The search says the property is in a radon affected area

Measuring it

A radon measurement uses detectors left in the house for a period, because levels fluctuate. It is inexpensive and it is the only thing that produces an actual answer.

Start by asking whether the property has been tested. A seller is not obliged to volunteer what they know, but if they are asked they must answer, and that asking is routine for a conveyancer. If no test has been done, a radon risk report for the address is the next step and can usually be obtained quickly.

If you want certainty before exchange, a test takes time — which is a reason to raise it early rather than a reason to skip it.

If the level is high

The remedy is usually building work rather than anything dramatic: improving under-floor ventilation, sealing the floor, or fitting a sump that vents gas from beneath the building to outside.

These are established, well-documented measures and they are generally effective and not expensive relative to a house purchase. A high reading is a cost to establish and negotiate, not a reason to abandon a transaction.

The public guidance on radon levels, action levels and remediation is published and free, and your conveyancer's report will usually point you to it.