More than one in four radon tests in Plymouth comes back at or above the EPA's 4.0 pCi/L action level. Of 4,918 tests on the state record from 2015 to 2024, 1,295 hit that line. The highest was 182.9.
Plymouth is the most heavily tested town in this service area and it carries the highest share of elevated results. Here is what the record shows, and what it means for your address.
Massachusetts DPH publishes every radon test result reported in the state by town. Here is what 4,918 Plymouth tests from 2015 through 2024 look like.
| Measure | Plymouth, MA | What it means |
|---|---|---|
| Tests on record, 2015-2024 | 4,918 | The sample this table is built on |
| Median result | 2.3 pCi/L | Half of Plymouth homes tested came in below this |
| Geometric mean | 2.3 pCi/L | The typical result, with outliers damped |
| Tests at or above 4.0 pCi/L | 1,295 (26.3%) | EPA says fix the house at this level |
| Tests between 2.0 and 4.0 | 31.2% | EPA says consider fixing |
| Tests below 2.0 | 42.5% | No action recommended |
| Highest single result on record | 182.9 pCi/L | One house, not the town, but it was somebody's house |
| Tests per 1,000 occupied homes | 196.8 | How thoroughly the town has actually been checked |
Source: Massachusetts Department of Public Health radon testing data, town-level export, 2015-2024.
Plymouth is large enough that the foundation under your house matters more than the town average. Fieldstone antiques in Chiltonville leak soil gas through every mortar joint, and they need sealing work before a fan does any good. Postwar ranches in North Plymouth and West Plymouth sit on poured slabs where a single well-placed suction point usually carries the whole floor.
Coastal capes in Manomet and Cedarville often grew a crawlspace addition at some point, and a crawlspace needs a sealed membrane rather than a slab penetration. Slab-on-grade homes in The Pinehills put living space directly on the soil with no basement buffer at all, which is why newer construction here is not automatically low.
That 182.9 reading was one house. It was somebody's house. The town median of 2.3 pCi/L would never have predicted it, which is the whole argument for testing the address instead of reading the average.
The EPA Map of Radon Zones assigns Plymouth County to Zone 2, which predicts an average indoor screening level between 2.0 and 4.0 pCi/L. Barnstable, Bristol and Norfolk counties carry the same designation. Worcester, Middlesex and Essex are Zone 1.
The EPA prints a warning on the same map: it should not be used to decide whether an individual home gets tested, and all homes should be tested regardless of zone. The Plymouth numbers in the table above show why. A county-wide prediction cannot tell you what is under one address.
Massachusetts does not license radon contractors. The state's own guidance points homeowners at professionals certified by NRPP or NRSB, and those two certifications are the only credential worth asking about. Ask for the number, not the logo.
An active system puts a fan in the vent stack, and wiring that fan is electrical work, so the Plymouth wiring inspector is normally the one permit stop on a mitigation job. We pull it. Systems that vent above the roofline and discharge away from windows meet the EPA protocol the inspector is checking against.
State testing data says yes for a meaningful share of houses. Of 4,918 Plymouth tests on record from 2015 through 2024, 26.3% came back at or above the EPA's 4.0 pCi/L action level, and another 31.2% landed between 2.0 and 4.0. The town median is 2.3 pCi/L.
Most single-family systems in this county run $1,200 to $2,500 installed, with a post-mitigation retest included. The price turns on foundation type and how many suction points the slab needs, which is why we quote in writing after seeing the house.
A short-term test needs a minimum of 48 hours under closed-house conditions. We use continuous monitors that log hourly, so a test placed Monday is reported Wednesday. Real estate deadlines get priority placement.
Nothing in Massachusetts law requires one, but radon testing is standard practice in home-sale inspections here, and buyers routinely ask for mitigation or a credit when a result comes back high. Testing inside the inspection window costs less than renegotiating after you own it.
State data is published by town, not by neighborhood, so nobody can honestly rank them. What the foundation type predicts is more useful: fieldstone cellars in Chiltonville, slab-on-grade in The Pinehills, and crawlspace additions in Manomet and Cedarville each fail differently. We test the lowest lived-in level either way.
One call covers testing, mitigation, well-water treatment and system repair anywhere in Plymouth and the rest of Plymouth County. Written quote first, retest after.
Sources: Massachusetts Department of Public Health radon testing data 2015-2024; EPA Map of Radon Zones, Massachusetts.
Radon Mitigation for Plymouth and Plymouth County. Test it. Fix it. Prove it's fixed.
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