Ether Jones wrote:

The key word there is "continuously". Unless you sleep in the basement
and plan to stay in this house for 30 years, I wouldn't worry about 4pCi/l

I would, based on the death statistics.

Figures don't lie, but liars can figure.

Follow the money.

... it seems to me this standard should be tightened,
based on the risk and the cost of the fix.

Perhaps we should pass a national law requiring all automobile drivers
to wear crash helmets, based on the risk and the cost of the fix.

The lifetime odds of dying from radon at 4 pCi/l (139:1 for a non-smoker)
are about half the odds of death in a car (228:1), so it's strange that
we've spent double to avoid auto deaths, as PE Drew Gillett points out...

Ah a subject dear to my heart from a former life. (I assisted Terry Brennan
and EPA in some of the PA and NJ original house testing and helped
develop the mitigation methods and courses for radon. The highest house
I dealt with was 400pC/l (successfully reduced below 4, and the highest
exposure I saw was over 10000 pC/l in air above an open well in a basement.)

...The risk for smokers and radon is multiplicative of their smoking risk,
i.e. smokers should definitely not live in a high radon house and vice-
versa (high radon houses should not be sold or rented to smokers).

One of the problems is that the data indicate that if radon were to be
federally controlled to levels consistent with risk from other hazards,
it would have to be at below the outdoor level (which varies with height
above ground. "Your mother told you not to lie on the grass. Why didn't
you listen?")

The 4 was picked as a reasonable level to obtain for a reasonable cost
for a reasonable number of homes without panicking the public or busting
the budget... not that based on the hazard and the risk and the cost of
mitigation to that level... we should indeed be controlling it to below
.4 pC/l for the average public.

The scary part is the 10000 to 40000 excess lung cancer deaths per year.
on the order of car accidents, etc. If we can put $2000 airbags in cars,
we ought to be able to put $2000 radon systems in houses for similar
reductions in premature death...

Sealing by itself is not effective, but is necessary and helpful in
conjunction with other methods, sub-slab suction, air to air htx and
submembrane suction and passive stacks.

Rather than run the fan intermittently (which would still allow some
radon in), just run it continuously at a speed (controlled) enough to
maintain the delta pressure across the floor so all airflow is out of
the building (in southern climes this gets into a moisture problem,
but not typically.)

The EPA is apparently still looking into electronic air cleaners, which
can't reduce the gas concentration but can reduce the solid daughters of
radon particles in house dust that get into our lungs and cause problems.
I like the Envirosept charged-media filter, which uses a lot less power
(under 2 watts) than a HEPA filter.

Nick