Radon

What should you do with a radon result that sits between 100 and 200 Bq/m3?

Read it against both published levels. The Target Level is 100 Bq/m3. The Action Level is 200 Bq/m3 as an annual average. UKradon says that between them, action to reduce the level should be considered, especially where someone in the home smokes or used to smoke. It does not say the house has failed a survey, because a survey did not produce this number.

Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.

What is the fuller explanation?

The result only means that if it came from the three-month, two-detector method. A map, an address search or a short reading is not an annual average. Do not average those different products into one figure and call it the Action Level.

Reduction work is designed after you know the level and the floors. This page does not give a price for a sump or a fan. Anyone who prices one from the postcode alone is guessing. The home survey, if it mentions radon at all, should send you to a measurement rather than invent a rating from a colour.

What should you ask your surveyor?

Is the figure an annual-average test, or something else?
Does anyone who will live there smoke, or used to?
Has the survey confused this number with a condition rating?

What are the typical next steps?

Keep the laboratory sheet, not a sentence in an email.
Decide whether to consider reduction, using UKradon’s own wording, before you ask the seller for money.
Do not convert 100 or 200 into a percentage of the purchase price.

Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.

Also asked about this

Does under 100 mean you can stop thinking about it?

UKradon describes 100 as the ideal outcome, not as a promise the level will never change if you alter the floors. It is still a measurement, not a map.

Is 200 a legal ban on living in the house?

It is the level above which UKHSA recommends reduction. It is not a condition rating and not an eviction notice in the survey.