Need a radon reading? DIY charcoal kit steps vs hiring a certified tester

Own the home and can keep closed-house conditions? Short-term kit first. Buying/selling or need a report that stands up? Hire a state-listed / NRPP or NRSB tester — use this index, not a phone lead-gen form.

Radon is a colorless, odorless radioactive gas that can collect indoors. Testing is the only way to know the level in a specific building. This page summarizes U.S. EPA guidance. It is not medical advice.

EPA action level: EPA recommends fixing a home if the radon level is 4 picocuries per liter (pCi/L) or more. EPA also says there is no known safe level of exposure and that Americans may consider fixing levels between 2 pCi/L and 4 pCi/L. The U.S. average indoor level is about 1.3 pCi/L; outdoor air is about 0.4 pCi/L.

Source: What is EPA’s Action Level for Radon and What Does it Mean?

Three common ways to measure

1. Short-term charcoal kit (do-it-yourself)

A charcoal canister or charcoal liquid-scintillation vial sits in the lowest lived-in level of the home, typically for 2 to 7 days (short-term tests run 2–90 days depending on the device). You mail it to a lab. Follow the kit instructions: closed-house conditions, away from drafts, kitchens, and bathrooms.

When a kit is enough

You own the home and want a first look.
You can keep windows and exterior doors closed (except normal entry/exit) for the test period.
You will do a follow-up test if the first result is 4 pCi/L or higher, as EPA recommends, before deciding to mitigate.
Real-estate timing is not tight.

A single short-term result is a snapshot. Radon varies day to day and season to season. EPA’s citizen guidance is: take a short-term test; if it is 4 pCi/L or higher, follow up with either a long-term test or a second short-term test; then decide based on the follow-up (or the average of two short-term tests).

Kits are sold by state radon programs, the American Lung Association, hardware stores, and the National Radon Program Services at Kansas State University. See EPA: Find a Radon Test Kit or Measurement and Mitigation Professional.

Iowa’s radon hotline (1-800-383-5992) and Ohio local health departments also point residents to low-cost or free kits. That does not replace a certified measurement when a transaction or mitigation decision requires one.

2. Continuous radon monitor (CRM)

A CRM is an electronic device that records radon, often hourly, for at least 48 hours. It can show whether levels were stable or whether someone opened windows or otherwise disturbed the test. Many certified measurement professionals use CRMs. Some homeowners rent or buy consumer-grade continuous monitors; those are useful for screening but are not a substitute for a device and protocol accepted by your state program when a certified result is required.

If you buy a consumer device

If you buy a consumer kit, two common options are below. These are screening devices, not a certified measurement for a real-estate contract. First Alert’s included lab analysis is not available at the cheap DIY price in New Jersey.

Lab fee usually included on charcoal kits (check NJ). Screening only — not a real-estate addendum.

Short-term charcoal

First Alert RD1

Mail-in snapshot, typically 2–4 days in the home. Lab fee is included except for NJ. Use this when you want a first look and can keep the house closed.

First Alert RD1 short-term charcoal kit (paid link)

Continuous monitor

Airthings Corentium Home

Consumer digital screen, short- and long-term averages, no lab. Useful for screening; not a substitute for a state-accepted professional test when a transaction requires one.

Airthings Corentium Home continuous monitor (paid link)

As an Amazon Associate, Shortell Designs earns from qualifying purchases. Tag radontestinde-20. State radon programs, the American Lung Association, and Kansas State’s National Radon Program Services also sell or give kits.

Continuous radon monitor option

Sun Radon lüft (LUFT) plug-in monitor

A continuous monitor shows radon readings over time instead of the single result a one-time short-term kit gives you. According to Sun Radon’s product page, the lüft plugs into a standard wall outlet (no batteries), measures radon along with VOCs, eCO₂, temperature, pressure, and humidity, connects to 2.4 GHz Wi-Fi, and shows readings, trend charts, and alerts in its iOS and Android apps. Like any consumer monitor, treat it as screening and trend watching, not a substitute for a certified test when a sale, lender, or post-mitigation check requires one.

See the Sun Radon lüft radon monitor (affiliate link)

Affiliate link: Shortell Designs may earn a commission from Sun Radon at no extra cost to you. Source: Sun Radon product page (linked above), checked October 5, 2026.

EPA measurement protocols treat a qualified continuous monitor as a valid short-term method when it logs data for the required period (minimum 48 hours, with enough contiguous usable hours).

3. Hiring a certified measurement professional

A state-certified or nationally proficient tester places and retrieves the device, follows closed-building protocols, and reports the result. Hire one when:

The home is under contract (buyers and lenders often require a professional test).
You need a result that will stand up in a real-estate addendum.
The building is large, unusual, or already has a mitigation system (post-mitigation test).
You cannot keep the house closed or be present to start and stop a kit.

EPA tells the public to use the state radon program list first, then the two national proficiency programs EPA recognizes: NRPP and NRSB.

Iowa requires HHS certification to test for others. Pennsylvania requires DEP certification (except listed exemptions, such as testing your own building). Ohio requires an ODH radon tester license to offer testing professionally. National NRPP/NRSB credentials are not a substitute for those state licenses.

After the number

Below 4 pCi/L: EPA still notes some risk. You may retest later (after renovations, or every few years). Consider reducing if you are between 2 and 4 pCi/L.
At or above 4 pCi/L: Confirm with a follow-up test, then hire a credentialed mitigator if the confirmed level stays at or above 4 pCi/L. Do not base a mitigation contract on one unconfirmed kit if you can retest.
After a system is installed, retest to see whether the level dropped. EPA’s consumer mitigation booklet is A Consumer’s Guide to Radon Reduction.

After you know the testing steps, compare kit types side by side before you buy. charcoal kit vs continuous monitor: which DIY radon test fits your home?

find a certified radon tester by state

What this site does not do

Radon Test Index lists people who appear on official certification or license sources. It does not rank contractors or take referral fees on those lists. DIY kit links on this how-to page are Amazon Associates Special Links; we may earn from qualifying purchases. The lüft monitor link is a Sun Radon affiliate link; Shortell Designs may earn a commission from Sun Radon at no extra cost to you. Always verify a professional’s credential is still current with the issuing agency.

National Radon Information Line: 1-800-SOS-RADON (1-800-767-7236).