Radon test result

Bequerels; I suspect this will be 320 Bequerels per cubic metre, meaning that each cubic metre of air contains 320 radon atoms decaying per second. (In general 1 Bequerel just means a quantity of any radioactive material in which one atom decays per second).

Others will advise you on action, but I'd comment that it's not very much above the action limit. There's a tendency for people to regard government "limits" for all sorts of pollutents as "danger limits", e.g. 199 is "safe" and 201 is an immediate threat to life and limb. In fact the limits are usually levels where the risk is very small compared to other natural risks.

Very easy to bring the level down (if you feel this is necessary; but that's a different story) by increasing the ventilation. What are the current ventilaltion arrangements for each room?

Normal BCO resolution in cases like this is to insist on suspended floors with underfloor vents I believe.

Its a bit of a pain to mod an existing house.

I guess most comes up from the ground, but what about walls made of that nice cornish granite? Ventilation is the way to deal with it though.

Maybe we need more info from the OP. Type/age of house, floor construction, recently fitted DG'ing etc. I'd have thought any moderately recent place with a solid floor would have a plastic DPM these days. Can Radon get through plastic DPM?

The reason suspended floors with a 'sump' arrangement work is because radon is very heavy, and will collect at the lowest point - even if it is coming from the walls.

Agreed - far more practical to install in an existing house.

Only to a small degree.

I think that the walls are not the usual major problem. IIRC its more a question of it seeoping up from the ground.

Not that well, no, but that raises the concentrations under it so any small leak...

Ah. I hadn't thought that through. It has to be heavy, being radioactive...

It's usually large atoms that are unstable.

Not necessarily, Tritium isn't.

See the information on

Radioactive nuclei are radioactive because they are effing big and disintegrate.

All radioactive elements are HEAVY.

Its ALWAYS large atoms that are unstable.

Tritium is not IIRC radioactive...

On investigation, you are right. Tritium is both light and radioactive, It also has a half life measured in days, so poses very little hazard.

Perhaps I should have said more exactly that 'any radioactive element with a sufficient half life to actually be present and represent a risk to health will be very heavy'

Tritium only occurs naturally AFAICT on account of cosmic ray bombardment. It decays as fast as it is produced.

Tritium?

No, really, it is.

others: 4500+/-8 days.

This will be a different kind of tritium, then, from the stuff in the Traser key-tags in my pockets, will it? Ummm...

That covers you for the many radioactive isotopes of common elements then (C13, N15 etc).