeowners.
Who is responsible for radon in a rental?
It depends on state and local law. Some states require landlord disclosure or testing; others have no specific duty unless the lease or local rules create one. Because mitigation involves structural systems, it generally falls to the landlord, who owns and controls the property.
Can a tenant test for radon?
Yes. A tenant can use an inexpensive short-term test kit or a continuous monitor in the lowest occupied space. If results reach or exceed the EPA action level of 4 pCi/L, the tenant can bring that documentation to the landlord in writing to request professional confirmation and mitigation.
How is radon fixed in a rental unit?
The standard fix is sub-slab depressurization, a vent pipe and fan that draws radon from beneath the foundation and exhausts it above the roofline. Properly installed systems bring levels below 4 pCi/L, and a follow-up test confirms the result for all occupants.
Front Range tenants and landlords who want a rental tested or mitigated for radon can connect with a vetted local professional through our contact page to get the right testing and a reliable fix.
Test your home for radon
Radon is invisible and odorless, so a test is the only way to know your level. A short-term kit gives a first reading in days; a digital monitor tracks it over time.
| Product | Why | Buy |
|---|---|---|
 AirChek Charcoal Radon Test Kit | Lab fee usually included; EPA short-term protocol. | Amazon — $21.95 |
 First Alert RD1 Radon Test Kit | Widely stocked; 48-hour charcoal test. | Amazon — $16.98 |
 Airthings Corentium Home | Digital monitor with a long-term average. | Amazon — $143.65 |