Radon Gas Check: What Homeowners Need to Know
“Radon gas check” is the casual shorthand homeowners use when they have not yet learned the formal language of radon measurement. It captures the right intent — find out whether radon is present in the home — and the methods behind the casual phrase are the same as those used by certified inspectors. The difference is accessibility. A radon gas check costs $15 at a hardware store, takes 48 hours, and answers the basic question. This guide walks through how to do a radon gas check for the first-time tester: where to buy a kit, how to set it up, how to read the result, and what to do next. EPA and CDPHE guidance current as of 2026 — consult a physician for symptoms and a certified professional for mitigation decisions.
Radon Gas Check: The Basic Idea
A radon gas check measures the concentration of radon gas in indoor air over a defined time window. The result reports as picocuries per liter (pCi/L). The EPA action threshold is 4.0 pCi/L; below that, no immediate action is recommended; at or above that, mitigation is recommended.
The check itself does not require expertise. A homeowner can buy a kit at Home Depot or Lowe’s, place it correctly in the basement or first floor, leave it alone for 48 hours, and mail it to the lab. The lab does the actual measurement. The homeowner gets an emailed result within a week of mailing. Total cost is $15 to $40 depending on kit type and lab fees. Total elapsed time from purchase to result is 7 to 14 days.
Three things differentiate a “gas check” from a more formal radon inspection: the documentation, the device class, and the chain of custody. A real-estate transaction needs all three. A homeowner curious about their own house needs none of them. The result of an accurate consumer radon test is just as physically real as a certified-inspector test result.
Where to Buy a Kit
Three retail paths exist. Big-box hardware stores (Home Depot, Lowe’s, Ace) stock charcoal-canister short-term kits from Air Chek, Pro-Lab, and Accustar for $15 to $25 each. The kit includes one canister, one chain-of-custody card, and prepaid return shipping to the lab. Amazon stocks the same kits at similar pricing with two-day shipping.
Direct-from-lab ordering is the second path. Labs like Accustar Labs, Air Chek, and Radon FTW ship kits direct with $10 to $20 per-test pricing for bulk multi-test packs. State health departments also offer reduced-price or free kits to residents in some states. The Colorado Department of Public Health and Environment offers low-cost kits through county extension offices in some Front Range counties; eligibility varies by year and county budget.
The third path is a consumer continuous radon monitor (CRM). Airthings Wave Plus ($230), Airthings View Plus ($300), and Ecosense RadonEye ($150) provide continuous monitoring rather than a single-shot check. CRMs are more expensive upfront but provide ongoing data after the initial purchase. The how kits work guide covers consumer CRM specifics.
Setting Up the Check
Placement rules apply equally to short-term canisters, alpha-track detectors, and consumer CRMs. The fundamentals: lowest livable level of the home, 20 inches to 6 feet above the floor, 4 inches minimum from interior walls, 3 feet from exterior doors and windows, 1 foot from heating/cooling sources or strong air currents, away from kitchens and bathrooms with high humidity.
Pre-test conditions matter. Close all exterior doors and windows for at least 12 hours before starting the test. Operate the HVAC normally during the test. Do not run whole-house fans, attic fans, or window AC units. Avoid testing during severe weather that disrupts normal house pressure.
Note the start time on the chain-of-custody card or in the consumer CRM app. Leave the device alone for the full test duration. The standard short-term test is 48 hours minimum, 96 hours preferred. EPA recommends not exceeding 7 days for short-term testing because activated charcoal begins to lose absorbed radon back to the air after extended exposure.
Mailing the Sample
For charcoal-canister kits, the post-test workflow is time-sensitive. At the end of the test window, seal the canister immediately per kit instructions — usually a foil seal or a screw-cap lid included in the kit. Complete the chain-of-custody card with start time, end time, location, and contact info. Place the canister and card into the prepaid envelope and mail it the same day or the next morning.
The reason for time sensitivity: charcoal-absorbed radon decays continuously with a 3.8-day half-life. The lab corrects for decay between test end and lab receipt, but corrections are more accurate when transit time is short. A canister sitting in a homeowner’s bag for two weeks before mailing produces a result with larger uncertainty bands than one mailed immediately.
Lab turnaround is typically 3 to 7 business days from receipt. Most labs email the result to the address on the chain-of-custody card. Some labs post results to an online portal as well.
Reading the Result
The lab report shows a single number in pCi/L. Some reports also include the test duration and the date range. The interpretation is direct against EPA thresholds.
Below 2.0 pCi/L is considered acceptable by EPA, with no immediate action recommended. EPA suggests re-testing every 2 years to confirm conditions remain stable. Between 2.0 and 3.9 pCi/L is in the “consider mitigation” range — risk is elevated but the action level is not crossed. Some homeowners choose to mitigate at this level; others retest with a longer-duration alpha-track detector to confirm the average.
At or above 4.0 pCi/L, EPA recommends mitigation. A first high result warrants a confirmation test — either a second short-term in the same location or a long-term alpha-track. If both confirm elevated levels, the next step is to consult an AARST/NRPP-certified mitigation contractor. The radon testing pillar covers Front Range-specific context for high-result decisions.
Common Mistakes During a Radon Gas Check
Several routine errors invalidate results or skew them low. Opening windows during a short-term closed-house test is the most common. The resulting reading will be artificially low because outdoor air dilutes the indoor radon concentration. Re-running the test with proper closed-house conditions usually shows higher levels.
Placing the kit too close to an exterior wall, an HVAC supply register, or a window also distorts the reading. The kit needs to sit in still-air conditions to absorb a representative sample. Testing during high winds, rapid barometric pressure changes, or unusually warm winter weather can produce results outside typical ranges. EPA recommends repeating any test that occurs during severe weather.
Another error is testing on an upper floor when the basement is the highest-risk location. EPA protocol places the device in the lowest livable level. A test on the third floor of a four-level home will underestimate basement-level exposure.
When to Repeat the Check
EPA recommends re-testing every 2 years even if the initial result was below 2.0 pCi/L. Re-test annually if the initial result was between 2.0 and 3.9 pCi/L. Re-test after major foundation work, HVAC replacement, or window/door changes that could alter radon entry paths. Re-test immediately after any mitigation system installation to confirm the system is working.
Seasonal variation is real, especially in Colorado. Winter levels can be 50 percent higher than summer levels because closed houses and active heating create stronger sub-slab pressure differentials. A summer test that comes back at 3.5 pCi/L might exceed 4.5 pCi/L in winter. Long-term alpha-track detectors are the best tool to capture annual averages and avoid being fooled by seasonal lows.
First-Time Tester Step-by-Step
The first-time radon test is procedurally simpler than the surrounding discussion sometimes suggests, and the practical workflow takes about 30 minutes of active time spread across several days. Step one is purchasing the kit. The EPA citizen’s guide to radon directs consumers to kits that are listed on the National Radon Proficiency Program or National Radon Safety Board approved-device lists. Standard kits run $15 to $30 at home-improvement retailers or through online sellers, with the price usually including the postage-paid return mailer and the lab analysis. Reading the kit instructions completely before opening anything prevents most common procedural errors.
Step two is registering the barcode online. Almost every modern kit requires online registration before the test starts. The registration page captures the homeowner’s name, mailing address, email for the report, and the kit serial number printed on the device. Skipping registration is the most common reason result delivery stalls after the test is mailed, because the lab has no way to route the certificate to the homeowner without the registration data.
Step three is following the placement instructions. The device goes in the lowest occupied level of the home, on a flat surface 28 to 60 inches above the floor, at least 20 inches from walls and ceilings, at least three feet from windows, exterior doors, and HVAC supply registers. The closed-house condition begins 12 hours before the test starts; windows and exterior doors remain closed except for normal entry and exit; HVAC operates normally; whole-house fans and attic fans stay off. The kit instructions specify the exposure window, typically two to seven days for short-term tests.
Step four is the wait. Nothing about the test requires daily attention. The household goes about normal activities while the device collects the measurement. Step five is mailing the device. At the end of the exposure window, the homeowner removes the device, seals it according to the kit instructions, fills in the chain-of-custody fields (start date, end date, room location), and places the package in the postage-paid return mailer. Mailing the same day the exposure window ends is important because charcoal canisters continue to release adsorbed radon during transit, and a longer transit time reduces the accuracy of the back-calculation. Step six is receiving the result. The lab typically issues a PDF certificate within five to ten business days of receipt, depending on the lab and service tier selected.
Interpreting Common Results
Result interpretation is the step that gives most first-time testers pause, and the framework is simpler than the underlying physics. A result below 2.0 pCi/L is generally treated as good. The level is below the EPA action threshold, below the half-action consideration zone, and consistent with typical indoor air in most U.S. homes. Re-testing every two years is the standard recommendation in this range, plus any time major renovations alter foundation penetrations or HVAC configuration.
A result between 2.0 and 4.0 pCi/L is the consider-mitigation zone. EPA guidance does not require action at this level but does suggest that mitigation is worth considering, particularly for households with long-term occupancy plans, children, or smokers (because radon and tobacco interact multiplicatively on lung cancer risk). Many homeowners in this range choose to install mitigation as a precautionary measure, and the cost-benefit math is reasonable: mitigation systems run $800 to $2,500 per CDPHE radon information and provide long-term risk reduction.
A result between 4.0 and 10 pCi/L is the strongly-recommended-mitigation zone. EPA action level guidance applies here, and mitigation is the expected response rather than the optional one. Time to act is generally measured in months rather than weeks, and homeowners can schedule mitigation around their convenience as long as the work happens reasonably promptly. A result above 10 pCi/L is the urgent-action zone. Concentrations at this level represent meaningful long-term exposure risk, and homeowners are advised to schedule mitigation as soon as practical, generally within 30 to 60 days. Households with vulnerable members (children, elderly residents, immunocompromised occupants) should treat the timeline more aggressively. Confirmation testing with a different device or laboratory is reasonable before any major decision in the high-result range, because lab errors do occur and a second measurement establishes that the original result was not an outlier.
References
- EPA Citizen’s Guide to Radon — U.S. Environmental Protection Agency
- CDPHE Radon Resource — Colorado Department of Public Health and Environment
- CDC Radon Topic Page — Centers for Disease Control and Prevention
- American Lung Association Radon Information — American Lung Association
Front Range homeowners ready to confirm a high result or coordinate mitigation can connect with a vetted NRPP-certified tester here.