Radon Levels & Zone Map in Lyman County, SD
Direct Answer for basement and lowest-level tests: Lyman County backs up the EPA high-zone warning. Official county data shows 22.1 pCi/L and 100.0% at or above 4.0. Do the home test, and treat a confirmed 4.0+ result as mitigation-planning territory.
Treat this as a test-now county
The official source signal is strong enough that a first test is the minimum; a confirmed 4.0+ result should move into cost or credit planning.
Official measured data puts this county in a high-priority testing lane.
2.0-3.9 pCi/L usually means retest or track. 4.0+ is where EPA action and quote planning start to matter.
No reading: test now. Reading at 4.0+: move into mitigation planning.
Measured Radon Data
Lyman County evidence before the next step
Lyman County, SD has more than the EPA map: CDC Tracking Network exposes 2 reported tests, 22.1 pCi/L county average, 22.1 pCi/L median, 100.0% of reported tests at or above 4.0 pCi/L, and 31.7 pCi/L high-end signal for 2008-2017.
Source window
2008-2017
County evidence type
High measured burden
County context only; your home test controls the decision.
Primary result
22.1 pCi/L
94th percentile in-state
4.0+ signal
100.0%
100th percentile in-state
High-end signal
31.7 pCi/L
68th percentile in-state
Official evidence dossier
Source record for Lyman County, SD
CDC Tracking provides comparable county-level measurement fields; state-specific sources still outrank it when they expose stable county tables.
Primary public source
National tracking data
Measurement window
2008-2017
Retrieved / checked
2026-05-05
County FIPS
46085
Evidence stack
County source
National tracking data
Primary source used for the county evidence row.
Federal map
EPA Map of Radon Zones
Zone 1 is context, not a property result.
Housing context
US Census ACS housing context
35.6% built before 1980; 1,560 housing units.
State follow-up
State radon program
Use the state source before hiring or interpreting local rules.
Primary field
22.1 pCi/L
Median field
22.1 pCi/L
4.0+ field
100.0%
Sample / volume
2 over 10 years
Metric shape
This is the most useful setup: county average, 4.0+ share, high-end readings, and 2 reported tests/properties can be read together instead of relying on one number.
Source limitation
CDC county summaries are based on national radon testing laboratories and participating state feeds; they are not a statistically designed survey of every home.
Property-level limit
Not a property-level diagnosis. The county record explains local evidence; your home's own test result controls the next decision.
County-specific interpretation
Lyman County crosses the action threshold in the official county data.
Lyman County is a test-now case because 22.1 pCi/L average, 22.1 pCi/L median, and 100.0% of reported tests at or above 4.0. In-state rank: 94th percentile for average, and 100th percentile for 4.0+ share. No reading means get the first number; a 4.0+ home result should move straight to mitigation quotes or seller-credit math.
Real-estate use
Buyer or seller use: ask for a fresh lowest-level test before inspection deadlines, tie any 4.0+ result to a contractor quote, and do not negotiate from the county signal alone.
Lyman County should be treated as a county where a first test is urgent and a 4.0+ result should move directly into mitigation pricing or seller-credit math.
Use This EvidenceOfficial state path
Open the state radon program
Use state rules and local program contacts before choosing a contractor.
EPA hiring guidance
Find a qualified radon provider
EPA points homeowners to state programs and national proficiency listings.
Certified professional search
Search NRPP-certified pros
Use this after you have a valid result or need professional testing.
High-risk intent answer
Is radon bad in Lyman County?
Lyman County should be treated as a high-priority testing market because 100.0% of reported tests at or above 4.0 pCi/L, 22.1 pCi/L primary measured result, and 31.7 pCi/L high-end signal in CDC Tracking Network data. A missing home reading means test now; a 4.0+ result means mitigation pricing or seller-credit math should start.
Enter the result. Pick the deal side. Get the route.
Official measured data puts this county in a high-priority testing lane.
County signal
22.1 pCi/L
At or above 4.0
100.0%
Decision side
Foundation clue
Choose your next step
Start from the exact job, not another generic radon article.
Pick the situation that matches Lyman County, SD. Each route keeps the reading, deal side, or foundation clue attached so the next page answers the search instead of resetting the user.
Failed inspection
I need a repair or seller credit number
Open the local credit path with a 4.0+ buyer scenario already selected.
Open negotiation route4.0+ pCi/L
I have a high result and need the cost path
Go straight to the county estimate, quote context, and contractor checklist.
Open cost route2.0-3.9 pCi/L
I need to know if this number is bad
Use the level explanation first, then decide whether to retest, monitor, or price mitigation.
Open level routeNo test yet
I need the first valid result
Start with kit placement, timing, closed-house conditions, and result interpretation.
Open testing routePick the situation that matches you
You should not need to read the whole guide before clicking one of these. Start with the lane that matches your current stage, then come back for the deeper reference only if you still need it.
Jump into a prefilled Lyman County action plan based on the result you already have, instead of starting from a generic cost page.
I have not tested yet
Do not price mitigation blind. Get the first number, then decide whether you need monitoring, quotes, or nothing at all.
My result is 2.0-3.9
Usually confirm the reading first. If it keeps showing up, use the county evidence and official guidance before deciding whether pricing makes sense.
My result is 4.0+
This is the EPA action line. Use the local cost page before calling contractors so you know the likely scope, timing, and budget.
I am buying or selling
Turn the reading into a credit or repair number before negotiation starts. This is the faster path than arguing from a generic article.
Already tested once and need the cleanest follow-up path?
Review retesting stepsCounty Evidence Snapshot
Lyman County testing context
Lyman County should be treated as a testing-priority county because the official source signal backs up the EPA high-zone warning. Official county data shows 22.1 pCi/L and 100.0% at or above 4.0. Use the EPA map as context, but let the home test decide mitigation or credit planning.
EPA map signal
Zone 1
County-level predicted indoor screening range, not a home-level test result.
Housing base
1,560
34th percentile among 65 SD counties with data.
Older housing share
35.6%
55th percentile in-state; older homes often need clearer test placement decisions.
Median home value
$132,100
Used as context for whether mitigation is a small maintenance item or a negotiation issue.
Measured Radon Data
CDC Environmental Public Health Tracking Network Radon Tests from Labs
2008-2017
Average result
22.1 pCi/L
At or above 4.0
100.0%
Maximum reported
31.7 pCi/L
10-year tested
2
CDC county summaries are based on national radon testing laboratories and participating state feeds; they are not a statistically designed survey of every home.
County evidence interpretation
High measured burden
Primary result rank
94th percentile
22.1 pCi/L
4.0+ rank
100th percentile
100.0% at or above 4.0
High-end rank
68th percentile
31.7 pCi/L
Test volume rank
18th percentile
2 over 10 years
How to use this county data
Data source
National tracking data
CDC Tracking provides comparable county-level measurement fields; state-specific sources still outrank it when they expose stable county tables.
What the numbers show
Fuller county picture
This is the most useful setup: county average, 4.0+ share, high-end readings, and 2 reported tests/properties can be read together instead of relying on one number.
Nearby comparison
Nearby comparison: Closest counties by share of tests at or above 4.0 pCi/L: Harding County (100.0%) is just lower, and Sully County (100.0%) is just higher.
How this helps
Use this to decide how urgently to test, retest, or plan mitigation after a 4.0+ result.
What the data says
Lyman County, SD is measurement-backed for 2008-2017. The measured average is 22.1 pCi/L, and 100.0% of reported results are at or above 4.0 pCi/L. The high-end signal reaches 31.7 pCi/L.
Lyman County, SD sits at the 94th percentile for measured average, 100th percentile for 4.0+ share, 68th percentile for high-end readings, and 18th percentile for test volume among 66 measured counties in the state. Closest counties by county average: Jones County (20.5 pCi/L) is just lower, and Lawrence County (29.0 pCi/L) is just higher.
What to do with it
Lyman County should be treated as a county where a first test is urgent and a 4.0+ result should move directly into mitigation pricing or seller-credit math.
Retest trigger: a 2.0-3.9 pCi/L home result should be confirmed here because 22.1 pCi/L average, 22.1 pCi/L median, and 100.0% of reported tests at or above 4.0 keeps the county from being a dismiss-it signal.
Source-backed context from CDC Tracking Network based on about 2 reported tests/properties plus comparable county-level measurement fields.
No reading yet
No reading yet: run a short-term test now, then confirm or price mitigation quickly if the result is elevated.
2.0-3.9 result
2.0-3.9 pCi/L: retest or track longer-term rather than dismissing the result, because the county distribution has meaningful elevated readings.
4.0+ result
4.0+ pCi/L: use the result for mitigation quotes, repair scope, or seller-credit negotiation; the county signal is no longer the deciding input.
Source hierarchy: CDC Tracking Network is used for this county, with EPA zone and Census housing data kept as supporting context. CDC Tracking provides comparable county-level measurement fields; state-specific sources still outrank it when they expose stable county tables.
Direct Answer
Is radon bad in Lyman County?
Lyman County should be treated as a high-priority testing market because 100.0% of reported tests at or above 4.0 pCi/L, 22.1 pCi/L primary measured result, and 31.7 pCi/L high-end signal in CDC Tracking Network data. A missing home reading means test now; a 4.0+ result means mitigation pricing or seller-credit math should start.
| Evidence | Value |
|---|---|
| Area | Lyman County, SD |
| EPA Zone | Zone 1 |
| Primary Recommendation | Perform direct radon testing in the lowest livable level |
Your Radon Reading
Enter your home's measured level; the starting value is only a planning example until you have your own result.
Warning: Action Required - EPA Threshold Exceeded
At 5.5 pCi/L, this reading is above the EPA action level. Prompt mitigation planning is recommended after confirmatory testing.
Typical mitigation systems reduce radon by 80-99%. See your itemized cost estimate below.
Understanding Radon Levels: Complete Reference
Below 2.0 pCi/L - Lower Concern, Keep Testing
Below both the EPA (4.0) and WHO (2.7) action reference levels. This usually means mitigation is not the next immediate step after a confirmed result. The average outdoor radon level is approximately 0.4 pCi/L, and there is no known risk-free indoor level. Periodic testing is still recommended because levels can change over time due to seasonal variations, changes in home ventilation, or foundation settling.
-4.0
2.0 - 4.0 pCi/L - Elevated, Consider Action
Exceeds the World Health Organization's reference level of 2.7 pCi/L but falls below the US EPA action threshold. The EPA states that homeowners should "consider fixing" homes in this range, especially if the home has a basement used as living space, if children are present, or in connection with a real estate transaction. Practical next step: run a confirmatory long-term test, then compare mitigation quotes if levels remain elevated.
-8.0
4.0 - 8.0 pCi/L - Action Recommended
Exceeds the EPA action level of 4.0 pCi/L. The EPA and Surgeon General strongly recommend mitigation within a few months. At this level, prioritize confirmatory testing and contractor planning. Standard sub-slab depressurization systems typically reduce indoor levels by 80-99%.
Above 8.0 pCi/L - Urgent Action Required
At these levels, the EPA recommends expedited mitigation - ideally within weeks, not months. Occupants should minimize time in lower-level rooms until the system is installed. Use a certified mitigator and request priority scheduling to shorten high-exposure time. Many mitigators offer priority scheduling for homes above 8.0 pCi/L.
Why Radon is a Testing Priority in Lyman County
The EPA map is only the starting layer for Lyman County. Official county data shows 22.1 pCi/L and 100.0% at or above 4.0. That source-backed signal is why the practical move is testing or retesting before treating the county as low urgency.
This still is not a diagnosis for any single home. Foundation type, lowest-level use, pressure differences, and small geological changes can move one house above or below the county pattern.
If you do not have a reading yet, start with a short-term test in the lowest lived-in level. If the result is 2.0-3.9 pCi/L, confirm it; if it is 4.0+ pCi/L, move into mitigation pricing or seller-credit planning.
Radon & Health: What the Science Says
lung cancer
from radon
4.0 pCi/L
Radon is a Class A carcinogen - the same classification as asbestos and tobacco smoke. The National Academy of Sciences estimates that radon causes approximately 21,000 lung cancer deaths annually in the United States, making it the leading environmental cause of cancer death.
Unlike smoking, radon exposure is involuntary and often invisible. There is no safe level of radon - risk increases linearly with exposure. The good news: radon mitigation systems are highly effective, typically reducing indoor levels by 80-99% within hours of activation.
Source: US Environmental Protection Agency, "A Citizen's Guide to Radon" (EPA 402/K-12/002). National Academy of Sciences, Biological Effects of Ionizing Radiation (BEIR VI) Report, 1999.
Step 1: Test Your Home
Testing is the only way to know your home's radon level. Zone and county data tell you the regional signal, but your home could be significantly higher or lower than the countywide pattern. Start with a valid test setup before using any cost path.
State radon programs and EPA provider guidance are the right reference before hiring or confirming local requirements.
Open the state radon programAlready Know Your Level?
If your test shows 4.0 pCi/L or higher, get an itemized cost estimate specific to Lyman County - including regional labor rates and permit requirements.
Get Mitigation Cost Estimate ->SD Radon Regulations
South Dakota requires sellers to disclose known property conditions through a Property Condition Disclosure Statement.
South Dakota does not require specific radon licensing.
How to Test for Radon in Lyman County
Buy a Test Kit
Purchase a short-term charcoal test kit online or from a local hardware store. Cost: $15-$30. Place it in the lowest livable level of your home.
Wait 2-7 Days
Keep doors and windows closed (except normal entry/exit) during the test period. Avoid running whole-house fans. Mail the kit to the lab provided.
Read Your Results
If results are below 4.0 pCi/L, re-test every 2 years or use a monitor for ongoing tracking. If above 4.0, use our cost calculator to see mitigation options.
Related Radon Resources for Lyman County
Explore Other SD Counties
Official State Resource
South Dakota radon program and rules
Use the state program link to verify local radon guidance, disclosure language, and contractor credential expectations before you act on an estimate.
Disclosure rule tracked
South Dakota requires sellers to disclose known property conditions through a Property Condition Disclosure Statement.
Credential note
South Dakota does not require specific radon licensing.
Sources & Methodology
Radon zone classifications for Lyman County are sourced from the EPA's Map of Radon Zones, which uses geological surveys, indoor radon measurements, and soil permeability data to assign each county a risk tier.
Disclaimer: Zone data represents county-level screening ranges and cannot predict the radon level in any specific home. Testing is the only reliable method to determine your home's radon concentration. This content is for informational purposes and is not medical advice.
Content review: Source-level retrieval dates
Editorial and Data Transparency
- Author
- RadonVerdict Data Team (Public Data and Cost Modeling)
- Content Review
- Source-level dates shown below
- Data Retrieved At
- 2026-02-24
Primary Sources
- EPA Map of Radon Zones (retrieved 2026-02-21)
- EPA A Citizen's Guide to Radon (retrieved 2026-05-05)
- CDC Environmental Public Health Tracking - Radon Testing (retrieved 2026-05-05)
- Official SD radon program
- US Census Bureau, 2018-2022 American Community Survey 5-Year Estimates (retrieved 2026-02-24)