Reviewed and updated September 13, 2026. This article provides general public-health and referral guidance, not testing, medical, legal or engineering advice.
A result below 4 pCi/L is not the same as zero risk
Homeowners often treat 4 pCi/L like a pass-fail line: 3.9 feels safe and 4.1 feels dangerous. Public-health guidance is more nuanced. EPA recommends fixing a home at 4 pCi/L or higher and also recommends considering radon reduction when the level is between 2 and 4 pCi/L because there is no known completely risk-free level of radon exposure.
New York State guidance uses 4 pCi/L as the action level for a confirmed result. If an Elmira, Horseheads or Corning home averages 2.5, 3.2 or 3.8 pCi/L, that does not create the same urgency as a much higher result, but it is reasonable to ask whether additional testing or mitigation fits the household's goals.
First decide whether the number represents the home well
A single short test can be useful, especially when a decision deadline exists, but radon varies over time. Check the test duration, device location and conditions. A basement office used every day matters differently from a utility-only lower level that nobody occupies. A continuous monitor's long-term average also deserves more weight than one isolated hour.
If the result sits close to a decision threshold and there is no urgent transaction, a longer measurement can provide additional context. Do not manipulate ventilation to force the number down. The goal is to understand the normal indoor exposure, not to produce a favorable screenshot.
Household use can influence how you think about mitigation
Two homes with the same 3.5 pCi/L result can create different practical questions. One household may spend little time on the lowest level. Another may have a basement bedroom, playroom or full-time home office. Exposure decisions should be based on credible testing and public-health guidance, while personal medical questions belong with a health professional.
Future use matters too. EPA recommends retesting when living patterns change and a lower level becomes occupied. If a basement in Elmira, Horseheads or Corning is about to become regular living space, that is a sensible time to confirm the radon level and decide whether to reduce it.
Mitigation is a building decision, not a number-only purchase
If you decide to reduce a level between 2 and 4 pCi/L, the system should still be designed for the actual foundation. A contractor should evaluate slabs, crawlspaces, additions, drainage and possible suction routes rather than selling a standard fan based only on the test result.
Cost can vary because the scope varies. Use the Twin Tiers mitigation cost guide to understand the major factors, and ask what post-mitigation testing will be used to verify the work.
Make the decision from the average, the use of the space and your tolerance for exposure
There is no requirement to panic over a 2-to-4 result, but there is also no scientific basis for calling every number under 4 'safe.' The most defensible approach is to confirm the measurement when needed, understand how the home is used and then decide whether further reduction is worthwhile.
If your result is at or above 4 pCi/L, use the high-result guide. If it is between 2 and 4 and you want a property-specific opinion, request an evaluation instead of relying on a generic internet rule.
Sources
Primary guidance used for this article
We use government and public-health sources, distinguish historical datasets from current household measurements, and do not invent local results. Read our editorial policy.