When to test, and why the month matters
Radon levels rise in winter. A heated house pulls harder on the soil beneath it, the windows stay shut, and the gas that would otherwise disperse accumulates. The York County record shows exactly how large that effect is.
February runs at 13.19 pCi/L and July at 6.87, a difference of 92 percent between the extremes. That is not a small seasonal wobble. It is the difference between a house that looks fine and the same house looking like a problem.
The practical consequence is uncomfortable for anyone testing in summer. A July reading of 3.5 pCi/L looks safely under the action level, and the same house in January could sit above it. If you test in warm weather and land anywhere near 4, treat the result as provisional and retest in the heating season before deciding you have nothing to fix.
Which test method to ask for
Five methods appear in the York County record, and they are not interchangeable. The differences are mostly about how long the device sits in the house rather than how accurate it is.
| Method | Tests on record | Average result |
|---|---|---|
| Charcoal canister, short term | 43,499 | 10.72 |
| Continuous monitor | 22,326 | 9.94 |
| Liquid scintillation | 18,113 | 12.92 |
| Electret, short term | 12,895 | 9.70 |
| Alpha track, long term | 1,961 | 7.94 |
Read those averages with care, because they compare different situations rather than different accuracies. Short term devices tend to be deployed in winter and during property sales, when readings run high. The alpha track detector sits in the house for months and averages across seasons, which is why it comes out lowest and also why it gives the most representative picture of what you actually breathe.
For a first test, a charcoal canister is the cheapest route and it is what most York County households used. For a decision with money attached, a continuous monitor placed by a certified tester gives an hour by hour record that cannot be accidentally disturbed. For knowing what your family is really exposed to over a year, the long term alpha track is the honest instrument.
Where the device goes, and what the number means
Nearly all testing happens in the basement, and that choice shapes every number you will read about radon. Of the York County tests recording a floor level, 81,840 were basement readings.
| Where tested | Tests | Average | At or above 4 |
|---|---|---|---|
| Basement | 81,840 | 11.79 | 56.5% |
| First floor | 10,682 | 5.84 | 33.5% |
| Second floor | 1,086 | 5.43 | 29.4% |
| Slab on grade | 2,109 | 6.35 | 37.2% |
A basement reads roughly twice a first floor. That is not a reason to test upstairs instead. The guidance is to test the lowest level you use or could reasonably finish, because a basement you turn into an office next year becomes the room where exposure happens.
It is a reason to interpret your number correctly. A basement result of 9 pCi/L does not mean your upstairs bedroom sits at 9. It means the entry point is strong, the lowest level needs fixing, and your living space is probably somewhere around half that figure. Both facts point the same way, but only one of them is what you breathe.
Getting a result you can rely on
- Closed house conditions. Windows and outside doors shut for twelve hours before the test and throughout it. Short term tests measure the worst realistic case, and opening a window turns the result into fiction.
- Lowest level you use. On a table or shelf, roughly at breathing height, away from drafts, exterior walls, sump pits and heat.
- Leave it the full period. Two to seven days for a short term device, ninety days or more for a long term one. Cutting it short invalidates the reading.
- Send it in promptly. Charcoal keeps absorbing after you seal it, so a canister that sits in a drawer for a week returns a number that means nothing.
- Retest after any big change. A new heating system, finished basement, replaced windows or major foundation work all alter how the house pulls on the soil beneath it.
If the result comes back at or above 4 pCi/L, the next questions are what a system does and what it costs, which are covered on the pages about how a radon mitigation system works and what mitigation costs in York County.
Testing yourself or hiring a tester
A do it yourself kit is perfectly legitimate for finding out whether you have a problem. Pennsylvania requires DEP certification to test professionally, but nothing stops a homeowner buying a kit and posting it to a lab.
Certification matters when the result has consequences for someone else. What a result means at the closing table is covered on the page about buying or selling a house with radon. A test used in a property sale should come from a certified tester, because the buyer is entitled to a result the seller could not have influenced, and because a device left unattended in a house being sold is a device somebody has an incentive to move. The York County contractor list marks which firms test and which also mitigate.
Common questions about radon testing
What time of year is worse for radon?
Winter. Across York County results, December to February averages 12.90 pCi/L against 7.17 for June to August, an 80 percent difference. February is the highest month at 13.19 and July the lowest at 6.87.
Can a summer radon test be trusted?
For a clearly high or clearly low result, yes. For anything near 4 pCi/L, a summer reading understates the winter figure, so retest in the heating season before concluding the house is fine.
How long does a radon test take?
A short term test runs two to seven days with the house closed up. A long term alpha track detector stays in place for ninety days or more and gives a better picture of year round exposure.
Should I test the basement or the living area?
Test the lowest level you use or might finish. Basements average 11.79 pCi/L in York County against 5.84 on the first floor, so a basement number is not what you breathe upstairs, but it is where mitigation is decided.
How much does a radon test cost?
A charcoal canister kit is the cheapest route and the most used method in the county record. A professional test by a DEP certified tester costs more and is the right choice when a property sale depends on the result.
Do I need a certified tester?
Not for your own information. Pennsylvania requires DEP certification for professional testing, and a certified tester is the right choice when the result will be used in a sale, because the buyer needs a reading the seller could not influence.