RadonGuys / Chapin Environmental

RadonGuys, formerly Chapin Environmental, has been mitigating radon in Massachusetts homes since 1989 — founded by brothers John and Scott Chapin, and owned by James Duffy since 2017. The Millis-based company's own site says it does not test for radon at all, sending customers to a third-party lab specifically to avoid a conflict of interest with its mitigation work. Across 25 written Google and HomeAdvisor reviews running from 2019 through 2025, every single one is five stars, and the same specifics keep showing up: homeowners cite exact before-and-after radon readings — one dropped from just under 12 pCi/L to 0.02, another from around 10 down to under 1.5. One reviewer noted RadonGuys guarantees mitigation to under 2 pCi/L, tighter than a competitor's 4 pCi/L promise. Reviewers name the crew directly — Jim (Duffy), John, and Derek — and describe methodical work; a 2022 review described a technician measuring pressure drop at multiple test points to verify the system was actually working, in a basement complicated by sand and extensive cracking under the slab. Nothing negative shows up anywhere in this record. The one thing worth confirming directly before booking: since RadonGuys does not test for radon itself, a homeowner without an existing reading should expect to be pointed to a separate lab first. This is the right call for someone who already knows they have elevated radon and wants a specialized, guarantee-backed mitigation install rather than a general inspector — confirm the guaranteed pCi/L threshold and price up front.