Editorial standards

We would rather say less and be right. Every guide and tool on Radon by ZIP follows these rules.

Sources we use

We rely on the U.S. Environmental Protection Agency (radon zone map, Citizen’s Guide, Home Buyer’s and Seller’s Guide, Consumer’s Guide to Radon Reduction, FAQs), the Centers for Disease Control and Prevention, the World Health Organization, the U.S. Census Bureau, and state radon programs listed by EPA.

We cite the primary source whenever one exists: the statute, the agency page, the court rule, or the extension publication. News articles and industry groups are used only for context and are labeled as such. Each guide lists its sources at the bottom with links.

What we will not do

• We do not invent statistics, testimonials, reviews, expert quotes, or credentials.
• We do not present estimates as measurements. Where a number is a rule of thumb or a model, the page says so and explains the math.
• We do not accept payment to include, rank, or recommend anything in our guides.
• We never ask readers to click ads, and ads are always labeled “Advertisement.”

Tools and data

The ZIP lookup uses EPA’s county zone data and the Census Bureau’s 2020 ZCTA-to-county relationship file, both public. Inferred zones (for counties not listed on the 1993 map) are labeled. The level calculator uses the conversion 1 pCi/L = 37 Bq/m³ and EPA’s published action levels.

Review and updates

Each guide shows the date it was last reviewed. We re-check sources when we learn a rule has changed and at least once a year. When a change matters to readers, we note it on the page.

Corrections

If you find a mistake, use the contact form and include the page and a source. Confirmed errors are fixed promptly, and substantive corrections are noted on the page with the date.

Limits

EPA’s radon zones describe the predicted average for a whole county. Homes next door to each other can have very different radon levels, and EPA says the map should not be used to decide whether a single home needs testing. The only way to know your level is to test. This site is general information, not medical or engineering advice.

This site is operated by Directory Assistance Group. Questions about these terms or your data: hello@directoryassistancegroup.com.