dpb wrote:
On 09/29/2014 3:03 PM, Bob wrote:
Hello,

Anyone know of any Links where there is information regarding
how safe an Ionization type of Smoke Detector is in a youngster's room.

Looked, but couldn't really find anything specific.
...

You'd have difficulty in discerning its presence at any distance from
natural background radiation without very good measurement technique.

The 241Am isotope used is primarily an alpha emitter and the range of
alpha particles is only a few inches in free air plus they can't even
penetrate a single sheet of paper owing to their size and charge (they're
a He atom w/o the two electrons so have +2 proton charge).

There's a plethora of gammas, but the dominant is only about 60 keV which
is pretty weak and the overall source intensity of a typical detector
source is only about one microcurie, and the exposure as long as you
don't remove the source from the device would be less than about 1/100 of
a millirem per year.

To put that in context, average background in the US is about 300 mrem/yr.

In order to even know the device was in the room from any practical
standpoint of concern you'd have to remove the source from the device
itself and bring it near you and keep it there indefinitely. Even then
your exposure would be under any occupational or general public limits.

Annual Radiation Dose Limits Agency

Radiation Worker €“ 5 rem (NRC, "occupationally" exposed)
General Public €“ 100 mrem (NRC, member of the public)

General Public €“ 10 mrem (EPA, air pathway)

At roughly 0.01 mrem from the device, you can see the fractional
relationship to established exposure limits is in the noise level.

Upshot--don't worry about it; radon even with a mitigation system is
likely _far_ higher than the amount given off by the smoke detector. Or,
as another comparison -- would you not take a transcontinental air trip
over concern for the extra radiation dose you'd give the infant? That
would add from 0.1-0.5 mrem/hr depending on the route (higher on polar,
higher elevation long-haul routes), roughly 10-50X the exposure rate from
the smoke detector.

--

I have an old baby Ben clock I now use for a radiation calibrator. Used to
sleep next to it. Second most powerful radiator in my house. An old pentax
lens has the highest count with uranium oxide coating.

Greg