ActSmall · Ground

Test your home for radon

A short-term home radon test is the smallest, cheapest, most replicable household-radiation action available. The test costs $15-30, runs for 2 to 7 days on the lowest lived-in level of your home, and tells you in Bq/m3 or pCi/L whether your house is one of the affected ones.

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Why this works

National averages tell you the prior probability for the country you live in. They do not tell you whether your house is one of the affected ones. Radon concentration varies on the order of 100x between individual homes on the same street, depending on the basement-to-foundation seal, the type of underlying rock, whether the house is on a slab or has a crawl space, the heating/ventilation system, and seasonal effects. The only way to know your house is to measure it.

The detector itself is passive: a small plastic cup with a strip of CR-39 polycarbonate or a charcoal canister inside. You leave it sitting out on a shelf for the recommended exposure period; alpha particles from radon daughters score the detector. The certified lab reads the score and computes the average concentration over the exposure window.

What you need

  • One short-term radon test kit ($15-30 in most affected countries). Order from a certified national source (list below) or from an AARST/UKHSA-certified retailer. Avoid generic online resellers - certification means the lab returning the result is accredited.
  • A spot on the lowest lived-in level of your home where the detector can sit undisturbed for the test period - usually a basement living room shelf, a ground-floor bedroom, or a similar space. Not a bathroom (humidity skews short-term kits), not a kitchen (cooking exhaust), not next to a draft, not in direct sunlight.
  • A return envelope (the kit ships with one) and the return postage.

How to run the test

  1. Open the kit and record the start time. Most kits include a small log sheet; some have a barcode you scan with the lab's app instead.
  2. Place the detector on a stable surface at about chest height, away from drafts and direct sunlight. Avoid kitchens, bathrooms, and other high-moisture rooms - they bias the result.
  3. Live normally. Do not open extra windows or run extra fans for the test period; the point is to measure the indoor concentration under your normal living pattern.
  4. At the end of the test period (typically 2-7 days for a short-term kit, longer for a long-term track-etch detector), close the detector, fill in the end-time on the log sheet, drop it in the return envelope, and post it.
  5. The lab reads the detector and emails or posts the result in about 1-3 weeks. The result is a single number in Bq/m3 (metric) or pCi/L (US): 1 pCi/L = 37 Bq/m3.

What the number means

The reference levels published by the named authorities:

  • WHO global reference: 100 Bq/m3. The World Health Organization recommends action above this level.
  • National references: the US EPA action level is 4 pCi/L (148 Bq/m3); the UKHSA, Ireland, Sweden, Norway, Latvia, Lithuania, New Zealand, Australia, and Canada use 200 Bq/m3; Germany, France, the Czech Republic, and several other EU member states use 300 Bq/m3. The references differ because they are calibrated to different national survey distributions, not because the underlying physics differs.

If your reading is well below the national reference, you are done. Many homes test very low and never need to test again.

If your reading is between roughly half the national reference and the reference itself, most national programs recommend a follow-up long-term test (a track-etch detector left out for 3-12 months) to even out seasonal variability before deciding on mitigation.

If your reading is above the national reference, the action is to consult a certified radon-mitigation professional. The lists below include the relevant certifications by country. Mitigation in a typical residential building is well-understood engineering - usually a sub-slab depressurisation system with a small continuous-running fan - and costs roughly $500-1,500 in most affected countries.

Where to order the kit

If you cannot buy a kit where you live

Some countries do not yet have a national radon programme or a domestic certified-lab pipeline. In those cases, kits can be ordered internationally from UK or US suppliers; the lab still reads the detector and posts back the result. The lab does not need to be in the same country as the home being tested.

Citizen-published readings in under-surveyed countries become small but real public data points. If you do test your home in a country without a national programme, consider publishing the result (with the rough geography) somewhere a researcher could find it - a local newspaper letter, a personal blog post, an open civic-data project, or a peer-network mailing list.

What this is not

It is not mitigation advice. If your reading is above the national reference, the action is to consult a certified mitigation professional - not to start sealing your basement yourself based on what you read online. Mitigation engineering is a regulated trade in most affected countries because the wrong intervention can make readings worse (closing off air paths can concentrate the gas), and getting it right requires standardised post-mitigation testing.

It is not medical advice. Reading a Bq/m3 number does not tell you anything actionable about a specific clinical decision; that conversation is with your clinician.

This project card is published under CC BY-SA 4.0. Print, copy, translate, and adapt freely; please keep the source citations intact.